R/C 12-channel CPPM Solution for Pixhawk, APM, Controllers

I have many R/C planes and copters that use Frsky receivers, all operated with one radio transmitter. In some cases, I needed a solution that supports more than 8 channels, however, I wanted to continue using the same radio transmitter that I love along with the CPPM receivers installed on the other planes and drones. Unfortunately, there was no available solution that fit these needs. As a veteran hardware and software engineer (30+ years), I decided to create my own.

PPM Merger is the perfect way to upgrade your transmitter/receivers to 12 channel PPM!

It is now available on eBay (search “PPM Merger” or “12 channels CPPM solution”).

The document in the below link thoroughly describes the product and how to upgrade and set your radio controller with connection diagrams, as well as a few flight controller setting examples.
PPM Merger Documentation

Please share your comments and ideas!

Product Description
• The PPM Merger cascades two 8 channel receiver’s PPM streams (PPM1-IN and PPM2-IN) and generates a single 12-channel PPM stream of 32.5 mSec frame length through the PPM-OUT (PPM can support up to 12 channels).
• The PPM-OUT is a clone of the input streams in the appropriate order; PPM1-IN channels 1-8 followed by PPM2-IN channels 1-4.
• In addition, the left over PPM2-IN channels 5-7 output CH13-15, which can be used to turn ON/OFF (using relays) any device such as a camera shutter, landing gear, LED strips, etc. In total, the PPM merger supports 15 channels.
• The PPM merger also has 4 PWM ports that can be directly connected to servos (channels 9-12). These PWM signals are emitted in parallel to the PPM stream.

Using PPM Merger Provides the Following Advantages:
1, Using your standard receiver/transmitter modules (the well-known Frsky D series or similar)

2. Save flight controller UART port
Most flight controllers reserve the UART port for the S-BUS connection though there are limited UART ports. With a PPM connection, you can free the UART port for other important connections (telemetry, GPS, OSD, Radio telemetry, etc.)

3. Fit all 12 channels directly into the flight controller and leverage on flight controller capabilities to control channels 9-12 (such as gimbal servos and other transmitter switch controls). Plus, an extra 3 channels to turn ON/OFF other devices.

4. Compatibility with different brands of transmitter/receiver sets.

The picture below shows the product installed on my drone.


The PPM Merger was tested with several receiver types:

· Frsky 4Dr-II

· Frsky D8R-XP

· Different brands of PPM encoder module (convert any 8 PWM channel receivers to one CPPM signal). Check the link below for more info @ http://ardupilot.org/copter/docs/com...m-encoder.html

The PPM Merger module output stream was tested and runs smoothly with the following flight controllers:

· Pixhawk (Arducopter 3.4)

· Naze32 (Cleanflight 1.13 and Betaflight)

· SP Racing F3 (Cleanflight 1.13)

Other Technical Specifications:

PPM-OUT Frame length: 32.5 mSec
Pulses length (min/center/max): same as the input streams PPM1-IN and PPM2-IN
Supply voltage: 4-5.5V
Size W/H: 25 x 35 mm
Weight: 4 grams
PPM in sampling accuracy: 0.5 uSec
PPM out Replication accuracy: 0.5 uSec