SIM800 AT Module Help

I was working with a SIM900 module and using the espruino SIM900 module. I had problems so we ended up purchasing a SIM800 module.

The SIM900 espruino code module was just hanging forever on the first simple ATE0 command. So to test I just tried to use the AT espruino code module directly to connect to the SIM800 and try to issue an AT command... hangs forever. I even tried a very long timeout of 10s to try to see if that was the problem.

What am I doing wrong here? (I also pulled the AT code locally and tried to put in some debug bug got nowhere because i never get the on data callback to fire on the serial connection.) This exact code works find if I plug it into my sim900 chip.

Serial3.setup(115200, { rx: B11, tx : B10 });
var at = require('AT').connect(Serial3);
setTimeout(function(){
  at.debug();
  at.cmd('AT\r\n', 10000, function(r){
    console.log(r);
  });
    
    
}, 10000);

What is the reason that you do not let Espruino control the reset of the SIM module?

It could well be that the power-on sequence is not yielding the proper reset / initialization sequence. Note that Espruino's SIM900 sw module expects the reset pin as 2nd argument.

The SIM900 module I have actually does not have a reset pin unfortunately. Also, the SIM800 is said to have a lower power consumption. We just bought a newer SIM800 we are going to try when it comes in - we read something about the SIM800 wanting 2.8V on the RX side but the new one we bought said it has level shifting circuitry to support 2.8-5V logic. I'll come back here with my findings from the newer SIM800 when it comes in.

It sounds a bit like you're just not getting any characters back from the module at all?

Could it be a baud rate or wiring issue? Or perhaps the board needs some pin pulled up/down in order to turn on?