Help with bluetooth module for 3pi

Hi, I’m trying to set up this project:
though for the moment I’m just focusing on the remote control via bluetooth, so I don’t have a range sensor or rgb leds.

I have this Bluetooth module: … -42-module

I can connect to it and pair with it from Android, but when I hook it up to my 3pi and use the Android lightRobot control app, nothing happens.

The module requires 3.3V, and as far as I know, the 3pi only outputs 5v, unlike the Arduino. So I am powering the bluetooth module with two AAA batteries connected to the bluetooth VCC and GND pins, but I am running the RX and TX pins to the 3pi PD0 and PD1 pins. Is this setup likely to be a possible cause of the problems I’m having? If so, what would be a better arrangement?



Since we do not carry this bluetooth module, we can only offer limited assistance with getting it working with your 3pi Robot. However, here are some common issues that might help you out. Since your bluetooth module does not appear to be 5V tolerant, you should use a voltage divider between the 3pi TX pin and the modules RX pin to prevent damage to the bluetooth module. The 3pi should be able to read the 3.3V output of the bluetooth module. The bluetooth module appears to have a built-in voltage regulator that can handle up to 16V, so you might not need to power it from a separate source (and two AAA batteries are likely not an appropriate power supply). You should be sure both units share a common ground, so powering them from the same source might make the most sense. If you do use separate power sources, be sure to connect the grounds together in some way.


Hi Derrill,
That’s really useful, thanks. I’ll post an update with more details if I get it working.

Hi again,
The problem was the 5v going into the bluetooth module’s RX pin. I made a simple voltage divider circuit to attenuate that to 3.3v (see here: and the module started responding as expected. (I notice that others say a regulator is a better idea than a resistor circuit like this.)
I am also powering the bluetooth module from the 3pi instead of the batteries - that works.
Thanks for the help!

Thank you for posting what the problem was and the solution that worked for you.