EC21 get freeze using REST after some hours


Module has to send via AT commands some system telemetry using REST (mostly via POST methods) protocol.

After some hours (between 16-20h) module stop writing back any information over TXD pin.

To test modem status, I tried to plug in to the PC using the USB. All COM ports are created correctly but computer didn’t receive any answer when commands like AT or ATI are sent.

Could it be a internal memory leak?

Firmware Revision: EC21EFAR06A02M4G


Could you please send me back if there is any FW update?

Thanks so much.


Excuse me, there are multiple tests. Is this true every time?I can‘t give you a prefect answer but i can give you a different FW.



Yes. It happens always but with random times (after some hours).

Do I have the latest version of the FW?

Edit: I just see your email. Let me update the module and reply to you if the problem continues.


Ok,you can have a try,

Hi Witt
Sadly it happens again after FW update, EC21 stop writing data on the Tx UART port. I’d check that host microcontroller continues sending data and it arrives to RX pin to modem. Quectel USB AT Port get froze too (deployed but no answers from it).

Signals levels with and without the error are (measured on modem pads):

Rx: 1.71V
Tx : 1.78V
DTR: 1.77V (Not connected)
RTS: 1.71V (Not used)
CTS: 0V (Not used)
DCD: 1.79V (Not connected)
RI: 1.79V (Not connected)
Status: 200mV (Not used)

Any idea why this could happend? What can I test to get any solution?



It feels like your problem is a memory leak, I’m giving you a similar firmware for you to try

And this is the latest FW I can get :eyes:

Thanks Witt,

I’m going to test the two firmwares during this 2 days.

Does EC21 have any command to monitor memory consumption?

Could a little power supply voltage drop cause that EC21 microcontroller get freeze but USB component (I don’t know if it works in a separate chip) continue working?

Hi Ismael

I am so sorry that there is no command to query memory consumption.

About the second question,a little power supply voltage drop may cause the situation you describe.

would someone from you be so kind as to send me a link to the newer firmware for Quectel
Revision: EC21EFAR06A01M4G