I am using sim800c gsm module.
It is showing some weird problems that am not able to figure out.
The at commands are working fine.
The problem is that, the module stops working after inserting the sim card. After the power button is pressed, it gives the following messages:
RDY, +CFUN: 1, +CPIN: READY, Call Ready.
After this, the module stops working, the led stops blinking. If i don't insert sim card this won't happen.
The power supply is proper 4.1 v 3A, even i tested with 4V battery there also it shows the same problem. So I don't think this is power supply problem.
I tried with different sim cards and got the same result.
this is the circuit diagram
Best Answer
It only tries to register when it has a SIM.
To register, it must transmit.
Either the supply voltage drops when it transmits and causes the processor to hang, or the RF is getting somewhere and causing problems.
I don't see a bypass capacitor on your power supply in, though there may be one on the module.
You may also need a large capacitor on Vbat to help with the current peaks when the module transmits.