CHAPTER 1

INTRODUCTION

In general, this chapter will explain about the identification of the Development of Universal Asynchronous Receiver/ Transmitter using Verilog HDL. At the beginning of this chapter, some introduction of this project will be implemented to get the full understanding about this project. The project background will be explained in this chapter to clarify the basic idea about this project. In addition the project statement, objective of the project, scope of project / limitation and summary of chapter are also been explained to make it more clearly about this project.

A Universal Asynchronous Receiver/Transmitter is a piece of computer hardware that translates data between parallel and serial forms. UARTs are commonly used in conjunction with communication standards such as EIA, RS-232, RS-422 or RS-485. The universal designation indicates that the data format and transmission speeds are configurable. The electric signaling levels and methods such as differential signaling are handled by a driver circuit external to the UART. A UART is usually an individual (or part of an) integrated circuit used for serial communications over a computer or peripheral device serial port. UARTs are now commonly included in microcontrollers. A dual UART, or DUART, combines two UARTs into a single chip. Many modern ICs now come with a UART that can also communicate synchronously these devices are called USARTs (Universal Synchronous/Asynchronous Receiver/ Transmitter).

The Universal Asynchronous Receiver/Transmitter (UART) takes bytes of data and transmits the individual bits in a sequential fashion. At the destination, a second UART re-assembles the bits into complete bytes. Each UART contains a shift register, which is the fundamental method of conversion between serial and parallel forms. Serial transmission of digital information (bits) through a single wire or other medium is less costly than parallel transmission through multiple wires. The UART usually does not directly generate or receive the external signals used between different items of equipment. Separate interface devices are used to convert the logic level signals of the UART to and from the external signaling levels. External signals may be of many different forms. Examples of standards for voltage signaling are RS-232, RS-422 andRS-485 from the EIA. Historically, current (in current loops) was used in telegraph circuits. Some signaling schemes do not use electrical wires. Examples of such are optical fiber, IrDA (infrared), and (wireless) Bluetooth in its Serial Port Profile (SPP). Some signaling schemes use modulation of a carrier signal (with or without wires). Examples are modulation of audio signals with phone line modems, RF modulation with data radios, and the DC-LIN for power line communication.

1.1 PROJECT BACKGROUND

Abbreviation for Universal Asynchronous Receiver-Transmitter, UART is a chip used to manage computer serial ports, disk drive interrupts, screen refresh cycles, and any other device that requires timing. With a serial port transmission, the UART converts the bytes into serial bits and transmits those bits through an asynchronous transmission, stripping out the start and stop bits for each character. Below is a listing of various UART chips. The 16550 chip series is the most commonly used UART. The Universal Asynchronous Receiver Transmitter (UART) is a popular and widely-used device for data communication in the field of telecommunication. A UART is the microchip with programming that controls a computer's interface to its attached serial devices. Specifically, it provides the computer with the RS-232 Data Terminal Equipment (Data Terminal Equipment ) interface so that it can communicate to and exchange data with modems and other serial devices. More advanced UARTs provide some amount of buffer of data so that the computer and serial devices data streams remain coordinated. The most recent UART, the 16550, has a 16-byte buffer that can get filled before the computer's processor needs to handle the data. The original UART was the 8250. If you purchase an internal modem today, it probably includes a 16550 UART (although you should ask when you buy it). According to modem manufacturer robotics, external modems do not include a UART. For an older computer, we as user want to add an internal 16550 to get the most out of the external modem.

A Universal Asynchronous Receiver/Transmitter, is a piece of computer hardware that translates data between parallel and serial forms. UARTs are commonly used in conjunction with communication standards such as EIA, RS-232, RS-422 or RS-485. The universal designation indicates that the data format and transmission speeds are configurable. The electric signaling levels and methods such as differential signaling are handled by a driver circuit external to the UART. A UART is usually an individual (or part of an) integrated circuit used for serial communications over a computer or peripheral device serial port. UARTs are now commonly included in microcontrollers. A dual UART, or DUART, combines two UARTs into a single chip. Many modern ICs now come with a UART that can also communicate synchronously these devices are called USARTs (Universal Synchronous/ Asynchronous Receiver/ Transmitter).

1.2 PROJECT STATEMENT

The purpose of this project is to develop UART controller interface. A Universal Asynchronous Receiver/ Transmitter (UART) is a hardware that translates data between parallel and serial forms. UART is used for serial communications over a computer or peripheral device serial port. UART are commonly used in conjunction with communication standards such as RS-232 or RS-422. Uart is commonly included in microcontrollers. This project will be implemented using Verilog HDL. Then it will programmed into Altera DE2 board using for proof of concept.

1.2.1 Receiver

All operations of the UART hardware are controlled by a clock signal which runs at a multiple of the data rate. For example, each data bit may be as long as 16 clock pulses. The receiver tests the state of the incoming signal on each clock pulse, looking for the beginning of the start bit. If the apparent start bit lasts at least one-half of the bit time, it is valid and signals the start of a new character. If not, the spurious pulse is ignored. After waiting a further bit time, the state of the line is again sampled and the resulting level clocked into a shift register. After the required number of bit periods for the character length (5 to 8 bits, typically) have elapsed, the contents of the shift register is made available (in parallel fashion) to the receiving system. The UART will set a flag indicating new data is available, and may also generate a processor interrupt to request that the host processor transfers the received data.

The best UARTs "resynchronize" on each change of the data line that is more than a half-bit wide. In this way, they reliably receive when the transmitter is sending at a slightly different speed than the receiver. (This is the normal case, because communicating units usually have no shared timing system apart from the communication signal.) Simplistic UARTs may merely detect the falling edge of the start bit, and then read the center of each expected data bit. A simple UART can work well if the data rates are close enough that the stop bits are sampled reliably.

It is a standard feature for a UART to store the most recent character while receiving the next. This "double buffering" gives a receiving computer an entire character transmission time to fetch a received character. Many UARTs have a small first-in, first-out FIFO buffer memory between the receiver shift register and the host system interface. This allows the host processor even more time to handle an interrupt from the UART and prevents loss of received data at high rates.

1.2.2 Transmitter

Transmission operation is simpler since it is under the control of the transmitting system. As soon as data is deposited in the shift register after completion of the previous character, the UART hardware generates a start bit, shifts the required number of data bits out to the line, generates and appends the parity bit (if used), and appends the stop bits. Since transmission of a single character may take a long time relative to CPU speeds, the UART will maintain a flag showing busy status so that the host system does not deposit a new character for transmission until the previous one has been completed; this may also be done with an interrupt. Since full-duplex operation requires characters to be sent and received at the same time, UARTs use two different shift registers for transmitted characters and received characters.

