DART-MX8M UART

DART-MX8M UART

UART Overview

On DART-MX8M all 4 UARTs are enabled by default.
UART1 is connected to debug console.
UART2 and UART3 are connected to J12 header on VAR-DT8MCustomBoard.
UART4 is connected to Bluetooth module.
On DART-MX8M SoMs without WIFI/BT module UART4 is also connected to J12 header.
See the carrier board datasheet 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 on DART-MX8M

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

For each time you run this echo command the "hello" string should appear on the terminal.

Testing UART3 on DART-MX8M

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

For each invocation of echo command the "hello" string should appear on the terminal.

Disabling UART2

To disable UART2 on DART-MX8M edit arch/arm64/boot/dts/freescale/fsl-imx8mq-var-dart-common.dtsi under kernel source directory and modify

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

to

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

Other UARTs can be disabled in the same manner.