@ziovic said in MKR1000 gateway problem: The dtostrf function included in MyHwSAMD.h is the AVR one ( avr/dtostrf.h) does not work with SAMD core. Well, this implementation is part of the official arduino Samd core: https://github.com/arduino/ArduinoCore-samd/blob/master/cores/arduino/avr/dtostrf.c You could file a bug report there if you like.