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UART4 can't receive data

Question asked by Pierre-Olivier Huard on Oct 19, 2016
Latest reply on Oct 19, 2016 by igorpadykov

Hello

I'm currently trying to receive data throught UART4, but it does not work. I can send data (on iMX6 with echo -en "hello" > /dev/ttymxc3) and it works, but when I do cat /dev/ttymxc3, I receive nothing from the host PC. I probed the RX pin, the data is correct.

This is my configuration :

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

&uart4 {
      pinctrl-names = "default";
      pinctrl-0 = <&pinctrl_uart4>;
      status = "okay";
};

The registers for the Daisy chain seems to be set rightly:

IOMUXC_SW_MUX_CTL_PAD_KEY_COL0:0x020e01f8 =0x00000004

IOMUXC_SW_MUX_CTL_PAD_KEY_ROW0:0x020e01fc =0x00000004

IOMUXC_UART4_UART_RX_DATA_SELECT_INPUT:0x020e0938 =0x00000001

 

You will find attached two images, with the data on TX (in yellow) and RX (in blue), the data is decoded for more visibility. The sent data is correct, the received data also, but not displayed in linux  so I think there is an error somewhere.

 

I'm on iMX6Q, Kernel 3.14.38.

Best Regards,

Pierre-Olivier

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