User`s manual

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User’s Manual 53

4.3.3 Serial Communication

The following sample programs are found in the RS232 subdirectory in SAMPLES\OP7200.

• PUTS.C—This program transmits and then

receives an ASCII string on Serial Ports C and

D. The serial data received are displayed in the

STDIO window.

To set up the OP7200, you will need to tie

TxC and RxD together on the screw-terminal

header at J10, and you will also tie TxD and

RxC together as shown in the diagram.

• RELAYCHR.C—This program echoes charac-

ters to or from a serial utility such as Hyper-

Terminal or Tera Term.

To set up the OP7200, you will need to tie

TxC and RxD together on the screw-terminal

header at J10.

Set up HyperTerminal or Tera Term as follows: 19200 bps, 8 data bits, no parity, 1 stop

bit, and no flow control. Here are a few additional settings if you are using Tera Term.

X Disable Local Echo in the Terminal setup

X Enable the receive and line feed options (CR + LF) under New line in the Terminal setup

Now when you type characters in the HyperTerminal or Tera Term window, they will

appear in the window because they are being echoed back by the sample program.

Two sample programs, MASTER.C and SLAVE.C, are available in the RS485 subdirectory

in SAMPLES\OP7200 to illustrate RS-485 master/slave communication. To run these

sample programs, you will need a second Rabbit-based system with RS-485—another

Rabbit single-board computer or OP7200 may be used as long as you use the master or

slave sample program associated with that board.

The RS-485 connections between the slave and master devices are as follows.

• RS485+ to RS485+

• RS485– to RS485–

• GND to GND

Then connect your PC COM port to screw-terminal

header J10 as follows.

X PC Tx to RxC on J10

X PC Rx to TxD on J10

X PC GND to GND on J10

J10

GND

+485

485

RXD/CTS

TXD/RTS

RXC

TXC

/RST

IN15

IN14

IN13

IN12

J10

GND