UART B issues with custom carrier

Autonomous Machines Jetson & Embedded Systems Jetson Orin NX
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1

Hi. Using a custom carrier with Orin NX + SSD, flashed with a image built with Yocto (Jetson Linux release: R35.5.0 JetPack release: 5.1.3)

I’m able to find 2 UARTs: /dev/ttyTCU0 (debug) and /dev/ttyTHS0 (UART A), however, I’m not able to find UART B.

I’m testing by doing a chant between RX with TX and doing picocom at that port and see if I receive my input back.

This makes me confused because, when I boot, this is my dmesg output:

root@p3768-0000-p3767-0000:~# dmesg | grep tty
[    0.000000] Kernel command line: mminit_loglevel=4 console=ttyTCU0,115200 firmware_class.path=/etc/firmware fbcon=map:0 net.ifnames=0 nospectre_bhb ipv6.disable=1 audit=0 ipv6.disable=1 audit=0
[    0.275490] 31d0000.serial: ttyAMA0 at MMIO 0x31d0000 (irq = 65, base_baud = 0) is a SBSA
[    1.882535] printk: console [ttyTCU0] enabled
[    3.756296] 3100000.serial: ttyTHS0 at MMIO 0x3100000 (irq = 17, base_baud = 0) is a TEGRA_UART
[    3.771035] 3130000.serial: ttyTHS3 at MMIO 0x3130000 (irq = 63, base_baud = 0) is a TEGRA_UART
[    3.785787] 3140000.serial: ttyTHS4 at MMIO 0x3140000 (irq = 64, base_baud = 0) is a TEGRA_UART
[    7.382253] systemd[1]: Created slice Slice /system/getty.
[    7.383918] systemd[1]: Created slice Slice /system/serial-getty.
[    8.187436] usb 1-2: FTDI USB Serial Device converter now attached to ttyUSB0
[    8.222714] usb 1-2: FTDI USB Serial Device converter now attached to ttyUSB1
[    8.472178] usb 1-2: FTDI USB Serial Device converter now attached to ttyUSB2
[    8.491034] usb 1-2: FTDI USB Serial Device converter now attached to ttyUSB3

So it looks like I have 3 UARTS, but they are different from what I can test?

I think the UART I’m not able to get is the one related to M.2 KEY E. Do I have to enable something extra? (even tho I find it weird it appears 3 uarts available on the dmesg.)

Also, I get different addresses from what Ive seen in other posts in this forum:

        UART0 => UART2(PX04, PX05, PX06, PX07): uartb@3110000 (serial1) - Unused => To M.2 Key E
        UART1 => UART1(PR02, PR03, PR04, PR05): uarta@3100000 (serial0) - /dev/ttyTHS0 => General UART
        UART2 => UART3(PCC05, PCC06): uartc@c280000 (serial2) - /dev/ttyTCU0 => Debug

I dont have any c280000 or 3110000.

Could someone help?

2

From what I understand, in the device tree I could find

serial@3100000 {/* UARTA, for 40 pin header */
    status = "okay";
};

mttcan@c310000 {
    status = "okay";
};

serial@3140000 {
    /* UARTE, Goes to M2.E and also some of the pins to bootstrap */
    status = "okay";
};

serial@31d0000 {/* UARTI - SBSA */
    status = "okay";
};

but no serial@3110000 which refers to uartb.

Im not sure why are there so many UARTs, since Orin NX has only 3.

Adding a new node:

serial@3110000 {/* UARTB */
    status = "okay";
};

seems like it worked:

[    3.746453] 3100000.serial: ttyTHS0 at MMIO 0x3100000 (irq = 17, base_baud = 0) is a TEGRA_UART
[    3.761178] 3110000.serial: ttyTHS1 at MMIO 0x3110000 (irq = 63, base_baud = 0) is a TEGRA_UART
[    3.776142] 3130000.serial: ttyTHS3 at MMIO 0x3130000 (irq = 64, base_baud = 0) is a TEGRA_UART
[    3.790859] 3140000.serial: ttyTHS4 at MMIO 0x3140000 (irq = 65, base_baud = 0) is a TEGRA_UART
4

Hi robyawyx,

For UART-B, it should be the one from M.2 Key E.
Please enable serial@3110000 node in device tree and you should see it from dmesg. → seems you’ve verified it in your 2nd response.

These 2 UARTs seem the virtual one used for debug.
You can check if they are created by nvgetty,

uartc@c280000 is the one reserved when you disable Tegra Combined Uart (/dev/ttyTCU0) and use it as normal UART, but we don’t support and verify this use case yet.

5

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