DIY Bluetooth Telemetry Bridge for Pixhawk or APM

I am using my HK Pilot32 (Pixhawk) since last year with my phone and DroidPlanner 2(now Tower). I have tested it as well with one HC-05 Bluetooth module as with 433Mhz Telemetry module. Using it with the Bluetooth module I don’t need to attach anything to my smartphone. But with the 433Mhz I have much better range. How can I get the great range without attaching something to the phone? Idea: using the 433Mhz telemetry module to transmit the data from the Pixhawk to the Bluetooth module and this one to my phone. Well I was not the first one with this idea, and I find a Bluetooth telemetry bridge from Event38. Looks good but the 150$ price is just too much in my opinion. So I decided to stick with my idea and made it by myself.

Parts needed:

Both the HC-05 Bluetooth module and the HM-TRP 433Mhz module work on 3.3V. But to use these with simple small 3.7V LiPo Battery, we need not the bare HC-05 Module. Take the one with integrated voltage regulator and pins already soldered (like the second or third one on the picture below).


If you already have a 433Mhz Kit from 3DRobotics or HobbyKing you need to unsolder the HM-TRP module from the receiver module (the one with the USB Plug). Or as said you can buy only the bare HM-TRP module from Aliexpress. Download the datasheet for the module to check how it looks like and the pins descriptions.

What we need to do:

First both modules should use the same baud rate for communication. The standard for the 3DR Robotics module is 57600. So we need to change the baud rate for the Bluetooth module to be the same. You can check how to do this here.

Then take the 4 tiny cables and solder the pins from the HM-TRP module to the pins of the Bluetooth module as described:

  • 5V HM-TRP Module – 5V Bluetooth Module (before last Pin on the left side)
  • GND HM-TRP Module – GND Bluetooth Module (last Pin on the left side)
  • TX HM-TRP Module – RX Bluetooth Module (2 Pin on the left side)
  • RX HM-TRP Module – TX Bluetooth Module (1 Pin on the left side)


A bit tricky was to solder the antenna to the tiny module. First you need to remove the plastic black cover. Cut the coax cable and remove the PVC shield. Then take the metal shielding and without cutting it, form it as a cable and solder it to the GND Pin of the HM-TRP module. The tiny cable under the shielding layer is the cable for the Antenna. Solder this one to the ANT Pin of the HM-TRP module.

That is all!

I used hot glue to place the HM-TRP 433Mhz module on the backside of the Bluetooth module, so it looks better and its more compact. Now you can connect the pins of the Bluetooth module to the battery and have your own Bluetooth Telemetry Bridge.