GPRS communication source
Xin Wang welding of hardware at first came back after missing a few capacitors and one of 100k resistance, main is the power supply capacitor energy storage function,
Sim300 100k resistance between simpress VEXT and PIN on the SIM card, no welding is when you can find the network, but will occur
NET, and after make up these, no problem. Previous experience of the circuit it is quite accurate. The power supply must be stable.
Text message as soon after the initialization is complete, the first text message failed. In serial port receive and send text messages while waiting for the module to return information,