/dev/ttyACM0 changes to /dev/ttyACM1

Hello team,
I have a peculiar problem with my setup. I have connected a RFID Reader to the USB port of the Jetson Nano 2G. After working for few (20/30/50) minutes i have observed that the /dev/ttyACM0 is not found in the nano and my app throws and error. Instead when i do ls /dev/tty*, i see /dev/ttyACM1 being available… After reboot, everything is back to normal.
Can you guide me on why this can happen and how to handle this.
Thanks !!

Does dmesg give any hint about this behavior?

I agree with what @WayneWWW asks…run “dmesg --follows”, and then when the error occurs, note what new logs show up. A key bit of information to know is that USB enumerates devices in the order they are found. If a device disconnects and reconnects, then the old device is discarded and a new device with the next numeric name results. Your device disconnected, and then reconnected, so you need to see logs to see why. Examples of problems would be if the device momentarily required more power than is available, or if signal quality failed. Logs should give a hint at the problem.

I agree and was thinking on the same lines as well. Funny part is that the power is not taken by the RFID reader from the USB, it is powered externally. And more importantly, this phenomenon is happening only with Jetson, not with laptop/PC/RPi… So was a bit surprised and shared, looking for some ideas. Herewith attaching the dmesg response, if anything can come out.
DMESG.log (20.8 KB)
DMESG-1.log (22.6 KB)


It looks like usb some communication problem and then it enumerates the device again after those errors. Actually, the device gets disconnection.

[   30.622777] cdc_acm 1-3.2:1.0: ttyACM0: USB ACM device
[   30.623790] usbcore: registered new interface driver cdc_acm
[   30.623793] cdc_acm: USB Abstract Control Model driver for USB modems and ISDN adapters
[   31.858758] vdd-usb-vbus: disabling
[   31.858762] vdd-usb-vbus2: disabling
[   31.858856] vdd-usb-hub-en: disabling
[  909.813920] usb 1-3.2: USB disconnect, device number 6
[  909.814001] cdc_acm 1-3.2:1.0: acm_ctrl_irq - usb_submit_urb failed: -19
[  910.068843] usb 1-3.2: new full-speed USB device number 7 using tegra-xusb
[  911.084017] usb 1-3.2: Device not responding to setup address.
[  912.311965] usb 1-3.2: Device not responding to setup address.
[  912.524830] usb 1-3.2: device not accepting address 7, error -71
[  912.628791] usb 1-3.2: new full-speed USB device number 8 using tegra-xusb
[  913.643954] usb 1-3.2: Device not responding to setup address.
[  914.871927] usb 1-3.2: Device not responding to setup address.
[  915.084759] usb 1-3.2: device not accepting address 8, error -71
[  915.090854] usb 1-3-port2: attempt power cycle
[  916.440739] tegra-xusb-padctl 7009f000.xusb_padctl: power down UTMI pad 2
[  916.460716] usb 1-3: usb_suspend_both: status 0
[  916.460803] usb usb1: usb_suspend_both: status 0

You are connecting this device to the hub of jetson nano 2gb directly?

BTW, could you just share the full log? No need to grep usb. The original log is always the best.

Sure Wayne. Here it is. We also suspected it earlier and changed the power source for the two devices i.e. Jetson and RFID. But unable to reach the root cause as it shows no error with Windows or even RPi. That’s why a bit surprised. Attached herewith the full log…
DMESG-2.log (58.4 KB)

Yes the device is connected on the upper port of USB2.0 ports available on the device.

I’ll suggest to add a HUB (preferably externally powered) between device and Jetson to see if signal quality changes anything. You could try more than one HUB if available. There is some suggestion that this is often over-current, but I don’t know if that is true for this case since you are already using an external power source.


May I know what kind of RFID reader you are running? Which brand/sku is it?

It is from NordicID UHF RFID reader module. RAIN RFID Reader Modules - Nordic ID Oyj
Rajat Ratra

Is there any retailer website for this module? Didn’t see such info on the link you shared.

PFA some of the documents. Hope this helps !!

DS_Nordic_ID_eNUR05W_v1009.pdf (635.7 KB)
eNUR-Ax_HW_interface_manual_v1_1 (1).pdf (1.1 MB)


I don’t need to know the details about this board.

What I need is how can I buy/get this board?

Here it is…