Quectel RM502Q-AE Diagnose Random Connection Loss

[proto]

Hello Everyone,

I have a RM502Q-AE in a USB sled and a GL-B1300 Flashed with Rooter from 3/16/2021.

The USB Sled is powered via the Router USB and AUX USB. The system works really great most of the time, but sometimes, rarely, the internet connection stops working. If I reboot the router it will usually start working again. It will also start working if I click the Reset USB 1 and Reset USB 2 buttons on the "admin/modem/misc" page.

I was wondering if there were any AT commands I could use to diagnose this when the internet connection stops working. Everything looks normal on the Rooter Modem Network Status page when this is happening.

Other info:
Modem : Quectel RM502Q-AE
Modem ID : 2c7c : 0800
Provider : T-Mobile
Comm Port : /dev/ttyUSB2
Protocol : MBIM

All of these AT commands executed while the connection is working:

ATI
Quectel
RM502Q-AE
Revision: RM502QAEAAR11A02M4G

AT+QNWPREFCFG="mode_pref"
+QNWPREFCFG: "mode_pref",AUTO

AT+CGDCONT?
+CGDCONT: 1,"IPV4V6","fast.t-mobile.com","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0,,,,,,,,,"",,,,0
+CGDCONT: 2,"IPV4V6","ims","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0,,,,,,,,,"",,,,1
+CGDCONT: 3,"IPV4V6","sos","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,1,,,,,,,,,"",,,,1
+CGDCONT: 4,"IPV4V6","tmus","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0,,,,,,,,,"",,,,0
+CGDCONT: 5,"IPV4V6","h2g2","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0,,,,,,,,,"",,,,0

AT+CSQ
+CSQ: 30,99

AT+CEREG?
+CEREG: 0,1

AT+CGREG?
+CGREG: 0,0

AT+COPS?
+COPS: 0,2,"310260",13

AT+QENG="servingcell"
+QENG: "servingcell","NOCONN"
+QENG: "LTE","FDD",310,260,24F950B,321,1100,2,5,5,8158,-91,-18,-52,9,0,150,-
+QENG:"NR5G-NSA",310,260,65535,-32768,-32768,-32768

Thank you!

[proto]

Same commands when the connection was down. After doing Reset USB 1 and Reset USB 2 it came back on.

Connection Down:

AT+QNWPREFCFG="mode_pref"
+QNWPREFCFG: "mode_pref",AUTO

OK

AT+CGDCONT?
+CGDCONT: 1,"IPV4V6","fast.t-mobile.com","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0,,,,,,,,,"",,,,0
+CGDCONT: 2,"IPV4V6","ims","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0,,,,,,,,,"",,,,1
+CGDCONT: 3,"IPV4V6","sos","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,1,,,,,,,,,"",,,,1
+CGDCONT: 4,"IPV4V6","tmus","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0,,,,,,,,,"",,,,0
+CGDCONT: 5,"IPV4V6","h2g2","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0,,,,,,,,,"",,,,0

OK


AT+CSQ
+CSQ: 31,99

OK

AT+CEREG?
+CEREG: 0,1

OK

AT+CGREG?
+CGREG: 0,0

OK

AT+COPS?
+COPS: 0,2,"310260",13

OK

AT+QENG="servingcell"
+QENG: "servingcell","NOCONN"
+QENG: "LTE","FDD",310,260,24F950B,321,1100,2,5,5,8158,-89,-18,-51,9,0,-32768,34
+QENG:"NR5G-NSA",310,260,65535,-32768,-32768,-32768

OK

[juavos00]

I’m having the same issue here recently with the same card but installed in a usb sled/WG3526 combo. Debug window doesn’t show anything but running at+cfun=1,1 seems to reset it too.

[mlinuxguy]

I have the same issue and have been posting in the ROOter OpenWRT forums about it
Mine is in a WG1608 from The Wireless Haven and I have to reboot the router to get the modem to reconnect
It happens anywhere from 4 or 5 times in a row to every 24 hours.
I have a case open with Quectel and they've hooked me up with the U.S. FAE but he in turn
copied someone in China who hasn't responded in a week.

[juavos00]

I have the same issue and have been posting in the ROOter OpenWRT forums about it
Mine is in a WG1608 from The Wireless Haven and I have to reboot the router to get the modem to reconnect
It happens anywhere from 4 or 5 times in a row to every 24 hours.
I have a case open with Quectel and they've hooked me up with the U.S. FAE but he in turn
copied someone in China who hasn't responded in a week.

Someone on the The Wireless Haven Facebook group said this card is more stable on the Ethernet protocol. I’m kinda weary about changing mine as it could render it unresponsive. I was able to save an EM20 one time after changing to that protocol so I gave up

AT+QCFG=“usbnet”,1 is the command if your inclined to want to try it

[mlinuxguy]

"more stable on the Ethernet protocol"
its not, I tested already switching over to ECM and the difference is the modem's usb ports completely disappear when the TX hang happens. Under QMI at least I can issue AT commands.

[juavos00]

"more stable on the Ethernet protocol"
its not, I tested already switching over to ECM and the difference is the modem's usb ports completely disappear when the TX hang happens. Under QMI at least I can issue AT commands.

Ok thanks for the update, and yes I have mine now in QMI protocol and it seemed to have help some. Please update if you hear anything else from Quectel regarding this issue!

[proto]

Mine is Protocol : MBIM, though I saw similar issues in QMI. Is why I switched to MBIM.

What are the AT commands for various modes?

Thanks!

[juavos00]

AT+QCFG="usbnet",0 - is PPP & QMI (default)
AT+QCFG="usbnet",1 - is ECM.
AT+QCFG="usbnet",2 - is MBIM

Followed by running the command AT+CFUN=1,1