1.3 PROBLEM STATEMENT

This project attempts to develop an UART interface using Verilog HDL. In telecommunications, RS-232 (Recommended Standard 232) is a standard for serial binary single-ended data and control signals connecting between a DTE (Data Terminal Equipment) and a DCE (Data Circuit-terminating Equipment). It is commonly used in computer serial ports. A similar ITU-T standard is V.24.

When developing or troubleshooting systems using RS-232, close examination of hardware signals can be important to find problems. A serial line analyzer is a device similar to a logic analyzer but specialized for RS-232's voltage levels, connectors, and, where used, clock signals. The serial line analyzer can collect, store, and display the data and control signals, allowing developers to view them in detail. Some simply display the signals as waveforms; more elaborate versions include the ability to decode characters in ASCII or other common codes and to interpret common protocols used over RS-232 such as SDLC, HDLC, DDCMP, and X.25. Serial line analyzers are available as standalone units, as software and interface cables for general-purpose logic analyzers, and as programs that run in common personal computers.

1.4 OBJECTIVES OF THE PROJECT

The objectives of the proposed project, Development of Universal Asynchronous Receiver/ Transmitter are;

To design a serial asynchronous receiver and transmitter communication with standard I/O serial devices.
To design a UART that can be prototyping Altera DE2, then testing and debugging the prototype in system.
To analyze the features of UART technology and make comparison with other existing UART technology.
To implement the asynchronous receiver-transmitter in Altera DE2 board to achieve fast prototyping and design verification.
To learn and expertise using Verilog HDL and Altera DE2.

1.5 SCOPE OF PROJECT/LIMITATION

In order to achieve the objective of this project, there are several scope had been outlined. The application of RS-232 has extended far beyond the original purpose of interconnecting a terminal with a modem, successor standards have been developed to address the limitations. The scope of this project includes:

1.5.1 Large Voltage Swings

The need for higher voltage swings in applications such as test-and-measurement instruments is constantly increasing, but the power supplies impose limitations on the operational amplifier rails make the high-voltage need a challenge for designers. We must deliver high-voltage swings to a load without increasing the voltage levels of the power supplies of the operational amplifier. In other words, for example, we produce a ±16V or greater signal swing across the load using only ±15V power supplies. The circuit uses a fully differential amplifier to offer an answer to this problem. Fully differential amplifiers enable you to deliver an output-voltage swing beyond the rails into the load. One of the common problems in working with operational amplifiers is the limit that the power-supply rails impose. The standard since the days of analog computers has been ±15V. Analog computers are gone, but their legacy remains in the power-supply voltages. These voltages find widespread use in transducer interfaces and applications in which voltage swing and dynamic range are of primary importance.

1.5.2 Single-ended Signaling

Single-ended signaling is the simplest and most commonly used method of transmitting electrical signals over wires. One wire carries a varying voltage that represents the signal, while the other wire is connected to a reference voltage, usually ground. The main alternative to single-ended signaling is called differential signaling. There is also the historic alternative of ground return, rarely used today. Single ended signaling is less expensive to implement than differential, but it lacks the ability to reject noise caused by differences in ground voltage level between transmitting and receiving circuits and induction picked up on the signal wire. The main advantage of single-ended over differential signaling is that fewer wires are needed to transmit multiple signals. If there are n signals, then there are n+1 wires - one for each signal and one for ground. Differential signaling uses at least 2n wires. A disadvantage of single-ended signaling is that the return currents for all the signals share the same conductor even if separate ground wires are used, the grounds are inevitably connected together at each end and this can sometimes cause interference crosstalk between the signals.

1.5.3 Propogation Delays

In electronics, digital circuits and digital electronics, the propagation delay, or gate delay, is the length of time which starts when the input to a logic gate becomes stable and valid, to the time that the output of that logic gate is stable and valid. Often this refers to the time required for the output to reach from 10% to 90% of its final output level when the input changes. Reducing gate delays in digital circuits allows them to process data at a faster rate and improve overall performance.

The difference in propagation delays of logic elements is the major contributor to glitches in asynchronous circuits as a result of race conditions.

The principle of logical effort utilizes propagation delays to compare designs implementing the same logical statement. Propagation delay increases with operating temperature, marginal supply voltage as well as an increased output load capacitance. The latter is the largest contributor to the increase of propagation delay. If the output of a logic gate is connected to a long trace or used to drive many other gates high fanout the propagation delay increases substantially.

1.5.4 Multi-drop Connection

A multidrop bus (MDB) is a computer bus in which all components are connected to the electrical circuit. A process of arbitration determines which device sends information at any point. The other devices listen for the data they are intended to receive. Multidrop buses have the advantage of simplicity and extensibility. However, modern SDRAM chips exemplify the problem of electrical impedance discontinuity.Fully Buffered DIMM is an alternative approach to connecting multiple DRAM modules to a memory controller. Since 2000, multidrop standards such as PCI and Parallel ATA are increasingly being replaced by point-to-point systems such as PCI Express and SATA.

1.5.5 Asymmetrical definitions

Asymmetrical definitions of the two ends of the link make the assignment of the role of a newly developed device problematic; the designer must decide on either a DTE-like or DCE-like interface and which connector pin assignments to use.

Limitation of the project is at market segment. The usages of the project are mostly for lecturer or laboratory examiner only. It needs electronics knowledge to determine the data.

1.6 SUMMARY OF THE CHAPTER

This chapter focuses on the introduction to this project and the objectives of this project. This chapter briefly explained about the introduction of this project, project background, project statement, objective and scope of project. In conclusion, this chapter gives more details about this project.

CHAPTER 2

LITERATURE REVIEW

2.1 HISTORY

Some early telegraph schemes used variable-length pulses (as in Morse code) and rotating clockwork mechanisms to transmit alphabetic characters. The first UART-like devices (with fixed-length pulses) were rotating mechanical switches (commutators). Various character codes using 5, 6, 7, or 8 data bits became common in teleprinters and later as computer peripherals. Gordon Bell designed the UART for the PDP series of computers. The teletypewriter made an excellent general-purpose I/O device for a small computer. To reduce costs, including wiring and back-plane costs, these computers also pioneered flow control using XON and XOFF characters rather than hardware wires.

Western Digital made the first single-chip UART WD1402A around 1971; this was an early example of a medium scale integrated circuit. Another popular chip was a SCN2651 from the Signetics 2650 family.

An example of an early 1980s UART was the National Semiconductor 8250. In the 1990s, newer UARTs were developed with on-chip buffers. This allowed higher transmission speed without data loss and without requiring such frequent attention from the computer. For example, the popular National Semiconductor 16550 has a 16 byte FIFO, and spawned many variants, including the 16C550, 16C650, 16C750, and 16C850.

Depending on the manufacturer, different terms are used to identify devices that perform the UART functions. Intel called their 8251 device a "Programmable Communication Interface". MOS Technology 6551 was known under the name "Asynchronous Communications Interface Adapter" (ACIA). The term "Serial Communications Interface" (SCI) was first used at Motorola around 1975 to refer to their start-stop asynchronous serial interface device, which others were calling a UART.

