RE: How to detect if a SIM card is not inserted at startup

KatoTakayuki — Thu, 26 Feb 2026 00:54:51 GMT

Thanks, your constant support.

This board is a prototype, "SIM DETECT" method is difficult. (Low priority and mass production costs)

What are the "needed AT commands"?
Are there any other options besides "AT%XSIM?" and "AT+CPIN?"

Best regards,

Kato.

RE: How to detect if a SIM card is not inserted at startup

Simon D-M — Wed, 25 Feb 2026 12:33:28 GMT

Hi,

If you are doing a custom PCB, you might want to find a SIM card socket that has a "SIM_DETECT" pin and connect it to a GPIO on the microcontroller. That would be the easiest and fastest way to check if a SIM card is present or not in the socket.

If you cannot do that for some reason, you can try to send the needed AT commands by yourself, it might be faster than going through the full LTE api. But this method is still way longer and power hungry than the GPIO pin solution.

I hope I was able to help. If you have any more questions, feel free to ask.

Best regards,

Simon D-M