ongone93 asked 7 days ago
I working on a friend project. I want to send message alert using the sim800c module. Does anyone ever used the esp32 with the sim800c module, and have the correct connection pins.
Sara Santos Staff answered 6 days ago
Hi.
I never used that module.
I found this image for the pinout: 
You need to connect the TX and RX pins to the ESP32 UART pins:
- UART0: (GPIO 1 and GPIO3)
- UART2: (GPIO 17 and GPIO 16)
The other pins, I don’t know what they mean.
Regards,
Sara
Steve Mercer answered 3 days ago
Just search for SIM800L projects. Something like this instructable. The only difference is that the ‘C’ version includes Bluetooth (Which is superfluous as the ESP32 already has BLE) and the ‘L’ version swaps that for FM.
As the SIM800 is basically a cell phone module, the ‘SPK’ lines are for a speaker and the ‘MIC’ lines are for a microphone.
All you need to connect is VCC, GND, TX and RX.