2.1.1 RS232 port.

RS-232 was first introduced in 1962 by the Radio Sector of the EIA.The original DTEs were electromechanical teletypewriters, and the original DCEs were (usually) modems. When electronic terminals (smart and dumb) began to be used, they were often designed to be interchangeable with teletypewriters, and so supported RS-232. The C revision of the standard was issued in 1969 in part to accommodate the electrical characteristics of these devices.

Since the requirements of devices such as computers, printers, test instruments, POS terminals and so on were not considered by the standard, designers implementing an RS-232 compatible interface on their equipment often interpreted the requirements idiosyncratically. Common problems were non-standard pin assignment of circuits on connectors, and incorrect or missing control signals. The lack of adherence to the standards produced a thriving industry of breakout boxes, patch boxes, test equipment, books, and other aids for the connection of disparate equipment. A common deviation from the standard was to drive the signals at a reduced voltage. Some manufacturers therefore built transmitters that supplied +5 V and -5 V and labeled them as "RS-232 compatible".

Later personal computers (and other devices) started to make use of the standard so that they could connect to existing equipment. For many years, an RS-232-compatible port was a standard feature for serial communications, such as modem connections, on many computers. It remained in widespread use into the late 1990s. In personal computer peripherals, it has largely been supplanted by other interface standards, such as USB. RS-232 is still used to connect older designs of peripherals, industrial equipment (such as PLCs),console ports and special purpose equipment.

The standard has been renamed several times during its history as the sponsoring organization changed its name, and has been variously known as EIA RS-232, EIA 232, and most recently as TIA 232. The standard continued to be revised and updated by the Electronic Industries Alliance and since 1988 by the Telecommunications Industry Association (TIA).Revision C was issued in a document dated August 1969. Revision D was issued in 1986. The current revision is TIA-232-F Interface Between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange, issued in 1997. Changes since Revision C have been in timing and details intended to improve harmonization with the CCITT standard V.24, but equipment built to the current standard will interoperate with older versions.

Related ITU-T standards include V.24 (circuit identification) and V.28 (signal voltage and timing characteristics).

In revison D of EIA-232, the D-subminiature connector was formally included as part of the standard (it was only referenced in the appendix of RS 232 C). The voltage range was extended to +/- 25 volts, and the circuit capacitance limit was expressly stated as 2500 pF. Revision E of EIA 232 introduced a new, smaller, standard D-shell 26-pin "Alt A" connector, and made other changes to improve compatibility with CCITT standards V.24, V.28 and ISO 2110.

2.1.2 Altera DE2 board.

Altera Corporation is a Silicon Valley manufacturer of PLDs, reconfigurable complex digital circuits. The company released its first PLD in 1984.Altera's main products are the Stratix, Arria and Cyclone series FPGAs, the MAX series CPLDs (Complex programmable logic devices),the HardCopy series ASICs and Quartus II design software.

2.1.3 FPGA

The Stratix series FPGAs are the company's largest, highest bandwidth devices, with up to 1.1 million logic elements, integrated transceivers at up to 28 Gbit/s, up to 1.6 Tbit/s of serial switching capability, up to 1,840 GMACs of signal-processing performance, and up to 7 x72 DDR3 memory interfaces at 800 MHz. Cyclone series FPGAs and SoC FPGAs are the company's lowest cost, lowest power FPGAs, with variants offering integrated transceivers up to 5 Gbit/s. In between these two device families are Arria series FPGAs and SoC FPGAs, which provide a balance of performance, power, and cost for mid-range applications such as remote radio heads, video conferencing equipment, and wireline access equipment. Arria FPGAs have integrated transceivers up to 10 Gbit/s. In December 2012, the company announced that they are shipping their first 28nm SoC FPGA devices.According to Altera, fully depleted silicon on insulator (FDSOI) chip manufacturing process is benefitial for FPGAs.

2.1.4 ASIC

Altera offers a design flow based on HardCopy ASICs, which transitions the FPGA design, once finalized, to a form which is not alterable. This design flow reduces design security risks as well as costs for higher volume production. Design engineers can prototype their designs in Stratix series FPGAs, and then migrate these designs to HardCopy ASICs when they're ready for volume production.

The unique design flow makes hardware/software co-design and co-verification possible. The flow has been benchmarked to deliver systems to market 9 to 12 months faster, on average, than with standard-cell solutions. Design engineers can employ a single RTL, set of intellectual property (IP) cores, and Quartus II design software for both FPGA and ASIC implementations. Altera's HardCopy Design Center manages test insertion.

2.1.5 Verilog HDL

In 1970''s when IC fabrication was in the primitive stages then designers were doing the digital design using schematics. But then the design complexity has risen exponentially. So in order to keep up with the designing complex circuits, electronics and electrical engineers were looking for some alternative way of defining the hardware. Thus born is the (Hardware description Language) HDL''s. There are many HDLs now and the popular HDLs are VHDL, Verilog and systemC.

These HDL''s are different from the usual computer languages from the way it is executed. Computer languages like C, C++ are sequentially executed whereas HDL''s are executed concurrently. By concurrent we refer to the way the statements are executed. Hardwares are not executed sequentially like a c program instead many blocks of the design work in parallel, so concurrent execution is a must. VHDL is a project of DARPA and Verilog HDL is from the Gateway design Automation (GDA). Cadence acquired GDA and released the language in the public domain and thus the popularity of the language grew rapidly. Thus many fabrication companies around the world supported verilog libraries thus making even more popular.
There are many simulators available on the internet and the best for a student is Modelsim from Mentor Graphics. Verilog has many advantages over VHDL, one of them being the similarity with C language. In order to build a good command over the design we build, it is important digital design fundamentals are proper. Once this is over then rest is learning the syntax of the language and make a succesful design. A good reference book to verilog language can be "Verilog HDL by Samir Palnitkar", "HDL design by Douglas J Smith", Verilog HDL by Phil Moorby(Original verilog HDL architect with GDA) and the Language reference manual(LRM). Verilog is a verilfication language and hence have rich capabilities for testing. PLI(programming Language Interface) which gives the added flexibility in testing and verification for the code written in C and then to be integrated with HDL code. Another flexible feature is UDP which stands for User Defined Primitives.

Verilog was the first modern hardware description language to be invented. It was created by Phil Moorby and Prabhu Goel during the winter of 1983/1984. The wording for this process was "Automated Integrated Design Systems" (later renamed to Gateway Design Automation in 1985) as a hardware modeling language. Gateway Design Automation was purchased by Cadence Design Systems in 1990. Cadence now has full proprietary rights to Gateway's Verilog and the Verilog-XL, the HDL-simulator that would become the de facto standard (of Verilog logic simulators) for the next decade. Originally, Verilog was intended to describe and allow simulation; only afterwards was support for synthesis added.

