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UART

UART Overview

The exposes up to nine UART interfaces, some of which are multiplexed with other peripherals. The following serial ports are enabled by default in Variscite's Symphony board device tree:

Serial Port	Device Node	Device Tree	Note
UART0	/dev/ttyS0	main_uart0	Connected to Symphony board serial console
UART2	/dev/ttyS2	main_uart2	Connected to Symphony board J18.7 and J18.9
UART5	/dev/ttyS5	main_uart5	Used on SOM for Bluetooth interface and can be accessible only if the [/blob//recipes-connectivity/bcm43xx-utils/bcm43xx-utils/am62x-var-som/variscite-bt variscite-bt] Systemd service is disabled or SOM without "WBD" and "WB"
UART6	/dev/ttyS6	main_uart6	Connected to Symphony board J18.3 and J18.5

Refer to the SOM datasheet for more information about the other serial ports.

Testing UART2

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

# stty -F /dev/ttyS2 -echo -onlcr 115200
# cat /dev/ttyS2 &
# echo hello > /dev/ttyS2

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/ttyS6 -echo -onlcr 115200
# cat /dev/ttyS6 &
# echo hello > /dev/ttyS6

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

Disabling UART6

To disable UART5 edit arch/arm64/boot/dts/ti/ under kernel source directory and modify

&main_uart6 {
        ...
        status = "okay";
};

to

&main_uart6 {
        ...
        status = "disabled";
};

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