firmata, ping sensor, arduino, and OF problem

Forum 2005-2010 (read only) Software Interfacing
#1

I am coming from Pure Data where I had a ping sensor sending the distance in inches to Pure Data that used the distance information to play a video and different speeds.

I’d like to do the same in OF because OF handles video better.

I am getting hung up on getting the arduino to send the distance information to OF. The distance in inches should show up in the serial monitor of the arduino software, but I just get jumble data.

Here is the code I have on the arduino (.pde file):

#include <Firmata.h>

byte digitalPin;
char firstChar; 
char secondChar;
int pingPin = 7;

void digitalWriteCallback(byte pin, int value)
{
    pinMode(pin,OUTPUT);
    analogWrite(pin, value);
}

void setup()
{
    Firmata.setFirmwareVersion(0, 1);
    Firmata.attach(ANALOG_MESSAGE, digitalWriteCallback);
    Firmata.begin();
}

void loop()
{
    while(Firmata.available()) {
        Firmata.processInput();
    }
    for(digitalPin = 0; digitalPin < TOTAL_DIGITAL_PINS; digitalPin++) {
      if(digitalPin == 7)  
        Firmata.sendDigitalPort(digitalPin, computeDistance()); 
    }
}

long computeDistance(){
 long duration, inches, cm;
   // The PING))) is triggered by a HIGH pulse of 2 or more microseconds.
  // We give a short LOW pulse beforehand to ensure a clean HIGH pulse.
  pinMode(pingPin, OUTPUT);
  digitalWrite(pingPin, LOW);
  delayMicroseconds(2);
  digitalWrite(pingPin, HIGH);
  delayMicroseconds(5);
  digitalWrite(pingPin, LOW);

  // The same pin is used to read the signal from the PING))): a HIGH
  // pulse whose duration is the time (in microseconds) from the sending
  // of the ping to the reception of its echo off of an object.
  pinMode(pingPin, INPUT);
  duration = pulseIn(pingPin, HIGH);

  // convert the time into a distance
  return microsecondsToInches(duration);
  //cm = microsecondsToCentimeters(duration);
  
}

long microsecondsToInches(long microseconds)
{
  // According to Parallax's datasheet for the PING))), there are
  // 73.746 microseconds per inch (i.e. sound travels at 1130 feet per
  // second).  This gives the distance travelled by the ping, outbound
  // and return, so we divide by 2 to get the distance of the obstacle.
  return microseconds / 74 / 2;
}

long microsecondsToCentimeters(long microseconds)
{
  // The speed of sound is 340 m/s or 29 microseconds per centimeter.
  // The ping travels out and back, so to find the distance of the
  // object we take half of the distance travelled.
  return microseconds / 29 / 2;
}

Once I get the distance data to show up in the serial monitor with firmata, I will move on to getting OF to read the data.

I have scoured the internet for examples but they all deal with analog data. The ping sensor is digital so I need to be able to receive digital data in OF…

Any insights would be greatly appreciated!!

Thanks
Tim

#2