2.2 Previous Work

2.2.1 Embedded System

The purpose of this study was to interface at all dedicated only to one task to complex graphical user interfaces that resemble modern computer desktop operating systems. Simple embedded devices use buttons, LEDs, graphic or character LCDs (for example popular HD44780 LCD) with a simple menu system. More sophisticated devices which use a graphical screen with touch sensing or screen-edge buttons provide flexibility while minimizing space used: the meaning of the buttons can change with the screen, and selection involves the natural behavior of pointing at what's desired. Handheld systems often have a screen with a "joystick button" for a pointing device.

Some systems provide user interface remotely with the help of a serial (e.g. RS-232, USB, I²C) or network (Ethernet) connection. This approach gives several advantages: extends the capabilities of embedded system, avoids the cost of a display, simplifies BSP, allows us to build rich user interface on the PC. A good example of this is the combination of an embedded web server running on an embedded device (such as an IP camera) or a network routers. The user interface is displayed in a web browser on a PC connected to the device, therefore needing no bespoke software to be installed.

An embedded system is a computer system designed for specific control functions within a larger system, often with real-time computing constraints. It is embedded as part of a complete device often including hardware and mechanical parts. By contrast, a general-purpose computer, such as a personal computer (PC), is designed to be flexible and to meet a wide range of end-user needs. Embedded systems control many devices in common use today. Embedded systems contain processing cores that are either microcontrollers or digital signal processors (DSP). A processor is an important unit in the embedded system hardware. It is the heart of the embedded system.

The key characteristic, however, is being dedicated to handle a particular task. Since the embedded system is dedicated to specific tasks, design engineers can optimize it to reduce the size and cost of the product and increase the reliability and performance. Some embedded systems are mass-produced, benefiting from economies of scale. Physically, embedded systems range from portable devices such as digital watches and MP3 players, to large stationary installations like traffic lights, factory controllers, and largely complex systems like hybrid vehicles, MRI, and avionics. Complexity varies from low, with a single microcontroller chip, to very high with multiple units, peripherals and networks mounted inside a large chassis or enclosure.

2.2.2 Development Board: Wireless Transceiver

Figure 2.2.2a: Wireless Transceivers.

Features

· Running frequency: 915M，2.5K Frequency Step.

· 64 channels setting, non-volatile on power off, Transmitting power: 7dBm

· Receiving sensitivity: －109dBm

· Modulation method: FSK

· Receiving method: Zero IF digital receiving

· Airborne speed rate: 300－19200bps

· Serial port speed rate:19200bps

· Transmitting current: 20－30mA（including MCU）

· Receiving current: 15－20mA（including MCU）

· Standby current: <1ua o:p="">

· Running voltage: 2.8-3.3V

· Communication distance: 250－350m（Notes: the maximum communication distance correlates with environment, antenna form and communication speed rate).

Transmit

Once initialised, transmitting data is quite simple;

1. Ensure TXR Busy pin is HIGH (indicates the module is free to transmit - no incoming/outgoing packets).

2. Send UART data to TXR RXD pin (that's right, data is sent to the RXD pin on the TXR).

3. Wait for 15mS (module will send data automatically after a 10mS delay - 15mS is the recommended wait time).

· Be sure to connect the UART TX pin of the PIC to the RXD pin on the TXR module.

· The TXR module has a 63 byte transmit buffer. You can send 1 byte or 63 bytes - anything after this will be ignored.

· Once data is sent to the TXR, the 15mS delay will initiate the transmit.

· The TXR Busy pin will go high for the duration of the transmit.

· The TXR Busy pin can drive loads upto 20mA. This allows an LED with series resistor to be connected to it. The LED will flash when TX/RX wireless data.

Receiver

Even easier then transmitting, receiving goes like this;

1. Received wireless data will be transmitted from the TXR TXD pin.

Use the hardware UART module/library to ensure no lost/corrupt data.

Program

Naturally, a program says a thousands words. Consider the following TRANSMIT program. Program designed to operate with a 10Mhz external crystal. Also, there is some initialisation code for the development board I made which configures the MAX3223 interface - disregard if just using the TXR.

2.2.3 Wireless Temperature and Humadity Sensor

Figure 2.2.3a: Wireless Temperature and Humadity Sensor

This project is based on the principle of Universal Asynchronous Receiver/ Transmitter (UART) which The temperature and humidity sensor used is an Sensirion SHT15 which I picked-up from Futurelec. The datasheet claims accuracy of ±2.0% for relative humidity measurements and ±0.4°C for temperature measurements. The SHT15 gives 14bit temperature and 12bit humidity readings via a 2-wire serial interface. Unfortunately the interface is not I2C compatible so I had to write a Swordfish module to handle communications between the PIC and the sensor.

XBee RF modules are used to provide the wireless link between the sensor and the base station. The XBee modules are really easy to use they have an integrated antenna and are ready to go straight out the box. Apply power, feed serial data into the UART of one and it comes out the other without any setting-up or tweaking. Multiple XBee modules can be linked together into a Personal Area Network (PAN). Each module in the PAN has its own address and messages can either be broadcast to all modules or addressed to a specific one. The modules will ignore any messages which don’t come from within the PAN. The PAN ID, module address and other settings are configured using AT commands sent through the module’s UART. Swordfish module to handle putting the XBee into AT Command Mode and setting / reading the control parameters. The pins on the XBee modules are 2mm pitch so they can’t be plugged directly into breadboard for prototyping. Also, the modules are 3.3V parts which was a problem for me as I’ve only got 5V PICs to hand. To get around these problems I used a Droids breakout board. The board brings the pins out to a 2.54mm pitch and also includes a 3.3V regulator to power the XBee from a 5V supply.

The XBee’s DataIn and DataOut pins connect to the TX and RX pins of the PIC’s USART. As the XBee is a 3.3V device, a voltage divider brings the 5V output of the PIC’s TX pin down to a level which the XBee can handle. The RX pin on the PIC is connected directly to the DataOut of the XBee. The only other connection to the PIC is the XBee’s Sleep pin which is used to put it into a low power mode between transmissions.

2.3 Present Work

It is the recent development of The Universal Asynchronous Receiver/Transmitter (UART) controller is the key component of the serial communications subsystem of a computer. The UART takes bytes of data and transmits the individual bits in a sequential fashion. At the destination, a second UART re-assembles the bits into complete bytes. Serial transmission is commonly used with modems and for non-networked communication between computers, terminals and other devices. There are two primary forms of serial transmission: Synchronous and Asynchronous. Depending on the modes that are supported by the hardware, the name of the communication sub-system will usually include A if it supports Asynchronous communications and S if it supports Synchronous communications.

