Serial Communication With LPC2148
by embeddedbymedhavi in Circuits > Microcontrollers
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Serial Communication With LPC2148

BASICS OF SERIAL COMMUNICATION:·
- Serial communication uses single data line making it much cheaper·
- enables two computers in different cities to communicate over the telephone·
- Byte of data must be converted to serial bits using a parallel-in-serial-out shift register and transmitted over a single data line·
- Receiving end there must be a serial-in-parallel-out shift register·
- If transferred on the telephone line, it must be converted to audio tones by modem·
- For short distance the signal can be transferred using wire·
- how PC keyboards transfer data to the motherboard·
- 2 methods, asynchronous and synchronous·
- synchronous method transfers a block of data (characters) at a time·
- asynchronous method transfers a single byte at a time·
- Uses special IC chips called UART (universal asynchronous receiver-transmitter) and USART (universal synchronous asynchronous receiver-transmitter)
Data Transfer Rate

- rate of data transfer bps (bits per second)
- widely used terminology for bps is baud rate ·
- baud and bps rates are not necessarily equal ·
- baud rate is defined as the number of signal changes per second
RS232 Standards


- most widely used serial I/O interfacing standard
- input and output voltage levels are not TTL compatible ·
- 1 bit is represented by -3 to -25 V ·
- 0 bit is +3 to +25 V ·
- -3 to +3 is undefined ·
- to connect RS232 to a microcontroller system must use voltage converters such as MAX232 to convert the TTL logic levels to the RS232 voltage levels, and vice versa ·
- MAX232 IC chips are commonly referred to as line drivers
Data Communication Classification

- DTE (data terminal equipment)·
- DCE (data communication equipment)·
- DTE - terminals and computers that send and receive data·
- DCE - communication equipment responsible for transferring the data·
- Simplest connection between a PC and microcontroller requires a minimum of three pins, TxD, RxD, and ground
ARM SERIAL PORT PROGRAMMING IN C:
- Baud rate in the LPC2148:·
- serial communications of the LPC2148 with the COM port of the PC·
- must make sure that the baud rate of the LPC2148 system matches the baud rate of the PC's COM port·
- can use Windows HyperTerminal program
Write a Program to Transfer Letter 'A' Serially at 9600 Baud, Continuously.

Simulation of transfer letter "A" is given in above.
C Code of transfer letter "A" :
Downloads
Write a Program to Transfer Letter "WELCOME TO ALL" and "GOD BLESS YOU " Serially at 9600 Baud, Continuously.

Simulation of transfer letter "WELCOME TO ALL" is given in above.
C Code of transfer letter "WELCOME TO ALL" :
Downloads
Program the LPC2148 to Receive Bytes of Data Serially and Put Them on LCD. Set the Baud Rate at 9600, 8-bit Data, and 1 Stop Bit.

Simulation of receive is given in above.
C Code of receive :
Downloads
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