File content as of revision 0:7e6a051d1700:

/*
 * mbed library to use a TAOS TSL2550 Ambient Light Sensor
 * Copyright (c) 2011 Stefan Goeckeritz, 
 * RheinAhrCampus Remagen, Suedallee 2, 53424 Remagen
 * 
 * Released under the MIT License: http://mbed.org/license/mit
 */

#include "mbed.h"
#include "TSL2550.h"

#define TSL2550_ADDR 0x72                                                     //hardwired slave address of TSL2550
#define xpow(x, y) ((long)1 << y)


TSL2550::TSL2550 (PinName p_sda, PinName p_scl ) : i2c(p_sda, p_scl) {
    init();
}

TSL2550::TSL2550 (I2C& p_i2c) : i2c(p_i2c) { 
    init();
}

unsigned short  TSL2550::get_ch0() {
    return ch0;
}

unsigned short TSL2550::get_ch1() {
    return ch1;
}

double TSL2550::get_lux() {
    return lux;
}

void TSL2550::update () {
    unsigned short c0, c1, s0, s1;
    int adc0, adc1;
    double r;

    //read channel 0 and 1
    ch0 = twi_read(TSL2550_ADDR, 0x43);
    wait(0.5);
    ch1 = twi_read(TSL2550_ADDR, 0x83);

    //now compute lux value, if data is valid
    if((ch0 & 0x80) &&  (ch1 & 0x80))
    {
        c0 = (ch0 & ~0x80) >> 4 ;
        c1 = (ch1 & ~0x80) >> 4 ;
        s0 = ch0 & ~0xF0 ;
        s1 = ch1 & ~0xF0 ;
                
        //ADC Count Value
        adc0 = int(16.5 * xpow(2,c0)) + (s0 * xpow(2,c0));
        adc1 = int(16.5 * xpow(2,c1)) + (s1 * xpow(2,c1));
        
        r = (double(adc1) / double(adc0));
        lux = double(adc0) * 0.46 * exp(-3.13 * r);
                
        //give debug information
        //printf("\n\nZW: c0=%i s0=%i c1=%i s1=%i \n", c0, s0, c1, s1);
        //printf("ZW: adc0=%i, adc1=%i\n", adc0, adc1);
    }
    else
        printf("TSL2550: ***data not valid ! ***\n");    
}

void TSL2550::init() {
    unsigned short i;
    
    i = twi_read(TSL2550_ADDR, 0x03);
    if( i == 0x03 )
        printf("TSL2550: Init successful\n");
    else
        printf("TSL2550: Init ***failed*** !\n");    
}

unsigned short TSL2550::twi_read (unsigned short id, unsigned short data) {
    unsigned short i;

    //supply COMMAND byte to slave
    i2c.start();
    i2c.write(id);
    i2c.write(data);

    //demand ANSWER byte from slave    
    i2c.start();
    i2c.write(id | 1);
    i = i2c.read(0);
    i2c.stop();
    

    return i;
}

void TSL2550::twi_write (unsigned short id, unsigned short data) {

    i2c.start();
    i2c.write(id);
    i2c.write(data);
    i2c.stop();
}