I have an ADH8066 GSM module that I'm trying to get up and running. I'm powering it with 4V (via a 2A adjustable regulator), and I'm using a Bus Pirate connected to its RX0 and TX0 lines. I'm not using RTS/DSR/CTS, because the datasheet says it doesn't do flow control by default. I do have a SIM card installed, but it's a non-activated one. I don't expect that to make a difference to whether or not the UART interface is available.

I'm pulling ONKEY low for about 2 seconds to turn it on. It's powering up, and I get the following output:

IIII
SystemInit



However, it doesn't seem to accept any input. I believe that remote echo is turned on by default, but I get nothing echoed back to me. AT does not result in OK, and no other informational command gives me any output. I've sent commands with explicit "AT+CGMM" 13 10 to ensure the line ending is correct.

During all this, GPIO10 (ready for AT command) remains low. The datasheet doesn't say which state is active, but I'm assuming active high based on some people's LED wiring.

Is there something else I'm not doing?

There are a few suggestions I can think of, the first is to try sending a few CR/LF pairs at startup followed by the ATE1Q0 and see what that does. The power-up defaults don't seem to be explicitly stated in the datasheet but some GSM modules startup in quiet mode and won't respond to AT with an OK response.