At most how many bluetooth modules(HC-05) can be interfaced to Arduino UNO?


Two. One on the hardware UART (TX/RX pins with the Serial object). One on SoftwareSerial on any two pins you choose.

Any more than that and you will need more hardware UARTs.

  • 1
    You can create as many SoftwareSerial objects as you like, with a BT module on each, within memory, pin, and power constraints. But only one SoftwareSerial object can be listening at a time, which may make any others less than useful.
    – JRobert
    Dec 26 '16 at 19:10
  • Also while you are sending on one reception is completely disabled (interrupts disabled) so you can only use one at once. As a rule of thumb, while you can define more than one SoftwareSerial you can only really use one of them. Personally I never even use one. I pick hardware that has enough hardware UARTs to do the job at hand.
    – Majenko
    Dec 26 '16 at 19:12

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