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

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

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

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