Use RS485

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:

RS485-connection

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.