Hi Thorsten,
Same issue here. The example code doesn't work at all: https://github.com/m5stack/M5-ProductExampleCodes/blob/master/Module/NB_IOT/Arduino/NB_IOT.ino
Code refers pin 5 in the setup and that pin is used in the schematics for serial line receive (and actually it is not connected as zero ohm resistor is missing). I think this code is just some kind of copy other M5Stack module examples and not suitable for this.
This module seems to be dead even I try to switch on power and reset as it have been guided in their website:
Power Operation:
Power On: GPIO2 stay HIGH for 2s
Power Off: GPIO2 stay HIGH for 8s
Power On: Button long-press for 2s
Power Off: Button long-press for 8s
Reset module: GPIO26 HIGH
In code level I have used following in setup:
pinMode(2, OUTPUT);
pinMode(26, OUTPUT);
digitalWrite(2, 1);
delay(3000);
digitalWrite(2, 0);
digitalWrite(26, 0);
delay(500);
digitalWrite(26, 1);
delay(500);
digitalWrite(26, 0);
When I send AT command to module. Sometimes it reply empty characters, but I am not sure is that just a noise.
Any help is appreciated!
Best regards, Jarkko