2.4 Asynchronous Serial Transmission

Asynchronous transmission allows data to be transmitted without the sender having to send a clock signal to the receiver. Instead, the sender and receiver must agree on timing parameters in advance and special bits are added to each word which are used to synchronize the sending and receiving units.

When a word is given to the UART for Asynchronous transmissions, a bit called the "Start Bit" is added to the beginning of each word that is to be transmitted. The Start Bit is used to alert the receiver that a word of data is about to be sent, and to force the clock in the receiver into synchronization with the clock in the transmitter. These two clocks must be accurate enough to not have the frequency drift by more than 10% during the transmission of the remaining bits in the word. (This requirement was set in the days of mechanical teleprinters and is easily met by modern electronic equipment.)

After the Start Bit, the individual bits of the word of data are sent, with the Least Significant Bit (LSB) being sent first. Each bit in the transmission is transmitted for exactly the same amount of time as all of the other bits, and the receiver “looks” at the wire at approximately halfway through the period assigned to each bit to determine if the bit is a 1 or a 0. For example, if it takes two seconds to send each bit, the receiver will examine the signal to determine if it is a 1 or a 0 after one second has passed, then it will wait two seconds and then examine the value of the next bit, and so on. The sender does not know when the receiver has “looked” at the value of the bit. The sender only knows when the clock says to begin transmitting the next bit of the word. When the entire data word has been sent, the transmitter may add a Parity Bit that the transmitter generates. The Parity Bit may be used by the receiver to perform simple error checking. Then at least one Stop Bit is sent by the transmitter. When the receiver has received all of the bits in the data word, it may check for the Parity Bits (both sender and receiver must agree on whether a Parity Bit is to be used), and then the receiver looks for a Stop Bit. If the Stop Bit does not appear when it is supposed to, the UART considers the entire word to be garbled and will report a Framing Error to the host processor when the data word is read. The usual cause of a Framing Error is that the sender and receiver clocks were not running at the same speed, or that the signal was interrupted. Regardless of whether the data was received correctly or not, the UART automatically discards the Start, Parity and Stop bits. If the sender and receiver are configured identically, these bits are not passed to the host. If another word is ready for transmission, the Start Bit for the new word can be sent as soon as the Stop Bit for the previous word has been sent.

2.5 REVIEW HISTORY

Modems for personal computers that plug into a motherboard slot must also include the UART function on the card. The original 8250 UART chip shipped with the IBM personal computer had no on-chip buffering for received characters, which meant that communications software performed poorly at speeds above 9600 bits/second, especially if operating under a multitasking system or if handling interrupts from disk controllers. High-speed modems used UARTs that were compatible with the original chip but which included additional FIFO buffers, giving software additional time to respond to incoming data.

A look at the performance requirements at high bit rates shows why the 16, 32, 64 or 128 byte FIFO is a necessity. The Microsoft specification for a DOS system requires that interrupts not be disabled for more than 1 millisecond at a time. Some hard disk drives and video controllers violate this specification. 9600 bit/s will deliver a character approximately every millisecond, so a 1 byte FIFO should be sufficient at this rate on a DOS system which meets the maximum interrupt disable timing. Rates above this may receive a new character before the old one has been fetched, and thus the old character will be lost. This is referred to as an overrun error and results in one or more lost characters. With error correcting modems, any lost characters will be retransmitted, but retransmission slows the connection.

A 16 byte FIFO allows up to 16 characters to be received before the computer has to service the interrupt. This increases the maximum bit rate the computer can process reliably from 9600 to 153,000 bit/s if it has a 1 millisecond interrupt dead time. A 32 byte FIFO increases the maximum rate to over 300,000 bit/s. A second benefit to having a FIFO is that the computer only has to service about 8 to 12% as many interrupts, allowing more CPU time for updating the screen, or doing other chores. Thus the computer's responses will improve as well.

2.6 SUMMARY OF THE CHAPTER

This design uses Verilog HDL as design language to achieve the modules of UART. Using this software, Altera’s series chip to complete simulation and test, the result may be stable and reliable. The design has great flexibility, high integration with some reference value. Especially in the field of electronic design, where technology has recently become increasingly mature, this design shows great significance. This project describes the architecture of UART that support various data word length, parity selection and baud rates for serial transmission of data. Working principle of this UART has been tested using simulator, which can be implemented on Altera DE2.

The literature review describe about the history of Development of Universal Asynchronous Receiver/Transmitter for analysis to get an overview of project’s plan. The history is divided into two; previous work and present work. For previous history, the time required is 4 months starting from January till April 2013. Meanwhile, for present history, it briefly explained about the component listing and purchasing component parts, which took about a months to complete.

CHAPTER 3

METHODOLOGY

3.1 INTRODUCTION OF PROJECT’S METHODOLOGY

This chapter will discuss about the methodology of this project. The methodology chapter explains the procedure of a researcher’s academic studies. Methodology chapter are intended to be complete, detailed reports of studies with the objective that any other researcher could replicate the study exactly to determine if the same results would be obtained. This chapter will explain more details about block diagram, hardware development and software development.

3.2 BLOCK DIAGRAM

Figure 3.2a: System block diagram

3.2.1 EXPLANATION

Actually UART receives/sends data to microprocessor/microcontroller through data bus. The remaining part of signal handling of RS-232 is done by UART for example start bit, stop bit, and parity.

The following is the experimental set up for serial communication form. Data from PIC / MPLAB software will be received to RS-232 Transceiver. It modifies or converts signal into format appropriate for efficient channel of transmission. Next it will implement using Verilog HDL. Verilog is a verilfication language and hence have rich capabilities for testing. PLI (Programming Language Interface) which gives the added flexibility in testing and verification for the code written in C and then to be integrated with HDL code. Hence, it will connect to UART Peripheral connector which is physical medium through RS-232. Then it will programmed into Altera DE2 board for proof of concept.

3.3 HARDWARE AND DEVELOPMENT

3.3.1 THE ELECTRONIC PARTS

i. Max 232 interfacing

ii. RS 232 port

iii. Altera DE2 board

3.3.1.1 Max 232 Interfacing Circuit

Figure 3.3.1.1a : Max 232 Schematic Diagram

The MAX232 is an integrated circuit that converts signals from an RS-232 serial port to signals suitable for use in TTL compatible digital logic circuits. The MAX232 is a dual driver/receiver and typically converts the RX (receiver), TX (transmitter), CTS and RTS signals. The later MAX232A is backwards compatible with the original MAX232 but may operate at higher baud rates and can use smaller external capacitors – 0.1 μF in place of the 1.0 μF capacitors used with the original device. It is helpful to understand what occurs to the voltage levels. When a MAX232 IC receives a TTL level to convert, it changes a TTL Logic 0 to between +3 and +15 V, and changes TTL Logic 1 to between -3 to -15 V.

