ESP32 + SIM800L - GSM module not registering on network after initial setup.
Sprunki.Retake 2025-09-18 15:00:34 104 Views1 Replies Hello,
I’ve finally got my ESP32 and SIM800L module talking via UART, and it registers to the network fine the first time I power it up. But if I reset the ESP32 without fully powering down the SIM800L, it fails to register. I have to cycle the SIM800L’s power to get it to connect again. Is there a specific AT command to “re-register” the module that I’m missing, or is this a common behavior for the SIM800L?
Thanks for any help!
Most people building ESP32 + SIM800L projects will:
Either tie the SIM800L’s PWRKEY pin to an ESP32 GPIO so they can “reboot” it in software when needed.
Or, in firmware, issue AT+CFUN=1,1 during initialization to ensure the SIM800L always starts from a clean state after the ESP32 reset. If you want fast recovery without fully power-cycling, I recommend adding AT+CFUN=1,1 in your ESP32’s init sequence. That’s the closest to a proper reset command.
You can see a tutorial using SIM800L here. https://www.theengineeringprojects.com/2022/10/interactive-voice-response-system-with-raspberry-pi-4-sim800l.html
ahsrab.rifat 