LTE

[Ali Alaei]

I am using the M.2 connector on the Radxa Rock 5B+ board to connect an LTE module (EM7455). According to the datasheet and engineers, this M.2 slot is connected to the board via a USB hub (USB 2.0).

When using the official Radxa OS, I can successfully detect the module under lsusb, the necessary kernel modules load correctly, ModemManager recognizes the modem, and I can establish an internet connection.

However, on Armbian, I am experiencing a strange issue. The device does not consistently appear under lsusb; instead, the logs show that it keeps connecting and disconnecting in an endless loop. I am unsure of the root cause and how I can gather more detailed logs.

Since I am dual-booting with the official Radxa OS (Debian) and the modem works fine there, I believe this is not a hardware issue. Below are the relevant dmesg logs for further analysis.(dmesg)

[  115.811271] qcserial 4-1.4:1.0: Qualcomm USB modem converter detected
[  115.8Preformatted text12190] usb 4-1.4: Qualcomm USB modem converter now attached to ttyUSB0
[  116.882327] usb 4-1.4: USB disconnect, device number 9
[  116.883136] qcserial ttyUSB0: Qualcomm USB modem converter now disconnected from ttyUSB0
[  116.883201] qcserial 4-1.4:1.0: device disconnected
[  130.325805] usb 4-1.4: new high-speed USB device number 10 using ehci-platform
[  130.524496] usb 4-1.4: New USB device found, idVendor=1199, idProduct=9070, bcdDevice= 0.00
[  130.524554] usb 4-1.4: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[  130.524584] usb 4-1.4: Product: Sierra Wireless EM7455 Qualcomm
[  130.524610] usb 4-1.4: Manufacturer: Sierra Wireless, Incorporated
[  130.524636] usb 4-1.4: SerialNumber: LF{XXX}
[  130.527209] qcserial 4-1.4:1.0: Qualcomm USB modem converter detected
[  130.528144] usb 4-1.4: Qualcomm USB modem converter now attached to ttyUSB0
[  131.602614] usb 4-1.4: USB disconnect, device number 10
[  131.603279] qcserial ttyUSB0: Qualcomm USB modem converter now disconnected from ttyUSB0
[  131.603339] qcserial 4-1.4:1.0: device disconnected
[  145.045108] usb 4-1.4: new high-speed USB device number 11 using ehci-platform
[  145.243503] usb 4-1.4: New USB device found, idVendor=1199, idProduct=9070, bcdDevice= 0.00
[  145.243521] usb 4-1.4: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[  145.243528] usb 4-1.4: Product: Sierra Wireless EM7455 Qualcomm
[  145.243535] usb 4-1.4: Manufacturer: Sierra Wireless, Incorporated
[  145.243540] usb 4-1.4: SerialNumber: LF{XXX}
[  145.244431] qcserial 4-1.4:1.0: Qualcomm USB modem converter detected
[  145.244712] usb 4-1.4: Qualcomm USB modem converter now attached to ttyUSB0
[  146.322437] usb 4-1.4: USB disconnect, device number 11
[  146.323113] qcserial ttyUSB0: Qualcomm USB modem converter now disconnected from ttyUSB0
[  146.323183] qcserial 4-1.4:1.0: device disconnected
[  159.751520] usb 4-1.4: new high-speed USB device number 12 using ehci-platform
[  159.949674] usb 4-1.4: New USB device found, idVendor=1199, idProduct=9070, bcdDevice= 0.00
[  159.949698] usb 4-1.4: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[  159.949705] usb 4-1.4: Product: Sierra Wireless EM7455 Qualcomm
[  159.949711] usb 4-1.4: Manufacturer: Sierra Wireless, Incorporated
[  159.949717] usb 4-1.4: SerialNumber: LF{XXX}
[  159.950592] qcserial 4-1.4:1.0: Qualcomm USB modem converter detected
[  159.950877] usb 4-1.4: Qualcomm USB modem converter now attached to ttyUSB0
[  161.028727] usb 4-1.4: USB disconnect, device number 12
[  161.029336] qcserial ttyUSB0: Qualcomm USB modem converter now disconnected from ttyUSB0
[  161.029399] qcserial 4-1.4:1.0: device disconnected

 

I tried blocking the `qcserial` driver, but it keeps connecting and disconnecting in a nonstop loop again. 
Not sure if it could be any power configuration problem “echo ‘-1’ | sudo tee /sys/module/usbcore/parameters/autosuspend”  didn't help me.
MoreDetaildLogs: https://paste.next.armbian.com/iwiqanihuw 

LTE Module: Sierra Wireless EM7455 Qualcomm
Linux rock-5b-plus 6.1.99-vendor-rk35xx
Distributor ID: Ubuntu
Description:    Armbian 25.2.2 noble
Release:        24.04
Codename:       noble

Edited 18 hours ago by Ali Alaei

[Igor]

1 hour ago, Ali Alaei said:

official Radxa OS

 

OS is not involved into this, hardware interface (kernel) determines if things works or not and how well. We are using latest Rockchip kernel and this might work better in previous, still in use by Radxa. Guessing that you are using some 5.10.y or 6.1.75 ... since you forgot to tell the most important information  

 

1 hour ago, Ali Alaei said:

Linux rock-5b-plus 6.1.99-vendor-rk35xx

Try with mainline based kernel 1st, https://docs.armbian.com/User-Guide_Armbian-Config/System/#install-alternative-kernels -> current , where such hardware usually works better. Or try older vendor kernels, that might be the same as in Radxa OS.

[Ali Alaei]

Ops sorry forgot to mention (6.1.84-1-rk2410) is the kernel version in my functional Radxa OS.
In Armbian I switched to this version (6.1.84-vendor-rk35xx). The issue still remains. (I used armbian-config --cmd SY201 to change the kernel). Any suggestion what I am doing wrong?
Logs: https://paste.armbian.com/celonaqecu

[Igor]

Let's ping Radxa engineers if they have a clue on this

@RadxaYuntian

otherwise I propose trying CURRENT kernel. That should be generally more reliable in those things.