Can't Enable ttyTHS4 (UART5) on Jetson Orin Nano with reComputer J401 Carrier Board

[keiichiro1.koyama]

Hi,

I’m trying to enable UART5 (/dev/ttyTHS4) on a Jetson Orin Nano 8GB using the Seeed Studio reComputer J401 carrier board, but the pinmux settings don’t seem to apply, and the port does not appear after reboot. Below is a summary of what I have done so far.

Environment

・Jetson SoC: Jetson Orin Nano 8GB
・Carrier Board: Seeed Studio reComputer J401
・JetPack / L4T: R35.5.0
・Goal: Enable /dev/ttyTHS4 (UART5) for communication
・Pins Used: Pin 31 (TX), Pin 29 (RX) on the 40-pin header (UART5 on J401)

What I’ve tried

1. Created a device tree overlay uart5-enable.dts:

/dts-v1/;
/plugin/;

/ {
compatible = “nvidia,jetson-orin-nano-devkit”;

fragment@0 {
    target-path = "/serial@3140000";
    __overlay__ {
        status = "okay";
    };
};

fragment@1 {
    target-path = "/pinmux@2430000";
    __overlay__ {
        uart5_pinmux: uart5_pinmux {
            nvidia,pins = "uart5_tx", "uart5_rx";
            nvidia,function = "uart";
            nvidia,pull = <0>;
            nvidia,tristate = <0>;
        };
    };
};

};

Built it using:
dtc -I dts -O dtb -o uart5-enable.dtbo uart5-enable.dts
sudo cp uart5-enable.dtbo /boot/

2. Edited `/boot/extlinux/extlinux.conf:

I added this to the APPEND line:
overlay_dtbo=uart5-enable.dtbo

(I made sure the APPEND line is a single line and syntax is valid.)

3. Rebooted and checked the result:
   ls /dev/ttyTHS4

→ found

sudo cat /sys/kernel/debug/pinctrl/2430000.pinmux/pinmux-pins | grep uart5

→ No output

Confirmed
・uart5-enable.dtbo exists in /boot/
・No typos or syntax errors in extlinux.conf
・No conflicting overlays
・Seeed’s documentation confirms that Pin 31 and 29 are mapped to UART5 (TX/RX)

Questions
・Is there anything additional required to enable UART5 (ttyTHS4) on Orin Nano using the J401 carrier board?
・Is placing .dtbo in /boot/ sufficient for L4T R35.5.0, or does it need to be in another directory (e.g., /boot/dtb/overlays/)?
・Are "uart5_tx" and "uart5_rx" correct for nvidia,pins when targeting UART5 on this platform?

Additional Notes
・I successfully disabled nvgetty and confirmed that ttyTHS0 works for general communication.
・I also tried a similar approach with ttyTHS3 (UART4), but the pinmux state did not change there either.

Any help or insight would be greatly appreciated.
Thank you!

[KevinFFF]

Hi keiichiro1.koyama,

@keiichiro1.koyama

・Pins Used: Pin 31 (TX), Pin 29 (RX) on the 40-pin header (UART5 on J401)

Sorry that I’m not clear about your custom carrier board since PIN29/PIN31 on official Orin Nano devkit is not used for UART.
It should be the custom design by your vendor, please contact them for the usage.

You can check dmesg to know if there’s any error showing during boot up to probe your serial interface.