How to hack the PPM signal from any receiver (Futaba) with Arduino


Intercept the PPM signal is the best way to obtain all the channels from any receiver, for a lot of reasons. The first one is performance, and the second is the simplicity (in code =P). This hack is based on this tutorial from Paparazzi Autopilot.

For more information about the PPM frames click here.

For this hack i'm using a Futaba receiver FP-R127DF. Almost all the Futaba receivers came with the BU4015BF Shift Register chip, if your are able to locate this chip, you just need to solder a single wire in the pin 1 or 9 (clock), and you are done!
Here is the Data Sheet of the IC:BU4015.pdf

Another good way to find the PPM signal pin is using this code with arduino:

void setup()
{
Serial.begin(57600);
pinMode(3, INPUT);
}
void loop()
{
Serial.println(pulseIn(3, LOW));
}


Then upload the code to arduino, and with a wire connected to the pin 3, start touching all the pins and spots you can of you receiver (don't forget to also connect ground to ground), until you see random values between 300 to 9000 on arduino terminal (that means you found it).

After that, just solder a wire on it and use this code to decode all the channels:

#define channumber 4 //How many channels have your radio?
int value[channumber];

void setup()
{
Serial.begin(57600); //Serial Begin
pinMode(3, INPUT); //Pin 3 as input
}
void loop()
{
while(pulseIn(3, LOW) < 5000){} //Wait for the beginning of the frame
for(int x=0; x<=channumber-1; x++)//Loop to store all the channel position
{
value[x]=pulseIn(3, LOW);
}
for(int x=0; x<=channumber-1; x++)//Loop to print and clear all the channel readings
{
Serial.print(value[x]); //Print the value
Serial.print(" ");
value[x]=0; //Clear the value afeter is printed
}
Serial.println(""); //Start a new line
}


This a video where you can see everything i explained in action:

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Comment by Vernon Barry on August 17, 2012 at 5:28pm

First I said no, most Spektrum receivers do not have a sum output that is accessible.

Actually, I take that back, the Specktrum remote diversity module can be used, but only with a level shifter and a different firmware. Point being, I don't think it has been ported to APM 2.0 or 2.5 for a number of reasons http://diydrones.com/forum/topics/getting-the-ppm-encoder-working-h...

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