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STR71x UART COMMUNICATION WITH A PC USING RS232

3 SERIAL COMMUNICATION BETWEEN STR71X AND PC VIA RS232

The software used for this application is the UART driver. It is up to you to adapt it to your spe-

cific application.

3.1 GENERAL DESCRIPTION

In this application, an STR71x is connected to a PC. The communication is performed using

the Windows “HyperTerminal” application.

Characters are sent by the PC in ASCII code to the STR71x. Each time 4 characters are re-

ceived by the STR71x, they are sent back to the PC and can be read on its screen.

The software is a polling serial communication between an STR71x and a PC via RS232 using

the UART0. The communication works at 9600bps, 8-bit word length without parity and has 1

stop bit.

The first part of the program performs the initialization of the STR71x core and UART0 periph-

eral. The program sends the content of a 4-byte buffer to the PC. The initialized value of the

buffer is “test” in ASCII code. When the 4 characters are sent, the program enters reception

mode. In reception mode, the software waits for the user to send 4 ASCII characters from the

PC. Each character is put in the buffer until the fourth is received. Then it goes back to trans-

mission mode which will send the new contents of the buffer and so on.

As the STR71x sends the same characters as received, it is very easy to check if the commu-

nication is correct. Note that this program does not manage communication errors.

3.2 HARDWARE

The STR71x UART peripheral cannot be directly connected to a PC, as it uses the RS232 pro-

tocol. The conversion between UART and RS232 can be done using a ST3232. An overview

schematic is presented below (Figure 3).