Figure 3.3.1.1b : Max 232 chip

Figure 3.3.1.1c : Max 232 functional diagram

3.3.1.2 RS232 port.

Below is the pinout of a typical standard male 9-pin RS232 connector, this connector type is also referred to as a DB9 connector.

A computer's serial COM port (DTE) is usually a male port as shown below, and any peripheral devices connect to this port usually has a female connector (DCE).

Figure 3.3.1.2a: RS232 Pin Configurations

The main features of hardware and software are as follows :

Hardware:

Interface: UART(RS232/RS422/TTL)

Data rate: 1200~115200 BPS

Power supply :3V or 6V

Receiving Current:160mA

Transmitting current:200mA(Peak current 250mA)

Standby current: 120mA

Software:

Verilog HDL, Windows.

Network Protocol: FPGAs, and GPUs as coprocessors

Working Environment Operation Temperature:-20C ~ 85C

Storage Temperature:-40C ~ 125C

3.3.1.3 Altera DE2 board

Figure 3.3.1.3a: DE2 Development and Educational Board

The Altera DE2 Development and Education board was designed by professors, for professors. It is an ideal vehicle for learning about digital logic, computer organization, and FPGAs. Featuring an Altera Cyclone II 2C35 FPGA, the DE2 board is designed for university and college laboratory use. It is suitable for a wide range of exercises in courses on digital logic and computer organization, from simple tasks that illustrate fundamental concepts to advanced designs. Altera DE2 Development board as follows:

Feature	Description
FPGA	· Cyclone II EP2C35F672C6 with EPCS16 16-Mbit serial configuration device
I/O Interfaces	· Built-in USB-Blaster for FPGA configuration · Line In/Out, Microphone In (24-bit Audio CODEC) · Video Out (VGA 10-bit DAC) · Video In (NTSC/PAL/Multi-format) · RS232 · Infrared port · PS/2 mouse or keyboard port · 10/100 Ethernet · USB 2.0 (type A and type B) · Expansion headers (two 40-pin headers)
Memory	· 8 MB SDRAM, 512 KB SRAM, 4 MB Flash · SD memory card slot
Displays	· Eight 7-segment displays · 16 x 2 LCD display
Switches and LEDs	· 18 toggle switches · 18 red LEDs · 9 green LEDs · Four debounced pushbutton switches
Clocks	· 50 MHz clock · 27 MHz clock · External SMA clock input

3.4 SOFTWARE AND DEVELOPMENT

This chapter will discuss the information and reference about the software development for each circuit part of this project. In order to develop the project, the strategy must be thoroughly planned before starting to build it.

3.4.1 Verilog HDL Software

Figure 3.4.1a: Verilog HDL Lecture Note

3.4.2 Data Encoding

When no data transmitted D remains high. To signal a start of new transmission D goes low for 1 bit period, which is known as “Start bit”. After the Start Bit, the individual bits of data are sent. Each bit in the transmission is transmitted for exactly the same amount of time as all of the other bits. After transmission of entire data has been sent then D again goes to high, the last bit known as “Stop bit”. Transmission of next data can begin any time after that.In our project we have “even parity” bit for parity check.

Test Bench (Receiver and Transmitter): Receiver and Transmitter are working independently.

Figure 3.4.2a: Verilog HDL Software Interface

3.4.3 Receiver

Receiver takes data serially in RxD pin, and provides the parallel to the Data out pin. UART receiver consists of RDR (Received Data Reg.) and controller. When the UART detects start bit receiver reads and shifts 8 data bits serially into a temporary register. When 8 data bits has been received and parity check passes then after stop bit has been received controller transfers data from temporary register to RDR and received signal goes high.

Receiver VHDL Model

libraryIEEE;

useIEEE.STD_LOGIC_1164.ALL;

useIEEE.STD_LOGIC_ARITH.ALL;

useIEEE.STD_LOGIC_UNSIGNED.ALL;

entityuart_receiveris

Port(clk:inSTD_LOGIC;

rx:instd_logic;

reset :inSTD_LOGIC;

baud_tick:inSTD_LOGIC;

data_out:outSTD_LOGIC_VECTOR(7downto0);

received :outSTD_LOGIC;

count1:outstd_logic_vector(3downto0);

count2:outstd_logic_vector(2downto0)

);

enduart_receiver;

architecture Behavioral ofuart_receiveris

type state is(idle,startbit,databits,paritybit,stopbit);

signalstate_reg,next_state_reg: state;

signalcounter,next_count:std_logic_vector(3downto0);

signaldata_count,data_next_count:std_logic_vector(2downto0);

signalrec,next_rec:std_logic_vector(7downto0):="00000000";

signalparity:std_logic;

begin

process(clk, reset)

begin

if(reset='1')

then

state_reg<=idle;

counter<=(others=>'0');

data_count<=(others=>'0');

elsif(rising_edge(clk)AND reset='0')

then

state_reg<=next_state_reg;

counter<=next_count;

data_count<=data_next_count;

rec<=next_rec;

endif;

endprocess;

state_decode:process(state_reg,rx,counter,baud_tick)

begin

if(state_reg=idle)then

next_state_reg<=state_reg;

data_next_count<=data_count;

received<='0';

next_count<=counter;

next_rec<=rec;

if(rx= '0')then

next_state_reg<=startbit;

next_count<=(others=>'0');

next_rec<="00000000";

endif;

elsif(rising_edge(baud_tick))then

next_state_reg<=state_reg;

data_next_count<=data_count;

received<='0';

next_count<=counter;

next_rec<=rec;

if(state_reg=startbit)then

if(('0'&counter)=7)

then

next_state_reg<=databits;

next_count<=(others=>'0');

data_next_count<=(others=>'0');

else

next_count<=counter+1;

endif;

elsif(state_reg=databits)then

if(('0'&counter)=15)then

next_count<=(others=>'0');

next_rec<=(rx& rec(7downto1));

if(('0'&data_count)=7)then

next_state_reg<=paritybit;

else

data_next_count<=data_count+1;

endif;

else

next_count<=counter+1;

endif;

elsif(state_reg=paritybit)then

if(('0'&counter)=15)then

next_count<=(others=>'0');

next_state_reg<=stopbit;

if(not(parity=rx))then

next_rec<="01000101";

endif;

else

next_count<=counter+1;

endif;

elsif(state_reg=stopbit)then

if(('0'&counter)=10)

then

received<='1';

next_count<=counter+1;

elsif(('0'&counter)=15)then

next_state_reg<=idle;

else

next_count<=counter+1;

endif;

endprocess;

parity<=rec(7)xor rec(6)xor rec(5)xor rec(4)xor rec(3)xor rec(2)xor rec(1)xor rec(0);

data_out<=rec;

count1<=counter;

count2<=data_count;

end Behavioral;

3.4.4 Transmitter

Transmitter takes parallel data and sends it serially on the TxD pin.The transmitter consists of TDR (Transmit Data Register),TSR (Transmit Shift Register) and controller. As load signal goes high transmitter transfers data from TDR to TSR and outputs start bit “0” to the TxD pin then shifts TSR right eight times to transmit 8 bits. When eight data bits transmitted ,transmitter sends parity bit and finally outputs stop bit”1” to the TxDpin and signal “transmitted” goes high.

