I am using SIM 900 modem to enable GSM connection wirh my product. Micro-controller Communicates with SIM900 modem through a SET AT commands over UART. My product is time critical and i need to have updated time even after power failure. To achieve this I am using inbuilt RTC of SIM900 modem. After each power ON I send following sequence to modem:
After this I am supposed to get +PSUTTZ string from modem which has timestamp in it and it indicated that modem has synchronized its time with network.After this after this I send AT+CCLK? command periodically to modem to read its RTC.
The problem is sometimes I does receive +PSUTTZ string from modem with some Service providers. With BSNL(in India) service provider I never able to get this string.
Anyone has Idea that how to make sure that +PSUTTZ will always receive without fail? (May be some different AT commands or something?)