Edge 2 has one RS485 connector.
Connecting hardware
Port the USB to RS485 converter to the PC, and connect the cable to the Edge 2 RS485 connector. Refer to the following wire sequence connection diagram:
Testing RS485
Open the PC serial port
Taking macOS as an example, the USB to RS485 converter node tty.usbserial-14310 exists in the system, and the command to open it through the picocom tool is as follows:
$ picocom -b 9600 /dev/tty.usbserial-14310
The USB to UART converter node exists in the Ubuntu in the form of /dev/ttyUSB[1, 2, 3.....].
The USB to UART converter node exists in the Windows in the form of COM[1、2、3....].
For more details, please refer to the Serial Debugging.
Sending data from Edge 2
The Edge 2 UART5 device file is /dev/ttyS4. Run the following commands on Edge 2:
echo "edge2 RS485 test..." > /dev/ttyS4
The PC serial terminal (picocom) should receive the string “edge2 RS485 test…”.
Receiving data by Edge 2
Run the following command on Edge 2.
cat /dev/ttyS4
Send a string, e.g. “edge2 UART5 test…”, using the PC serial terminal (picocom) to test the connection. Edge 2 should see the same string.
Configuring RS485
[Note]: The Android / Debian released by Mixtile already enabled the RS485 function in the kernel, so you could just ignore the below instruction. If you plan to compile your Andorid / Debian system, please remember to configure RS485 as below.
The Edge 2 RS485 connector corresponds to UART4. To use RS485, you need to enable UART4 in the kernel.
The following files involved in the kernel:
kernel/arch/arm64/boot/dts/rockchip/mixtile-edge2.dts
To enable UART4:
&uart4 {
status = "okay";
pinctrl-0 = <&uart4m1_xfer>;
};
To compile the kernel, please refer to the Compile kernel chapter for more details.
To burn boot.img, please refer to Update Firmware chapter for more details.