Colibri imx6ull uart3.TX uart3.RX mixed up?

Technical Support
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1

Hi,

I am currently testing UART_E (uart3 in colibri imx6ull data sheet) on our custom carrier board. I have modified imx6ull-colibri.dtsi to use uart3 for RS485:

    pinctrl_uart3: uart3-grp {
    		fsl,pins = <
    			MX6UL_PAD_UART3_TX_DATA__UART3_DTE_RX	0x1b0b1 /* SODIMM 135 */
    			MX6UL_PAD_UART3_RX_DATA__UART3_DTE_TX	0x1b0b1 /* SODIMM 77 */
    		>;
    	};
   ...
    &uart3 {
    	pinctrl-names = "default";
    	pinctrl-0 = <&pinctrl_uart3 &pinctrl_uart3_ctrl3>;
    	rts-gpios = <&gpio5 6 GPIO_ACTIVE_HIGH>;
    };

And imx6ull-colibri-aster.dtsi (for testing I did not create our own *.dtsi for our carrier board, I have just modified the imx6ull-colibri-aster.dtsi):

&uart3 {
	status = "okay";
};

When I send something to RS485 transceiver, the data are sent through UART_E_RX (SODIMM pin135, uart3.tx in colibri imx6ull data sheet). I have checked it with oscilloscope. But the data should be sent through UART_E_TX (SODIMM pin77, uart3.rx in colibri imx6ull data sheet), right?

I have tested UART_D for comparison. On the UART_D data are sent through UART_D_TX (SODIMM pin96, uart6.rx in imx6ull colibri data sheet) as expected.
device tree changes on imx6ull-colibri.dtsi:

pinctrl_uart6: uart6-grp {
fsl,pins = <
MX6UL_PAD_CSI_MCLK__UART6_DTE_RX  	0x1b0b1 /* SODIMM 75 */
MX6UL_PAD_CSI_PIXCLK__UART6_DTE_TX	0x1b0b1 /* SODIMM 96 */
MX6UL_PAD_ENET1_TX_EN__UART6_DTE_CTS 0x1b0b1 /* SODIMM 30 */
MX6UL_PAD_ENET1_TX_DATA1__UART6_DTE_RTS 0x1b0b1 /* SODIMM 73 */
   >;
};
...
&uart6 {
	pinctrl-names = "default";
	pinctrl-0 = <&pinctrl_uart6>;
	fsl,uart-has-rtscts;
	fsl,dte-mode;
};

So one of this UARTs has wrong description in data sheet? or I have made a mistake somewhere?

Best regards,
Taras

2

Please note fsl,dte-mode; line at &uart6

From Colibri iMX6ull datasheet:

The UARTs of the i.MX 6ULL can be configured either in the DTE (Data Terminal Equipment) or DCE
(Data Communication Equipment) mode. Changing the mode will change the direction of all UART
pins (data and all control signals). To ensure compatibility with the entire Colibri family, UARTs
need to be configured in DTE mode.

3

Thank you, it works now

4

Thank you for the update.