Two arduinos - One BT module


is it possible to connect one HC-05 module on two arduinos (connecting TX and RX from BT module to RX and TX from both arduinos) and make it to work at the same time?

It seems to me that it will not be a problem, but I can't try this because I'm waiting for my second Nano to arrive...
Theoretically, I will send data to both Arduinos, but in their coding I will decide witch one will respond... Right?

Thanks in advance!

In theory as long as both Arduinos do not try to transmit data at the same time no bus-contention should result and things should operate as you are thinking.

Not sure how much the non-transmitting Arduino will enjoy having it’s TX line yanked around by the other Arduino though…

AFAIK you will have a problem joining the two Tx lines because the Serial system idles HIGH. You will need some method to prevent the idle from Arduino A interfering the Tx from Arduino B and vice versa.

I think it may be sufficient to put a diode at each Arduino Tx arranged so it will not pass the HIGH signal. Then on the Bluetooth side of the diodes have single pullup resisitor. However other people may have better advice.


You might get some more useful help if you explain why you need to do this.

Maybe you can also use a non-inverting buffer instead of a diode to avoid the presence of Tx signals appearing on the Tx pins of the two Arduino boards.

Can you not just have one arduino as a master, one as a slave, and have master forward to slave anything it receives?

More to the point, or maybe just better expression of the bleeding obvious, the original post shows a Nano and a Mega. The latter has extra hardware serial ports and could simply have one for bluetooth and another for Nano. It could thereby handle Nano's traffic in either direction for bluetooth as well as any of its own. It is not a matter of master and slave. A similar arrangement could be made with other Arduinos using software serial.