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In this article, 3 example codes are provided to demonstrate the UART Communication. RS232 interface using Max3232 Driver IC with Spartan3 FPGA Image Processing Boardįig 6: Schematic diagram of FPGA and MAX 3232 UART Placement in Spartan3 FPGA Image Processing Board RS 232 connector has only 9 pins, even though the only 3 pins are enough to make a transmission between PC and FPGA such as RD,TD and GND. Here we use only female to female connector. RS 232 connector is used to establish connection between Spartan3 FPGA Image Processing Board and PC. The transmission delay for each bit 104.16 μs which is constant till the end of communication. Each bit has a fixed time duration while transmission.

The transmission rate is measured by bits per second. Note: The parity bit is not necessary which is optional. The last bit is stop bit which must be ‘1’. The speed of transmission is fixed which is measured by baud rate. If odd parity is used, the number of bit must be odd. If even parity is used, the number of bit must be even. The parity bit is either 0 or 1 which is depending on the number of 1’s present in transmission. The 10th bit is a parity bit which is used to identify error in the communication. The LSB bit of data goes as first bit continue it sent other 7 bits. Here the ‘0’ bit represent as start bit which is initiated the serial communication. The wave form showed the protocol of the UART. The data communication of UART is made by 11 bit blocks. It consists of 2 channel transmitter and Receiver. In order to communicate between FPGA and PC with different voltage level, MAX3232 Driver IC is required. On PC Side RS232 Port voltage range from -15v to +15v. Serial data communicate on FPGA side range in 0 to 3.3v. Serial Communication consist of 2 lines Transmitter and Receiver pin. For example Spartan3 FPGA Image Processing Boardtransmit data at the baud rate of 9600 and at the receiving end PC need to be set with same baud rate using HyperTerminal or TeraTerminal. Transmitter and receiver need to be maintained in the baud rate. It includes Start bit, Data byte, Parity bit and Stop bit. Baud rate describes the total number of bit sent through serial communication.

In the UART communication data transmission speed is measured by Baud Rate. As the entire processes require no clock input from source hence it is termed as asynchronous communication. UART transmit bytes of data sequentially one bit at a time from source and receive the byte of data at the destination by decoding sequential data with control bits. The function of UART is conversion parallel data (8 bit) to serial data. UART Stands for Universal Asynchronous Transmitter Receiver.