RM500Q-AE Module keeps resetting under heavy load

I am running RM500QAEAAR11A02M4G.

My connection is:
+QENG: “servingcell”,“NOCONN”
+QENG: “LTE”,“FDD”,310,260,14B2701,93,66786,66,5,5,2C46,-116,-15,-79,10,0,-32768,8
+QENG: “NR5G-NSA”,310,260,65535,-32768,-32768,-32768

When I run a bandwidth test the modem will transfer at a high rate and then a short while after it will go into reset. In another terminal, minicom tells me that the modem has disconnected from /dev/ttyUSB3. The modem will then come back and reconnect in a fresh state, search for the tower and lock on again.

Is this a known issue? Would a firmware upgrade help? This instability makes the module not very useful.

Also, in the documentation for AT commands here, it states that AT+QSCAN takes an option ext parameter (AT+QSCAN=[,]). Issuing this to my device results in an error and I can’t get it to display extra information.


If it helps, my router (OpenWRT) has these entries in the dmesg log. The module is plugged into a M.2->USB3 module.

[ 3439.931334] usb 2-2: USB disconnect, device number 7
[ 3439.936709] option1 ttyUSB0: GSM modem (1-port) converter now disconnected from ttyUSB0
[ 3439.944861] option 2-2:1.0: device disconnected
[ 3439.949892] option1 ttyUSB1: GSM modem (1-port) converter now disconnected from ttyUSB1
[ 3439.957982] option 2-2:1.1: device disconnected
[ 3439.962719] option1 ttyUSB2: GSM modem (1-port) converter now disconnected from ttyUSB2
[ 3439.970747] option 2-2:1.2: device disconnected
[ 3439.975585] option1 ttyUSB3: GSM modem (1-port) converter now disconnected from ttyUSB3
[ 3439.983682] option 2-2:1.3: device disconnected
[ 3439.992556] qmi_wwan 2-2:1.4 wwan0: unregister ‘qmi_wwan’ usb-0000:01:00.0-2, WWAN/QMI device
[ 3440.314691] qmi_wwan 2-2:1.4: Tx URB error: -19
[ 3440.319499] qmi_wwan 2-2:1.4: Tx URB error: -19

This is a very common occurrence when the power supply to the modem is not adequate. It is unlikely to happen due to any other cause.

Thanks for the info. This is running on a Raspberry Pi 4, so it might not be supplying enough current.

What is the peak load? I could only find figures for sleep and idle.

The power supply is capable of providing a sufficient current of at least 5A.

Quoted from the RM50xQ Series Hardware Design document.

I don’t know how much my RM500Q-AE has available, but it’s stable with less than 5A.

Pulling 5 amps through a USB port sounds like a recipe for magic smoke. Regular USB3 ports are rated for 0.9A.

I use these: Dual-Q M.2 (NGFF) Key B to USB3.0 adapter Enclosure fit for 5GNR M.2 Quectel RM500Q RM510Q – 4G discount

This uses a second USB port for extra power. USB cables should have 22AWG or thicker power wires for these modems, and be as short as practicable.

This is an even better choice: USB3 to NGFF M.2 Key B 4G 5G Modem Adapter Enclosure with SIM Slot

Note the improved secondary power input.

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