StarSBC-6ULL RS232 example
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StarSBC-6ULL RS232 example
This tutorial shows how to send and receive data using RS232 interface on StarSBC-6ULL with communication extension board. The default Yocto image build according the tutorial VisionSOM_imx-meta-somlabs-hardknott contains all required software tools.
Loop test
The extension board has two RS232 interfaces available so they may be connected to perform the test in a loop. All signals are available on the J101 and J201 connectors. They should be connected according to the following table:
| RS232-1 signal | RS232-2 signal |
|---|---|
| RS232-1 TXD (J101 pin 3) | RS232-2 RXD (J201 pin 8) |
| RS232-1 RXD (J101 pin 4) | RS232-2 TXD (J201 pin 7) |
| RS232-1 CTS (J101 pin 1) | RS232-2 RTS (J201 pin 10) |
| RS232-1 RTS (J101 pin 2) | RS232-2 CTS (J201 pin 9) |
Both interfaces are already defined in the default module device-tree and are recognized as /dev/ttymxc2 and /dev/ttymxc6 devices. The device files may be used directly for reading and writing and the bitrate may be set using the stty tool:
root@starsbc-6ull:~# stty -F /dev/ttymxc2 9600 crtscts root@starsbc-6ull:~# stty -F /dev/ttymxc6 9600 crtscts root@starsbc-6ull:~# cat /dev/ttymxc2 & [1] 465 root@starsbc-6ull:~# echo "123" > /dev/ttymxc6 123
