MX9 UART

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DART-MX95 UART

UART Overview

UART Overview - DART-MX95

The DART-MX95 expose up to eight LPUART interfaces, some of which are multiplexed with other peripherals.

Serial Port Device Node Device Tree DART-MX95 / DT8MCustomBoard
UART1 /dev/ttyLP0 lpuart1 DT8MCustomboard serial console
UART2 /dev/ttyLP1 lpuart2 Disabled by default, see datasheet
UART3 /dev/ttyLP2 lpuart3 Disabled by default, used as Cortex-M7 console, connected to DT8MCustomboard J12.11 and J12.13
UART4 /dev/ttyLP3 lpuart4 Disabled by default, see datasheet
UART5 /dev/ttyLP4 lpuart5 1.8V Signal level, used on SOM for Bluetooth interface and can be accessible only if Bluetooth is disabled.[1]
UART6 /dev/ttyLP5 lpuart6 Disabled by default, see datasheet
UART7 /dev/ttyLP6 lpuart7 Disabled by default, see datasheet
UART8 /dev/ttyLP7 lpuart8 Connected to DT8MCustomboard J12.4 and J12.6

Disabling Bluetooth / Enabling UART5 (/dev/ttyLP4)

UART4/ttyLP4 is used by the Bluetooth on the SOM. To use it on the carrier, Bluetooth must be disabled on the SOM.

First, disable variscite-bt by running:

# systemctl stop variscite-bt; systemctl stop variscite-ot
# systemctl disable variscite-bt; systemctl disable variscite-ot

Then, disable bluetooth in the device tree imx95-var-dart.dtsi:

&lpuart5 {
   ...
	bluetooth {
		compatible = "nxp,88w8987-bt";
		status = "disabled";
	};
   ...
};

Testing UART8

The following demonstrates how to test UART8 on the DART-MX95 DT8MCustomboard following the table above.

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

# stty -F /dev/ttyLP7 -echo -onlcr 115200
# cat /dev/ttyLP7 &
# echo hello > /dev/ttyLP7

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