Transmitter VHDL Model

libraryIEEE;

useIEEE.STD_LOGIC_1164.ALL;

useIEEE.STD_LOGIC_ARITH.ALL;

useIEEE.STD_LOGIC_UNSIGNED.ALL;

entity transmitter is

port(

clk:inSTD_LOGIC;

reset :inSTD_LOGIC;

load :inSTD_LOGIC;

baud_tick:inSTD_LOGIC;

din :instd_logic_vector(7downto0);

transmitted :outSTD_LOGIC;

TxD:outSTD_LOGIC;

count1:outstd_logic_vector(3downto0);

count2:outstd_logic_vector(2downto0)

);

end transmitter;

architecture archof transmitter is

type state is(idle,start,data,parity_s,stop);

signalstate_reg,state_next:state;

signalcount,count_next:std_logic_vector(3downto0);

signaldcount,dcount_next:std_logic_vector(2downto0);

signal TSR ,TSR_next:std_logic_vector(7downto0):="00000000";

signaltx,tx_next:std_logic;

signalparity:std_logic;

begin

process(clk, reset)

begin

if(reset='1')

then

state_reg<=idle;

count<=(others=>'0');

dcount<=(others=>'0');

TSR<=(others=>'0');

tx<='1';

elsif(rising_edge(clk)AND reset='0')

then

state_reg<=state_next;

count<=count_next;

dcount<=dcount_next;

TSR<=TSR_next;

tx<=tx_next;

endif;

endprocess;

state_decode:process(state_reg,baud_tick,tx,load,din)

begin

if(state_reg=idle)

then

state_next<=state_reg;

count_next<=count;

dcount_next<=dcount;

TSR_next<=TSR;

transmitted<='0';

tx_next<='1';

if(load = '1')

then

state_next<=start;

count_next<=(others=>'0');

TSR_next<=din;

endif;

elsif(rising_edge(baud_tick))

then

state_next<=state_reg;

count_next<=count;

dcount_next<=dcount;

TSR_next<=TSR;

tx_next<=tx;

transmitted<='0';

if(state_reg= start)

then

tx_next<=tx;

if(('0'&count)=15)

then

state_next<= data;

count_next<=(others=>'0');

dcount_next<=(others=>'0');

else

count_next<=count+1;

endif;

if(state_reg= data)

then

tx_next<=TSR(0);

if(count=15)

then

count_next<=(others=>'0');

TSR_next<= '0' &TSR(7downto1);

if(dcount=7)

then

state_next<=parity_s;

else

dcount_next<=dcount+1;

endif;

else

count_next<= count +1;

endif;

if(state_reg=parity_s)

then

tx_next<=parity;

if(count=15)

then

count_next<=(others=>'0');

state_next<= stop;

else

count_next<= count +1;

endif;

if(state_reg= stop)

then

tx_next<='1';

if(count=10)

then

transmitted<='1';

count_next<= count +1

elsif(count=15)

then

state_next<= idle;

else

count_next<= count +1;

endif;

endprocess;

count1 <=(count);

count2 <=dcount;

parity<=din(7)xor din(6)xor din(5)xor din(4)xor din(3)xor din(2)xordin(1)xor din(0);

TxD<=tx;

end arch;

3.5 SUMMARY OF THE CHAPTER

As conclusion, might say the overall of the methodology had been discussed by sharing the same ideas and combining the knowledge of the software and hardware development. The hardware development is the most important element that inclusive of block diagram, hardware prototype and their description. The block diagram is explained about basic concept operation of Development of Universal Asynchronous Receiver/ Transmitter using Verilog HDL.

For the software development, I am using Verilog HDL software to communicate between the RS232 port with Altera DE2 board. This software is one of important as the machine instructions or source code that responsible to perform the desired task as required.

Last but not least, this chapter is very useful as the guidance and it is also helpful to overview the whole project that will be implemented in the future. Therefore it is very significant to discover the new application design.

CHAPTER 4

RESULT AND ANALYSIS

4.1 INTRODUCTION

This chapter will explain the expected result of Development of Universal Asynchronous Receiver / Transmitter Interface using Verilog HDL.

Transmitting and receiving UARTs must be set for the same bit speed, character length, parity, and stop bits for proper operation. The receiving UART may detect some mismatched settings and set a framing error flag bit for the host system; in exceptional cases the receiving UART will produce an erratic stream of mutilated characters and transfer them to the host system.

Typical serial ports used with personal computers connected to modems use eight data bits, no parity, and one stop bit; for this configuration the number of ASCII characters per second equals the bit rate divided by 10.

Some very low-cost home computers or embedded systems dispensed with a UART and used the CPU to sample the state of an input port or directly manipulate an output port for data transmission. While very CPU-intensive, since the CPU timing was critical, these schemes avoided the purchase of a UART chip. The technique was known as a banging serial port.

4.1.1 The Electronic Circuit Analysis and Theory

Figure below shows that the electronic circuit of Universal Asynchronous Receiver / Transmitter using PIC 16F877A. The circuit contains of:

1. Pull down resistor

2. Oscillator

3. UART interface driver

4. PIC 16F877A chip

5. 4X3 push button keypad

The function of pull down resistor is to pull current into the circuit and supply voltage to the PIC 16F877A to make sure the circuit is on. Oscillator provides a good contribution of frequency to make sure the noise in the circuit is at the minimum level. The ideal frequency for this circuit is around 12MHz. UART interface driver is an important component in this final year project. I need to calibrate the driver so that it could be interface to Altera DE2 board. PIC 16F877A chip is a reader for MPLAB IDE program code (microcontroller) whether I write my program have no error and can run the program. While 4X3 push button keypad is to verify and show that what I push at this keypad will appear at the Altera DE2 board.

Figure 4.1.1a : Electronic circuit of Universal Asynchronous Receiver / Transmitter using PIC 16F877A

4.2 THE EXPECTED OUTPUT

Below is the expected output for this final year project. The expected output including RTL viewer, State Machine viewer and last but not least the most important UART Verilog HDL code.

Figure 4.2a: RTL Viewer

From the RTL viewer we can see reset, clock and start logic circuit, adder, or gates, bit counter, shift register, baud rate counter and D flip flop. The systems has been used Quartus II 2011 as simulation software. It was very important to develop and test such design before a physical prototype is constructed.

