Waiting for RDY is not possible if Auto-Bauding is enabled

[Technohacker]

arduino-sim808/src/SIM808.cpp

Lines 53 to 54 in a0b3dcd

	// we got AT, waiting for RDY
	while (waitResponse(TO_F(TOKEN_RDY)) != 0);

As per the SIM808 manual:

When power on procedure is completed, SIM808 will send following URC to indicate that the module is ready to operate at fixed baud rate.

RDY

This URC does not appear when autobauding function is active.
Note: User can use AT command “AT+IPR=x” to set a fixed baud rate and save the configuration to non-volatile flash memory. After the configuration is saved as fixed baud rate, the Code “RDY” should be received from the serial port every time when SIM808 is powered on. For details, please refer to the chapter “AT+IPR” in document [1].

Unfortunately in the breakout board I have available, AT+IPR does not preserve its value (likely due to missing flash storage). It may make sense to only use the AT -> OK response for such situations