i.MX6Q (TQIMX6Q/TQE9) Study Notes——UART Transplantation of New BSP

We have configured the system UART when the kernel started, but the tqimx6q development board has brought out the 5-way TTL interface of imx6q, among which uart1 and uart2 are converted to 232 interfaces. This article will configure these 5-way Uart interfaces.

DTS Configuration

Since the kernel already has the uart controller driver for imx6q, we only need to configure the pinctrl of each port. According to the schematic diagram of tqimx6q, we make the following modifications to our DTS:

...

&uart1 {

pinctrl-names = "default";

pinctrl-0 = <&pinctrl_uart1_2>;

status = "okay";

};

&uart2 {

pinctrl-names = "default";

pinctrl-0 = <&pinctrl_uart2_3>;

status = "okay";

};

&uart3 {

pinctrl-names = "default";

pinctrl-0 = <&pinctrl_uart3_2>;

status = "okay";

};

&uart4 {

pinctrl-names = "default";

pinctrl-0 = <&pinctrl_uart4_1>;

status = "okay";

};

&uart5 {

pintctrl-names = "default";

pinctrl-0 = <&pinctrl_uart5_1>;

status = "okay";

};

...

&iomuxc {

pinctrl-names = "default";

uart1 {

pinctrl_uart1_2: uart1grp-2 {

fsl,pins = <

MX6QDL_PAD_SD3_DAT7__UART1_TX_DATA 0x1b0b1

MX6QDL_PAD_SD3_DAT6__UART1_RX_DATA 0x1b0b1

MX6QDL_PAD_EIM_D20__UART1_RTS_B 0x1b0b1

MX6QDL_PAD_EIM_D19__UART1_CTS_B 0x1b0b1

>;

};

};

uart2 {

pinctrl_uart2_3: uart2grp-3 {

fsl,pins = <

MX6QDL_PAD_EIM_D26__UART2_TX_DATA   0x1b0b1

MX6QDL_PAD_EIM_D27__UART2_RX_DATA   0x1b0b1

MX6QDL_PAD_EIM_D28__UART2_CTS_B 0x1b0b1

MX6QDL_PAD_EIM_D29__UART2_RTS_B 0x1b0b1

>;

};

};

uart3 {

pinctrl_uart3_2: uart3grp-2 {

fsl,pins = <

MX6QDL_PAD_EIM_D24__UART3_TX_DATA 0x1b0b1

MX6QDL_PAD_EIM_D25__UART3_RX_DATA 0x1b0b1

>;

};

};

uart5 {

pinctrl_uart5_1: uart5grp-1 {

fsl,pins = <

MX6QDL_PAD_KEY_COL1__UART5_TX_DATA 0x1b0b1

MX6QDL_PAD_KEY_ROW1__UART5_RX_DATA 0x1b0b1

>;

};

};

};

After the modification, recompile and burn the DTB. The new DTB can start the kernel normally.

Test Methods

There are many ways to test the serial port. You can write a special test program to test it. There are a lot of information about this on the Internet, so I won’t give examples here. This article uses a lazy way to temporarily modify bootargs in uboot to the following content:

setenv bootargs 'noinitrd console=ttymxc1,115200 root=/dev/mmcblk0p1 rw rootfstype=ext4 init=/linuxrc'

Then execute the boot command. At this time, the serial terminal connected to uart2 can see the kernel boot log, and of course, you can enter the Linux console normally. The other three serial ports are TTL. I don't have such a level conversion module, so I won't test it.

At this point, all serial ports of tqimx6q have been ported.