Sample code for the MMA7660FCR1 Accelerometer Breakout Board

TAUTIC Accelerometer break out demo code.

// MMA7660FC Basic demo by Addidis  
// Released under the Creative Commons Attribution-ShareAlike License (3.0)
// http://creativecommons.org/licenses/by-sa/3.0/us/
// 10/24/11 
// HW : Tautic accelerometer board +4.7k pull ups on sda scl , uno32, led +330 resistor 
// SCL -->A5
// SDA -->A4
// INT -->D7
// gnd -->gnd
// vdd -->3.3v  NOTE 3.3v!
// LED short pin to 330 resistor to gnd
// led long pin to D6
// Open the serial monitor after running , set to 38400

// It will fire an interrupt and light the led briefly when it detects a change in orientation
// The values of the variables that are displayed are in the datasheet with what they mean. 
// See http://www.freescale.com/files/sensors/doc/data_sheet/MMA7660FC.pdf
// See Also http://store.tautic.com/mma7660fc-3-axis-1-5g-accelerometer-breakout-board.html
// See also http://i280.photobucket.com/albums/kk184/xsavior38/acceldemo.jpg

//** Includes *************************************************************************
#include <Wire.h>


//** Variables ************************************************************************
int accelintpin = 7;
int ledpin = 6;
volatile int state = 0;
volatile int led = 0;


void setup()
  {
   pinMode(ledpin, OUTPUT);
   digitalWrite(ledpin, LOW);
   pinMode(accelintpin, INPUT);
   attachInterrupt(2,accelISR, FALLING);
   Serial.begin(38400); // start serial for output
   delay(10);
   Wire.begin();   
  }

void accelISR(void)
  {
   digitalWrite(ledpin, HIGH);
   state=1;      
  }
  

void loop()
  { 
  Wire.beginTransmission(0x4C); //Set MMA7660FCR1 to active mode
  Wire.send(0x06);              //write to register 6
  Wire.send(0x03);              //turn on orientation interupt 
  Wire.send(0x01);              //set to active mode 
  Wire.send(0x00);              //clear register 8 
  Wire.endTransmission();
  delay(100);
 
  volatile signed char xneg,yneg,zneg, x,xout, y,yout, z,zout, pola,bafro,t,tilt, srst, spcnt, intsu, mode, sr, pdet, pd, shake, tilterror, tap,  face;
  while(1)
   {
   xneg=' ';    //clear bit
   yneg=' ';    //clear bit
   zneg=' ';    //clear bit
   
   if (state ==1)              //This if loop services the led. If you enable interrupts it will turn on the led
      {                          //this will turn it off after X delay.
      delay(500);
      digitalWrite(ledpin, LOW);
      state=0;
      }
   //
   Wire.beginTransmission(0x4C);
   Wire.send(0x00); // register to read
   Wire.endTransmission();  
   Wire.requestFrom(0x4C, 11);    // read a string of bytes
   while(!Wire.available()) { }   // wait for data
   xout  = Wire.receive();
   yout  = Wire.receive();
   zout  = Wire.receive();
   tilt  = Wire.receive();
   srst  = Wire.receive();
   spcnt = Wire.receive();  
   intsu = Wire.receive();  
   mode  = Wire.receive();
   sr    = Wire.receive();  
   pdet  = Wire.receive();  
   pd    = Wire.receive();  
   //Data is not proccesed , we will parse out the stuff so it matches the data sheet for reference. 
   
   if(xout<=63)
      {
       xneg=(xout&0b00100000)+13;    //it just so happens that 32 in ASCII is the first typable character. 
       x= xout&0b00011111;              //so we can just add 13 to that and procure a minus sign when it is negative
      }                                    //and a non typable character when it is not. 
   if(yout<=63)
      {
       yneg=(yout&0b00100000)+13;
       y= yout&0b00011111;            //Here we are just stripping the empty bit 7 and error bit and  and sign bit to get our actual number. 
      }
   if(zout<=63)
      {
       zneg=(zout&0b00100000)+13; 
       z= zout&0b00011111;
      }
   bafro=tilt&0b00000011;          //some more playing with bits to extract usefull information from the byte.
   pola=(tilt&0b00011100)>>2;
   tap=(tilt&0b00100000)>>5;
   tilterror=(tilt&0b01000000)>>6;
   shake=(tilt&0b10000000)>>7;

   Serial.print("X=");
   Serial.print(xneg, BYTE);
   Serial.print(x, DEC);
   Serial.print(", Y=");
   Serial.print(yneg, BYTE);
   Serial.print(y, DEC);
   Serial.print(", Z=");
   Serial.print(zneg, BYTE);
   Serial.print(z, DEC);
   Serial.print(", bafro=");
   Serial.print(bafro,BIN);
   Serial.print(", pola=");
   Serial.print(pola,BIN);
   Serial.print(", tap=");
   Serial.print(tap,DEC);
   Serial.print(", shake=");
   Serial.print(shake,DEC);
   Serial.print(", sample rate=");
   Serial.print(srst,DEC);
   Serial.print(", interrupt=");
   Serial.print(intsu,BIN);
   //todo add tap and tap debounce read out. 
   Serial.println(".");

   delay(100);
 }
}