This new should create a better PPM output. I'm now working on integrating this with code from cellbots.com so that I can attach an android phone to the bot.
#include <Messenger.h>
#include
/*
* Vexduino 2.0 Interface
* -------------------
*
* 12/31/2011
* Copyleft 2011 Jeremy Espino MD
* Licensed under the the Apache 2.0 License
* espinoj@gmail.com
* vexduino.blogspot.com
* modified for vexplorer compatibility
*
*/
#define PPM_OUT_PIN 12 // which pin to output the PPM signal on
#define FRAME_LENGTH 20 // length of PPM frame in ms
#define PULSE_START 300 // pulse start width
#define PULSE_MIN 600 // pulse minimum width in microsecs
#define PULSE_MAX 1700 // pulse max width in microsecs
#define SERVO_MAX 9 // max servo value
#define SERVO_CNTR 5 // servo center value
#define CHANNEL_NUM 8 // number of channels in the PPM
// A pulse starts with a high signal of fixed width (0.3ms),
// followed by a low signal for the remainder of the pulse.
// Total pulse width is proportional to servo position (.6 to 1.7ms)
// conversion factor for servo to signal pulse width
const int conversionFactor = (PULSE_MAX - PULSE_MIN)/ SERVO_MAX;
// A frame is a succession of pulses, in order of channels,
// followed by a synchronisation pulse to fill out the frame.
// A frame's total length is fixed (20ms)
int servo[CHANNEL_NUM]; // Values to set for motor speed 0 - 9, 5 is neutral
int channel[CHANNEL_NUM]; // Channel pulse width (duration of pulse minus start, in microseconds)
int mapping[CHANNEL_NUM]; // map of vex "channel" to PPM radio channels
ISR(TIMER1_COMPA_vect) {
ppmoutput(); // Jump to ppmoutput subroutine
}
Messenger message = Messenger();
byte isAllStop = 0; // flag to set all channels to center
int inputValue; // input value from the serial
int value[CHANNEL_NUM];
// initialize servo and channel values to center points
void allStop() {
for (int i = 0; i < CHANNEL_NUM; i = i + 1 ) {
servo[i] = SERVO_CNTR;
}
for (int i = 0; i < CHANNEL_NUM; i = i + 1 ) {
channel[i] = (PULSE_MAX - PULSE_MIN) / 2;
}
}
void setupPPM() {
// Setup timer
TCCR1A = B00110001; // Compare register B used in mode '3'
TCCR1B = B00010010; // WGM13 and CS11 set to 1
TCCR1C = B00000000; // All set to 0
TIMSK1 = B00000010; // Interrupt on compare B
TIFR1 = B00000010; // Interrupt on compare B
OCR1A = 20000; // 20mS PPM output refresh
OCR1B = 1000;
// setup mapping channel to pulse sequence
mapping[6]=0;
mapping[5]=1;
mapping[4]=2;
mapping[3]=4;
mapping[2]=5;
mapping[1]=6;
pinMode(PPM_OUT_PIN, OUTPUT);
}
void setup() {
setupPPM();
// Initiate Serial Communication
Serial.begin(57600);
allStop();
Serial.println("\nVexduino Transmitter Interface ready!");
}
void ppmoutput() { // PPM output sub
// This for loop generates the pulse train
for (int i = 0; i < CHANNEL_NUM; i = i + 1 ) {
// Calculate pulse durations from servo positions
channel[i] = int(servo[i]*conversionFactor) + PULSE_MIN;
digitalWrite(PPM_OUT_PIN, HIGH); // Initiate pulse start
delayMicroseconds(PULSE_START); // Duration of pulse start
digitalWrite(PPM_OUT_PIN, LOW); // Stop pulse start
delayMicroseconds(channel[i]); // Finish off pulse
}
digitalWrite(PPM_OUT_PIN, HIGH); // Initiate synchronisation pulse
delayMicroseconds(PULSE_START); // Duration of start of synchronisation pulse
digitalWrite(PPM_OUT_PIN, LOW); // Stop synchronisation pulse start
}
void readSerialInput() {
// read the next set of servo settings from serial input
while ( Serial.available() ) {
if ( message.process(Serial.read() ) ){
int p = 1;
while( message.available() ) {
inputValue = message.readInt();
// a value of 999 indicates all stop position
if (inputValue == 999) isAllStop = 1;
servo[mapping[p]] = inputValue;
// if invalid servo position set to center
if ( servo[mapping[p]] > SERVO_MAX) servo[mapping[p]] = SERVO_CNTR;
p = p + 1;
}
if (isAllStop == 1) {
allStop();
isAllStop = 0;
}
}
}
}
void outputCurrentSettings() {
// show current settings
// skip vex "channels" 0 and 7 since they are numbered 1 thru 6
Serial.print("\r");
for (int i = 1; i < 7; i = i + 1 ) {
Serial.print(i);
Serial.print(":");
Serial.print(servo[mapping[i]]);
Serial.print(" ");
}
Serial.print(" ");
for(int x=0; x<=CHANNEL_NUM-1; x++) //Loop to print and clear all the channel readings
{
Serial.print(x);
Serial.print(":");
Serial.print(value[x]); //Print the value
Serial.print(" ");
value[x]=0; //Clear the value after is printed
}
Serial.print(" "); //Start a new line
}
void loop() {
readSerialInput();
outputCurrentSettings();
delay(10);
}
