UART¶

UART Overview¶

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

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";
    };
   ...
};

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.