DART-MX8M UART

DART-MX8M - UART

DART-MX8M UART Overview

All 4 UARTs on DART-MX8M are enabled by default.
UART1 is connected to debug console, UART2 and UART3 are connected to header J12 on DART-MX8M carrier board, UART4 is connected to Bluetooth module.
On DART-MX8M SoMs without WIFI/BT module UART4 is also connected to J12 header.
See carrier board datasheet https://www.variscite.com/wp-content/uploads/2018/04/VAR-DT8MCustomBoard-Datasheet.pdf for the exact pinout.
Only UART4 has RTS and CTS lines.

UART naming under Linux

The Linux devices corresponding to UART1 - UART4 are /dev/ttymxc0 - /dev/ttymxc3 respectively.

Testing UART2

Short J12.4 and J12.6 pins and run the following commands:

stty -F /dev/ttymxc1 -echo -onlcr 115200
cat /dev/ttymxc1 &
echo hello > /dev/ttymxc1

Each time you run echo command the "hello" string should appear on the terminal.

Testing UART3

Short J12.11 and J12.13 pins and run the following commands:

stty -F /dev/ttymxc2 -echo -onlcr 115200
cat /dev/ttymxc2 &
echo hello > /dev/ttymxc2

Each time you run echo command the "hello" string should appear on the terminal.

Disabling UART2

To disable UART2 edit arch/arm64/boot/dts/variscite/imx8m-vart-dart-common.dsti under kernel source directory and modify

&uart2 {
        ...
        status = "okay";
};

to

&uart2 {
        ...
        status = "disabled";
};