DART-6UL UART

DART-6UL - External UART

Test

By default, Variscite configured UART1, ttymxc2. to test:

Use minicom to connect.
Set the serial to ttymxc2.
You can use a loopback or connect to anther computer.
The pin's are coming out from J9 connector.

Example: configure UART4, ttymxc3

Edit arch/arm/boot/dts/imx6ull-var-dart.dts Look for:

/* ttymxc2 UART */
&uart3 {
	pinctrl-names = "default";
	pinctrl-0 = <&pinctrl_uart3>;
	fsl,uart-has-rtscts;
	status = "okay";
};

Duplicate it and change the name and the pinctrl name. For Example:

&uart4 {
	pinctrl-names = "default";
	pinctrl-0 = <&pinctrl_uart4>;
	fsl,uart-has-rtscts;
	status = "okay";
};

Duplicate the corresponding pinctrl. Copy :

		pinctrl_uart2: uart2grp {
			fsl,pins = <
				MX6UL_PAD_UART2_TX_DATA__UART2_DCE_TX	0x1b0b1
				MX6UL_PAD_UART2_RX_DATA__UART2_DCE_RX	0x1b0b1
				MX6UL_PAD_UART2_CTS_B__UART2_DCE_CTS	0x1b0b1
				MX6UL_PAD_UART2_RTS_B__UART2_DCE_RTS	0x1b0b1
			>;
		};

Into:

		pinctrl_uart4: uart4grp {
			fsl,pins = <
                                MX6UL_PAD_UART4_TX_DATA__UART3_DCE_TX   0x1b0b1
                                MX6UL_PAD_UART4_RX_DATA__UART4_DCE_RX   0x1b0b1
				MX6UL_PAD_ENET1_RX_DATA1__UART4_DCE_CTS	0x1b0b1
				MX6UL_PAD_ENET1_RX_DATA0__UART4_DCE_RTS	0x1b0b1
			>;
		};

The pins are set arbitrary. You should set them based on your hardware design.