Hello, dear colleagues!

Just a couple of days ago I did a little upgrade to my 250-size copter. I decided to supplement it with a sonar and a GPS receiver. However, I realized that the Naze32 flight controller had too few unoccupied legs, when I was connecting the receiver in parallel-PWM mode… That was hardly a big issue, and it could be solved easily by installing a PPM-Sum module. AliExpress and other stores are crowded with them, but waiting another month did not sound like an attractive option to me, and the all-go-know Google suggested that it could be made of an Arduino (which I had galore) by way of a few simple soldering manipulations...
I found an article on the subject (why reinvent the wheel). The Arduino IDE sketch struck me as concise and laconic – brevity is everything. Yes, it is! However, as to the PPM-sum module’s appearance, it looked less inspiring to me… Finally, I decided to build a universal ParallelPPM/PPMSum receiver, which would be wholly placed in a Turnigy 9X8Cv2 frame.

To carry out the set task, I took an Arduino Pro Mini using the sketch, which you can see at the bottom of the page. I didn’t solder leads to the module when flashing it (because otherwise they would get in the way pretty much) and inserted a comb, which was included in the pack, at the side of the BLK-GND-VCC-RX1-TX0, and connected them to respective USB-COM ports of the receiver and uploaded the sketch into the board…

Next I soldered 8 wire output channel leads of the receiver to the Ardudino board (see the table below):


I recommend thinner wires, so that you can fit them in the receiver. I used fragments of an old unused VGA cable, which had consisted of different wires, including a couple of thin multicore ones.

I powered the Arduino board from the receiver’s +5V and GND control channels (the thin black and red wires in the photo below). ATTENTION!!! Dear colleagues! Please, be careful when soldering power wires. Improper polarity will destroy your Ardino and, possibly, the power supply.

To make a PPMSum connector, I took a servo connector and removed the plastic frame from it. Then I pulled out the two wires, which I had bought for the Breadboard.


Here is the result:

I glued the newly-made connector to the component-free side of the receiver board with cyanoacrylate.

To prevent a short-circuit I covered one side of the Arduino board with black tape. I made the strip was a bit longer than the board, so I bent the ends around the edges (also for isolation purposes).

I cut a square hollow in the frame for the mating PPMSum connector with a needle file. There had been two protruding fixing bumps on the flame’s cover, which I had to cut off. Which ones you want to cut off depends on where you want to place your Arduino board.


In order to distinguish between the PPMSum outputs, I glued a piece of paper onto the cover and marked the outputs. Because the cover is made of translucent plastic, I marked the inner side with pieces of adhesive tape.

Put everything inside, close the cover and fix it with screws.

Now we have a n 8-channel Turnigy9X8C V2, which can operate in both ParallelPWM and PPMSum mode.

This technique was successfully tested on my copter’s Naze32 flight controller flashed with CleanFlight 1.12.0. However, there is something you should note: the controller adds 1 to each channel, i. e. it recognizes CH1 as CH2, CH2 as CH3, and CH1 is always tuned to zero… This can be solved by shifting all channels by 1 point with the mixer (my transmitter is flashed with Er9X, I have no idea how to do it with the stock firmware installed, because I’ve never used it)


References:

1. You can buy Arduino Pro Mini here. That is no big problem: all you need to do is open AliExpress, type in Arduino Pro Mini and select from the huge number of alternatives.

2. Wires for PPMSum connection. Look i the same place as the previous item.

3. Arduino Pro Mini sketch ppmsum.ino

I’m not sure if this article is really good, but if at least one person finds it helpful, it won’t be a waste of time.

Good luck!

"Let it be, let it be, there will be good fortune, let it be!"
This is the translated version. You can read the original Russian article here.