Use UART

Edge 2 has two UART interfaces, UART3 and UART5.

Connecting hardware

Port the USB to UART converter to the PC, and connect the cable to the edge2 UART3/UART5 connector. Refer to the following wire sequence connection diagram:

uart-connection

Configuring UART

To use Edge 2 UART3 and UART5, you need to enable UART3 and UART5 in the dts of the kernel.

The following file is involved in the kernel:

kernel/arch/arm64/boot/dts/rockchip/mixtile-edge2.dts

To enable UART3 and UART5:

&uart3 {
    status = "okay";
    pinctrl-0 = <&uart3m1_xfer>;
};

&uart5 {
    status = "okay";
    pinctrl-0 = <&uart5m1_xfer>;
};

To compile the kernel, please refer to the Compile kernel chapter for details.

To burn boot.img, please refer to Update Firmware chapter for details.

Testing UART

Open the PC serial port

Taking macOS as an example, the USB to UART converter node tty.usbserial-AQ01C9CC% exists in the system, and the command to open it through the picocom tool is as follows:

$ picocom -b 9600 /dev/tty.usbserial-AQ01C9CC% 

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/ttyS5. Run the following commands on Edge 2:

echo "edge2 UART5 test..." > /dev/ttyS5

The PC serial terminal (picocom) should receive the string "edge2 UART5 test...".

Receiving data with Edge 2

Run the following command on edge2:

cat /dev/ttyS5

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.

Note: UART3 usage is the same as UART5.