Test available UART in iMX6Sabre

[kunalkulshresth]

Hi All,

I am trying to test UART3 i.e. enabled as ttymxc2 in iMX6DLsabreauto board which I am working on. What I tried is to send data from UART3 TX to UART4 RX(configured as console) and check if the sent data is seen at minicom, so test passes. I am facing some issues with the test. Generally not able to check the success. Wanted to know if the approach looks ok, or do I need to do more changes to make this happen? I connected Pin 8 of U17 chip (BT_WIFI_UART3_TXD/SD4_CMD) to the RX of debug port(P{in 3 of J18).

Attached are some related documents (schematic, dts etc.). Any help will be appreciated.

        pinctrl_uart3_1: uart3grp-1 {
            fsl,pins = <
                MX6QDL_PAD_SD4_CLK__UART3_RX_DATA    0x1b0b1
//                MX6QDL_PAD_SD4_CMD__UART3_TX_DATA    0x1b0b1
                MX6QDL_PAD_EIM_D30__UART3_CTS_B        0x1b0b1
                MX6QDL_PAD_EIM_EB3__UART3_RTS_B        0x1b0b1
            >;
        };

        pinctrl_uart3dte_1: uart3dtegrp-1 {
            fsl,pins = <
                MX6QDL_PAD_SD4_CLK__UART3_TX_DATA    0x1b0b1
                MX6QDL_PAD_SD4_CMD__UART3_RX_DATA    0x1b0b1
                MX6QDL_PAD_EIM_D30__UART3_RTS_B        0x1b0b1
                MX6QDL_PAD_EIM_EB3__UART3_CTS_B        0x1b0b1
            >;
        };

        pinctrl_uart4: uart4grp {
            fsl,pins = <
                MX6QDL_PAD_KEY_COL0__UART4_TX_DATA    0x1b0b1
                MX6QDL_PAD_KEY_ROW0__UART4_RX_DATA    0x1b0b1
            >;
        };

Thanks and regards,

KK

[weidong_sun]

Hello Kunal,

     Your test approach should be OK, UART3_RXD will receive messages from UART4_TXD, but I checked your schematic, There is no Test Point on UART4_TXD line, I don't konw how you can connect these two lines together! so you should ensure the phsical conntections between UART3_RXD and UART4_TXD at first.

     According to you schematic, I think if you really wants to test if UART3_RXD normally works, hardware engineer can check it's wave form by oscilloscope during receiving data.

Hope above advice can help you!
Have a great day,
Weidong

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[kunalkulshresth]

@Weidong, All

Thanks. I meant UART3_TXD to be plugged into UART4_RXD (which is configured as console). Progress is that I have been able to detect data on UART3_TX line after dtsi changes. Ofcourse, I had to pull out pin from pin8 of U17 for Tx. But when I connect this pin to pin3 of J18 (which is debug Rx) I was of understanding that the data sent (echo 101 > /dev/ttymxc2) will echo on console. But it does not. Any ideas here?

Thanks and regards,

Kunal