Create MSP2PPM.ino

arduino/MSP2PPM.ino

@@ -0,0 +1,153 @@
+//////////////////////CONFIGURATION///////////////////////////////
+#define CHANNEL_NUMBER 8  //set the number of chanels
+#define CHANNEL_DEFAULT_VALUE 1200  //set the default servo value
+#define FRAME_LENGTH 22500  //set the PPM frame length in microseconds (1ms = 1000µs)
+#define PULSE_LENGTH 300  //set the pulse length
+#define onState 1  //set polarity of the pulses: 1 is positive, 0 is negative
+#define sigPin 10  //set PPM signal output pin on the arduino
+#define FAILSAFE 500 //activate failsafe after 1000ms of inactivity
+#define FAILSAFE_THROTTLE_VALUE 1350 // value we put to throttle if failsafe is activated
+
+/*this array holds the servo values for the ppm signal
+ change theese values in your code (usually servo values move between 1000 and 2000)*/
+int ppm[CHANNEL_NUMBER];
+uint8_t msp_packet[22];
+int msp_packet_index=0;
+long int last_receive;
+
+
+void setup(){  
+
+  //initiallize default ppm values
+  for(int i=0; i<CHANNEL_NUMBER; i++){
+      ppm[i]= CHANNEL_DEFAULT_VALUE;
+  }
+
+  last_receive=millis();
+  pinMode(sigPin, OUTPUT);
+  digitalWrite(sigPin, !onState);  //set the PPM signal pin to the default state (off)
+
+  Serial.begin(115200);
+
+  cli();
+  TCCR1A = 0; // set entire TCCR1 register to 0
+  TCCR1B = 0;
+
+  OCR1A = 100;  // compare match register, change this
+  TCCR1B |= (1 << WGM12);  // turn on CTC mode
+  TCCR1B |= (1 << CS11);  // 8 prescaler: 0,5 microseconds at 16mhz
+  TIMSK1 |= (1 << OCIE1A); // enable timer compare interrupt
+  sei();
+
+}
+
+
+void loop(){
+
+  uint8_t c;
+  int crc;
+  int i;
+  int channel_index;
+
+  while(Serial.available())
+  {
+    c=Serial.read();
+
+    if(msp_packet_index==0 && c!=36) // $ character
+    {
+      continue;
+    }
+
+    if(msp_packet_index==1 && c!=77) // M character
+    {
+      continue;
+    }
+
+    if(msp_packet_index==2 && c!=60) // < character
+    {
+      continue;
+    }
+
+    msp_packet[msp_packet_index]=c;
+
+    if(msp_packet_index==21) // packet complete
+    {
+      crc=0;
+
+      for(i=3;i<21;i++)
+      {
+        crc^=msp_packet[i];
+      }
+
+      //msp fame valid
+      if(crc==msp_packet[21])
+      {
+      	last_receive=millis();
+        channel_index=0;
+
+        for(channel_index=0;channel_index<CHANNEL_NUMBER;channel_index++)
+        {
+          ppm[channel_index]=(msp_packet[5+channel_index*2+1]<<8)+msp_packet[5+channel_index*2];
+         // Serial.print(channel_index);Serial.print(":");Serial.print(ppm[channel_index]);Serial.print(", ");
+        }
+
+        //Serial.println();
+      }
+      else
+      {
+        Serial.println("fi");
+      }
+
+      msp_packet_index=0;
+    }
+    else
+    {
+      msp_packet_index++;
+    }
+  }
+
+  if((millis()-last_receive)>FAILSAFE)
+  {
+  	  Serial.print(millis());Serial.print(":");Serial.println(last_receive);
+
+  	  //this will activate failsafe
+  	  ppm[2]=FAILSAFE_THROTTLE_VALUE;
+  }
+
+  /*
+    Here modify ppm array and set any channel to value between 1000 and 2000. 
+    Timer running in the background will take care of the rest and automatically 
+    generate PPM signal on output pin using values in ppm array
+  */
+
+}
+
+ISR(TIMER1_COMPA_vect){  //leave this alone
+  static boolean state = true;
+
+  TCNT1 = 0;
+
+  if (state) {  //start pulse
+    digitalWrite(sigPin, onState);
+    OCR1A = PULSE_LENGTH*2;
+    state = false;
+  } else{  //end pulse and calculate when to start the next pulse
+    static byte cur_chan_numb;
+    static unsigned int calc_rest;
+
+    digitalWrite(sigPin, !onState);
+    state = true;
+
+    if(cur_chan_numb >= CHANNEL_NUMBER){
+      cur_chan_numb = 0;
+      calc_rest = calc_rest + PULSE_LENGTH;// 
+      OCR1A = (FRAME_LENGTH - calc_rest)*2;
+      calc_rest = 0;
+    }
+    else{
+      OCR1A = (ppm[cur_chan_numb] - PULSE_LENGTH)*2;
+      calc_rest = calc_rest + ppm[cur_chan_numb];
+      cur_chan_numb++;
+    }     
+  }
+}