Reply To: Two Unos over a pair of HC-05s so the one with the GSM modem reports both

Posted October 29, 2026 at 4:47 pm #3

I did exactly this for a uni lab last term and got the same ERROR on BIND. The address comes out of AT+ADDR? with colons, but AT+BIND wants commas, in the order NAP,UAP,LAP:

AT+BIND=98d3,31,fb1234

Full sequence that worked for us, both modules entered with KEY/EN held high at power-up (AT mode is 38400 baud):

slave A:  AT+ORGL
          AT+ROLE=0
          AT+PSWD="4321"
          AT+UART=9600,0,0

master B: AT+ORGL
          AT+ROLE=1
          AT+CMODE=0
          AT+PSWD="4321"
          AT+BIND=98d3,31,fb1234
          AT+UART=9600,0,0

Same PSWD on both, then power-cycle both without KEY held. Master pairs within a few seconds. After that it’s a plain 9600 serial line between the Unos.