UART4 can't receive data

pierre-olivierh — Wed, 19 Oct 2016 13:28:46 GMT

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

Re: UART4 can't receive data

igorpadykov — Wed, 19 Oct 2016 23:48:01 GMT

Hi Pierre-Olivier

uart4 is used on sabre-ai board, imx6qdl-sabreauto.dtsi
http://git.freescale.com/git/cgit.cgi/imx/linux-2.6-imx.git/tree/arch/arm/boot/dts/imx6qdl-sabreauto.dtsi?id=rel_imx_4.1.15_1.2.0_ga

Schematics (5)
Design files for i.MX 6Quad and i.MX 6DualLite CPU1 Cards
Design files for Base Board (REV E)

http://www.nxp.com/products/software-and-tools/hardware-development-tools/sabre-development-system/sabre-for-automotive-infotainment-based-on-the-i.mx-6-series:RDIMX6SABREAUTO?fpsp=1&tab=Design_Tools_Tab

Best regards
igor
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UART4 can't receive data

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