AVR-USB-PPM/USBPPM.ino

#include "UsbJoystick.h"
#include "PPM.h"

#define CHANNELS 8
// D3 / PD3 / INT1 for PPM input
// D2 / PD2 / INT0 used for D+ of USB
// D4 / PD4 used for D- of USB

unsigned short a2dValue;
unsigned char high;
unsigned char low;
unsigned char temp;
unsigned char report[8];

void setup(void) {
  //Serial.begin(115200);
  //Serial.println("Init");
  
  ppm.begin(CHANNELS);
  usbDeviceConnect();
}

void loop(void) {
  UsbJoystick.refresh(); // Let the AVRUSB driver do some houskeeping
  calculateReport(); // Jump to our port read routine that orders the values
  UsbJoystick.sendJoystick(report[0],report[1],report[2],report[3],report[4],report[5],report[6],report[7]); // send the values
}

void calculateReport() {  //The values read from the analog ports have to be ordered in a way the HID protocol wants it; a bit confusing.
  if(!ppm.available()) {
    //Serial.println("abort");
    return;
  }

  /*
  Serial.print(ppm.get(0) - MIN_PULSE);
  Serial.print(' ');
  Serial.print(ppm.get(1) - MIN_PULSE);
  Serial.print(' ');
  Serial.print(ppm.get(2) - MIN_PULSE);
  Serial.println();
  */
  
  a2dValue = ppm.get(1) - MIN_PULSE;
  high = a2dValue >> 8;
  low = a2dValue & 255;
  report[0] = low;
  temp = high;

  a2dValue = ppm.get(0) - MIN_PULSE;
  high = a2dValue >> 6;
  low = a2dValue & 63;
  report[1] = (low << 2) + temp;
  temp = high;

  a2dValue = ppm.get(2) - MIN_PULSE;
  high = a2dValue >> 4;
  low = a2dValue & 15;
  report[2] = (low << 4) + temp;
  temp = high;

  a2dValue = ppm.get(3) - MIN_PULSE;
  high = a2dValue >> 2;
  low = a2dValue & 3;
  report[3] = (low << 6) + temp;
  temp = high;

  high = 0;
  low = 0;
  report[4] = temp;
  temp = high;

  a2dValue = ppm.get(4) - MIN_PULSE;
  high = a2dValue >> 8;
  low = a2dValue & 255;
  report[5] = low + temp;
  temp = high;

  a2dValue = ppm.get(5) - MIN_PULSE;
  high = a2dValue >> 6;
  low = a2dValue & 63;
  report[6] = (low << 2) + temp;
  temp = high;

  // 4 buttons , tossed around

  report[7] = (temp & 15);

}