MX9 UART

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VAR-SOM-MX93 UART

VAR-SOM-MX93 UART Overview

The VAR-SOM-MX93 exposes up to seven LPUART interfaces, some of which are multiplexed with other peripherals.

Serial Port	Device Node	Device Tree	Note
UART0	/dev/ttyLP0	lpuart1	Connected to Symphony board serial console
UART2	/dev/ttyLP2	lpuart3	Disabled by default, see datasheet
UART3	/dev/ttyLP3	lpuart4	Disabled by default, see datasheet
UART4	/dev/ttyLP4	lpuart5	1.8V Signal level, used on SOM for Bluetooth interface and can be accessible only if the variscite-bt Systemd service is disabled or SOM without "WBD" and "WB"
UART5	/dev/ttyLP5	lpuart6	Connected to Symphony board J18.7 and J18.9
UART6	/dev/ttyLP6	lpuart7	Connected to Symphony board J18.3 and J18.5
UART7	/dev/ttyLP7	lpuart8	Disabled by default, see datasheet

Testing UART5

Short J18.7 and J18.9 pins and run the following commands:

# stty -F /dev/ttyLP5 -echo -onlcr 115200
# cat /dev/ttyLP5 &
# echo hello > /dev/ttyLP5

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

Testing UART6

Short J18.3 and J18.5 pins and run the following commands:

# stty -F /dev/ttyLP6 -echo -onlcr 115200
# cat /dev/ttyLP6 &
# echo hello > /dev/ttyLP6

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

Disabling UART5

To disable UART5 edit arch/arm64/boot/dts/freescale/imx93-var-som-symphony.dts under kernel source directory and modify

&lpuart6 {
        ...
        status = "okay";
};

to

&lpuart6 {
        ...
        status = "disabled";
};

Other UARTs can be disabled in a similar manner by referencing the table above.