How can I reset SIM900 when it does not respond to AT commands? The problem is when I`m trying to send some files over the gprs network, but sometimes, i dont get response from network, and after timeout im not able to execute at commands normally for some time ( i suppose sim900 is still waiting ).. So, how i can reset sim900 or tell him not to wait anymore?
SIM900 support the reset function, when the MCU find the module is in an abnormal state, SIM900 can be restarted by pulling the RESET pin to ground for a typical 50uS. Reset is a noise sensitivity pin, it should be kept away from the high speed signal line (eg. clock) when layout. This pin is internal pull up to 2.8V through a 100k resistor. So it’s not necessary to add an external pull up resistor for stable consideration if it is not used. Please pay attention that reset is only used in emergency situation, such as software break down, module does not response the AT command. Reset the module continually is not recommended and it may cause some unexpected fault
see page 5 of sim900 reference design for further detail