RC Receiver Hacking Tutorial

In some RC homemade applications based on microcontrollers, the receiver must be slightly modified in order to get a PPM signal.


Let's see how to patch a Castle Creations Berg 4L RC receiver...


Tools & Materials

For this mission, you need:

  • Knife with good blade
  • Small wire cutters
  • Soldering Iron and soldering wire
  • Heatshrink (to wrap your receiver)
  • RC Transmitter (!) and matching receiver crystal
  • red, black and third color small wire

Optional but useful:

  • Tweezers
  • Oscilloscope + Probe (if the PPM signal location is unknown)
  • Band-Aid Complice

Stage 1: Remove the shrink wrap

Fortunately the first stage is the easyest one.

  • Remove the heatshrink cover carefully with a good RC modelling knife.

    Be careful to not damage the shieldind or any other component.


Stage 2 (optional): Remove servo header

This stage is useful only if original servo signal are unused and mass saving is needed.

  • disolder carefully the piece of shielding connected to one of the ground pin of the servo header.


  • Cut the top row header pins off and remove it one by one with the soldering iron.


  • Cut the second row header pins off and disolder it


  • Re-solder the piece of shielding on a ground pad


Stage 3: Install Power Supply Wires

  • On the servo header pads, locate (+) and (-) and solder your cables.
    Note : (+) is always servo connector center pin, and original sticker on the heatshrink wrap can help.


Stage 4: Locate PPM Signal

This stage is the hardest one, the best way to achieve is to use an oscilloscope (or look if your receiver model appears in the RC Receiver hacked article.)

  • Plug a crystal in the receiver
  • Connect the receiver to a 5v power supply
  • Turn on your RC transmitter (check if the transmitter/receiver frequencies are matching)
  • With the oscilloscope probe, try to locate a signal like on the screenshot below.
    Often, the PPM signal can be found on an integrated circuit connected directly to the servo header pads (PPM decoder)
    Note : if your transmitter is N channel, you should count N+1 pulses in the PPM frame, regardless of the receiver channel number




  • solder carrefully the PPM signal cable


Stage 5: Finishing

  • Wrap the receiver with a nice peace of heatshrink




  • install the 3 pin connector



Done... !


Other Hacked Receivers

Click here to see other brand and model RC receivers hacking...