File content as of revision 1:e41af8c958b8:

//AccelerometerTest
//Toby Galal
//6 November 2015
//A program used to gather data from ADXL335 accelerometers and print them to file (.txt) in a MatLab-compliant format

#include "mbed.h"

//Hardware Initialisation
AnalogIn XIn(p15); //X Input
AnalogIn YIn(p16); //Y Input
AnalogIn ZIn(p17); //Z Input
Serial pc(USBTX, USBRX); //Serial to print readings to terminal
Ticker timer; //Timer to call ISR
LocalFileSystem local("local"); // create local filesystem
BusOut leds(LED4,LED3,LED2,LED1); //debugio

//Global Variables
float XOut, YOut, ZOut; //variables to store XYZ readings
float Xo, Yo, Zo; //variables to store 0G bias readings
int flag; //flag for ISR
float X[2000], Y[2000], Z[2000]; //arrays to store results
float CalX[20], CalY[20], CalZ[20]; //arrays to store calibration readings
int n; //variable to store the number of readings

//Function Prototypes
void Calibrate();
void ISR();
void Send_Data();
void writeDataToFile();

//Main Function    
int main() {
    
    wait(5.0); //allow accelerometer to stabilise
    Calibrate();
    pc.printf("Ready in:");
    for (int i = 10; i > 0; i--) {
        pc.printf("%d\n\r", i);
        wait(1.0);
    }
    
    timer.attach(&ISR, 0.005); //attach ISR function to timer (100Hz)
    
    while (n < 2000) {
        if (flag) { //if flag has been set
            flag = 0; //reset flag
            Send_Data();
        }
    }
    pc.printf("Writing...\n\r");
    writeDataToFile();
    pc.printf("Done.\n\r");
}

//Function Definitions
void Calibrate() {
    
    for (int i = 0; i < 20; i++) { //read and store 20 samples
        CalX[i] = XIn.read() * 3.3;
        CalY[i] = YIn.read() * 3.3;
        CalZ[i] = ZIn.read() * 3.3;
    }
    
    for (int i = 0; i < 20; i++) { //sum readings
        Xo = Xo + CalX[i];
        Yo = Yo + CalY[i];
        Zo = Zo + CalZ[i];
    }
        
        Xo = Xo / 20; //find mean and store it
        Yo = Yo / 20;
        Zo = Zo / 20;
        
        pc.printf("Calibration Values = %.3f | %.3f | %.3f\n\r", Xo, Yo, Zo);
}

void ISR() {
    flag = 1;
}

void Send_Data() {
    XOut = (XIn.read() * 3.3) - Xo; //differences
    YOut = (YIn.read() * 3.3) - Yo;
    ZOut = (ZIn.read() * 3.3) - Zo;
    X[n] = XOut / 0.3; //convert voltage to g-force (300mv/g) and store in array
    Y[n] = YOut / 0.3;
    Z[n] = ZOut / 0.3;
    n++;
        
   pc.printf("%d) X = %.2f | Y = %.2f | Z = %.2f\n\r", n, XOut, YOut, ZOut);
}

void writeDataToFile() {
 
    leds = 15; // turn on LEDs for feedback
    FILE *results = fopen("/local/results.txt", "w"); // open 'results.txt' for writing
   
    fprintf(results, "x = ["); //print X array
    
    for (int i = 0; i < 1999; i++) {
        fprintf(results, "%.3f,", X[i]);
    }
    
    fprintf(results, "%.3f]\n\r", X[1999]);
    
    fprintf(results, "y = ["); //print Y array
    
    for (int i = 0; i < 1999; i++) {
        fprintf(results, "%.3f,", Y[i]);
    }
    
    fprintf(results, "%.3f]\n\r", Y[1999]);
    
    fprintf(results, "z = ["); //print Z array
    
    for (int i = 0; i < 1999; i++) {
        fprintf(results, "%.3f,", Z[i]);
    }
    
    fprintf(results, "%.3f]\n\r", Z[1999]);
     
    fclose(results); // close file
    leds = 0; // turn off LEDs to signify file access has finished
}