MX8 UART
VAR-SOM-MX8X UART Overview
On VAR-SOM-MX8X up to 4 UARTS can be used.
All 4 UARTs are enabled by default.
UART3 is used as for debug console, UART0, UART1 and UART2 are connected to J18 header on Symphony-Board.
UART0 is connected to Bluetooth module on SOM, it can be used on J18 only when BT is disabled.
Only UART0, UART1 have RTS and CTS lines.
Inspect the carrier board datasheet or schematics for the exact pinout.
UART naming under Linux
The Linux devices corresponding to UART0 - UART4 are /dev/ttyLP0 - /dev/ttyLP4 respectively.
Testing UART1
Short J18.3 and J18.5 pins and run the following commands:
# stty -F /dev/ttyLP1 -echo -onlcr 115200 # cat /dev/ttyLP1 & # echo hello > /dev/ttyLP1
For each invocation of echo command the "hello" string should appear on the terminal.
Testing UART2
Short J18.7 and J18.9 pins and run the following commands:
# stty -F /dev/ttyLP2 -echo -onlcr 115200 # cat /dev/ttyLP2 & # echo hello > /dev/ttyLP2
For each invocation of echo command the "hello" string should appear on the terminal.
Disabling UART1
To disable UART1 edit arch/arm64/boot/dts/freescale/fsl-imx8qxp-var-som-common.dtsi under kernel source directory and modify
&lpuart1 { ... status = "okay"; };
to
&lpuart1 { ... status = "disabled"; };
Other UARTs can be disabled in the similar manner.