Figure 4.2b : State Machine Viewer

Figure 4.2c : UART Verilog Code

This project has extremely difficult programming code to interface it by using 2 different of programming software. However, I am manage to success to run the program using Verilog HDL.

4.3 THE EXPECTED RESULT

The figure below show what is the expected result from this Final Year Project. This expected result including Successful compiling using MPLAB IDE software, keypad compiling using MPLAB IDE software, RS 232 compiling using MPLAB IDE software, UART main compiling using MPLAB IDE software and UART compiling using MPLAB IDE software.

Figure 4.3a : Successful compiling using MPLAB IDE software

Figure 4.3b : Keypad compiling using MPLAB IDE software

This part of coding I use switch_case method to perform the program. I have to design the keypad exactly as the Electronic circuit of Universal Asynchronous Receiver / Transmitter using PIC 16F877A to make sure there is no error while running this program.

Figure 4.3c : RS 232 compiling using MPLAB IDE software

The program in figure above shows how I am able to communicate between MPLAB IDE software to RS 232 port. I have configured all the pins in RS232 port with the software. For this program I am using while_if method.

Figure 4.3d : UART main compiling using MPLAB IDE software

In this figure shows how I need to combine or interface the program of MPLAB IDE software by using PIC 16F877A to UART that using Verilog HDL software. Verilog HDL is a case sensitive and I must declare all the details in the program.

Figure 4.3e : UART compiling using MPLAB IDE software

For this figure it is shown the codings that I have to synchronize with UART peripheral device to perform the output at the Altera DE2 board. The codings must be complete and no error so that the output of this program can be compile with the Verilog HDL program to perform the output of this final year project.

4.4 SUMMARY OF THE CHAPTER

In this chapter, I have explained The Electronic Circuit Analysis and Theory, The Expected Output and The Expected Result. I also provide the codings from both software from the Verilog HDL and MPLAB IDE. Unfortunately, the Altera DE2 board could not interface with this programming. There were a few problems occur while doing software and hardware on this project. In order to solve this problems, the research and discussion were made with supervisor and also some references from journal report.

CHAPTER 5

CONCLUSION AND RECOMMENDATION

5.1 CONCLUSION

This review has introduced the technique of Universal Asynchronous Receiver/ Transmitter and has demonstrated its great potential for use in a wide range of communication. A main focus has been the assessment of the data transmission system. In recent years there has been interesting the technique, and driven by the demand for low cost, simple and portable technology forth settings, the availability of low cost and small semiconductor components, and the advancement of computer analysis techniques. I can conclude from this project that I am trying my best to achieve my objective. First, I success todesign a serial asynchronous receiver and transmitter communication with standard I/O serial devices. Then, I also success to achieve my second objective, that is design a UART that can be prototyping Altera DE2, then testing and debugging the prototype in system. At the same time, I also cananalyze the features of UART technology and make comparison with other existing UART technology. In addition, I also implement the asynchronous receiver-transmitter in Altera DE2 board to achieve fast prototyping and design verification. Lastly, I already know how to use and capable using UART in Verilog HDL.Here, I already achieve our entire objective. This design uses Verilog HDL as design language to achieve the modules of UART. Using this software, Altera’s series chip to complete simulation and test, the result may be stable and reliable. The design has great flexibility, high integration with some reference value. Especially in the field of electronic design, where technology has recently become increasingly mature, this design shows great significance. This project describes the architecture of UART that support various data word length, parity selection and baud rates for serial transmission of data. Working principle of this UART has been tested using simulator, which can be implemented on Altera DE2.

Unfortunately, this project is not successfully developed. The Altera DE2 Board is still not been fully interface with the Universal Asynchronous Receiver / Transmitter. Sometimes the resistor tolerance also gives effect to the circuit. When supply the voltage, make sure it will enhance the circuit to run, not to ruin the circuit. That is why the datasheet of every component is very important to know the voltage and current limit.

5.2 RECOMMENDATION

Few recommendations to upgrade the system of Universal Asynchronous Receiver / Transmitter have been thought throughout this two semester. First, try to use FTDI chip to interface the Altera DE2 Board and UART. FTDI chip carries the RS232 handshake signaling with the main-stream data exchange over the same USB bulk endpoint; bulk OUT EP: TxD - RTS, DTR, bulk IN EP: RxD - CTS, DSR, DCD, RI. Then, at least, the order of the signaling is preserved but the detailed timing is not guaranteed. For example, when we handle serial lines on a PC application as follows, PC sets RTS, 3 ms delay and PC sends data over TxD. On the RS232 side of the chip, we will observe this sequence RTS change, 0 ms or more delay and TxD starts. SiLabs and Prolific chip carries the handshake signaling over the default endpoint, instead of the bulk one. The timing between different endpoints is not guaranteed, even for the order. In above example, we may see this result on the RS232 side such as TxD starts, some ms delay and RTS change. FTDI is better, when the handshake signaling is applied. But when the application makes the detailed timing on the PC app, it may still fail even on FTDI chip. This argument is extended to all USB application. When we want to guarantee the timing over USB, there is no other way than applying the USB frame (or microframe) number to synchronize the host application and the device. The last one is, since this project is about to do research and need to collect data, I would like to suggest to the university to extend the period of doing the final project.

6.0 REFERRENCES

[1] S. Mackay, E. Wright, D. Reynders, J. Park, Practical Industrial Data Networks:Design, Installation and Troubleshooting, Newnes, 2004ISBN 07506 5807X, pages 41-42

[2] Wilson, Michael R. (January 2000). "TIA/EIA-422-B Overview". Application Note 1031. National Semiconductor. Retrieved 28 July 2011

[3] Joseph Cavanagh, Digital Design and Verilog HDL Fundamentals, Published 17th June 2008 by CRC Press

[4] D. Michael Miller; Mitchell A. Thornton (2008). Multiple Valued Logic: Concepts and Representations. Synthesis lectures on digital circuits and systems. Morgan & Claypool Publishers. ISBN 978-1-59829-190-2.

[5] JanickBergerdon, "Writing Test benches: Functional Verification of HDL Models", 2000.

[6] http://www.altera.com.my/education/univ/materials/boards/de2/unv-de2-board.html

[7] http://www.verilogcourseteam.com/vlsiproject3

[8] I. M. Braverman, “The Cutaneous Microcirculation”, J Investig Dermatol Symp Proc. ,vol.5, pp.3-9,2000

[9] J. D. Briers, Laser Doppler and time-varying speckle: reconciliation, J. Opt. Soc. Am. A 13 (1996), 345-50

[10] Lecture Note Digital Design S1P 2013, Sir Suhaimi Bahisham bin Yusof, Universiti Kuala Lumpur British Malaysian Institute.

...FINAL YEAR PROJECT...©

Tuesday, January 14, 2014

Final Year Project Semester 2 Full Report

2.2.3 Wireless Temperature and Humadity Sensor