I want my SIM800 module (I interfaced it with Arduino Uno) to enter sleepmode-2 (I used AT+CSCLK=2 command). My question is, how do I wake it up from sleep? I tried giving various AT commands but I cannot see anything on the Arduino Terminal.
According to this page, to wake it up, you need to send any AT command, which will be ignored by the module (so no response), followed (within 5 seconds) by
It took me all of one minute to find that by Googling "SIM800 sleep wake".
The second AT needs to follow the first within 50 ms. This could be AT+CSCLK=0 if you want the SIM800 to stay awake. You don't want it napping when you are waiting for it to confirm a connection. I think the DTR pin needs to be held high too and if you arrange that via a GPIO pin you can use AT+CSCLK=1.