Im working on a project using an Arduino Nano and a SIM800C GSM module where I need to record phone calls directly to an external SD card. However, I’m unsure which AT commands to use and how to configure the setup for this functionality. The SIM800C documentation hasn’t provided clear instructions on how to achieve this.

What I Need:

1. AT commands that support starting, stopping, and managing call recording to an SD card.
2. Command sequence and steps required to correctly initiate and manage call recording during an active call, and ensure it’s saved to the SD card.
3. Any example code or detailed steps that could guide me in implementing this functionality.

What I’ve Tried:
I’ve successfully initiated and answered calls with the following AT commands:

1. ATD+;
2. AT+CREC – Results In ERROR, I suspect that either the command is incorrect or additional steps are required.

Questions:

1. What are the correct AT commands to record a call and save it to an external SD card using the SIM800C module?
2. Is there a specific sequence or additional setup needed to achieve this?
3. Can anyone provide a working example or detailed instructions on how to implement call recording to an SD card with this module?
4. Any guidance or example code would be greatly appreciated. Thank you!