Missing Serial Port

  • Hello!


    I'm trying on getting all 6 UARTs of the PicoCOM1.2 working. We do require all of them for our use case.

    I'm currently seeing only 5 of them (See $ ll /dev | grep ttymxc output below). Not sure if this is missing in the kernel, or I'm missing some configuration in uboot.


    It's noteworthy to state that I've used the default F&S Kernel + Dtb and only have some minor changes in uboot - mainly additional libraries. Tough it also only lists 5 devices with the

    vanilla uboot config.


    Could someone tell me how to get the sixth UART to appear?


    Linux Version

    # uname -a

    Code
    1. Linux fsimx6ul 4.9.88-F+S #1 PREEMPT Thu Jul 1 13:31:41 UTC 2021 armv7l GNU/Linux


    Ttymxc's

    # ll /dev | grep ttymxc

    Code
    1. lrwxrwxrwx 1 root root 12 Jan 1 00:00 login_tty -> /dev/ttymxc0
    2. crw-rw---- 1 root dialout 207, 16 Jan 1 00:02 ttymxc0
    3. crw-rw---- 1 root dialout 207, 17 Jan 1 00:02 ttymxc1
    4. crw-rw---- 1 root dialout 207, 18 Jan 1 00:02 ttymxc2
    5. crw-rw---- 1 root dialout 207, 19 Jan 1 00:00 ttymxc3
    6. crw-rw---- 1 root dialout 207, 22 Jan 1 00:02 ttymxc6


    See attachments for full $ ll /dev output.

  • Working solution, provided by Mr. Kay Müller from F&S:


    Open arch/arm/boot/dts/picocom1.2.dts:

    Remove the comment from line 68 & 69. Add comment-out line 73, such that you have:


    Code
    1. 68 #define CONFIG_PICOCOM1_2_UART_F
    2. 69 #define CONFIG_PICOCOM1_2_UART_F_RTSCTS
    3. 70
    4. 71 /* SPI: SPI_A (3x CS) on pins 55-60, SPI_B (1x CS) on pins 63-66 */
    5. 72 #define CONFIG_PICOCOM1_2_SPI_A
    6. 73 //#define CONFIG_PICOCOM1_2_SPI_B


    Then, run $ make fsimx6ul_defconfig, followed by $ make picocom1.2.dtb.

    You can then flash the new dtb (arch/arm/boot/dts/picocom1.2.dtb) via uboot.