Alphasense.cpp

00001 #include "Alphasense.h"
00002 #include "Adafruit_ADS1015.h"
00003 
00004 ALPHASENSE::ALPHASENSE(I2C* i2c, int num_chan_op1, int num_chan_op2, int we0, int ae0, int sensitivity, int n_sample) : _i2c(i2c), _num_chan_op1(num_chan_op1), _num_chan_op2(num_chan_op2), _we0(we0), _ae0(ae0), _sensitivity(sensitivity), _n_sample(n_sample) {   
00005 }
00006 
00007 float ALPHASENSE::measure() {
00008     double we_result, ae_result;
00009     float result;
00010     int we, ae, we_integral, ae_integral;
00011     
00012     Adafruit_ADS1115 ads(_i2c); //init ads1115
00013     ads.setGain(GAIN_TWO); //set range to 2.048 V
00014     
00015     for (int i=0; i<_n_sample; i++)
00016     {
00017         we = ads.readADC_SingleEnded(_num_chan_op1); // read channel
00018         ae = ads.readADC_SingleEnded(_num_chan_op2);
00019         we_integral += we;
00020         ae_integral += ae;
00021     }
00022 
00023     we_result = we_integral / _n_sample; //smoothing result
00024     ae_result = ae_integral / _n_sample;
00025     
00026     we_result = we_result * 0.0625; //conversion to mV (2048 / 65536)
00027     ae_result = ae_result * 0.0625;
00028     
00029     we_integral = 0; //reset integral
00030     ae_integral = 0;
00031     
00032     result = (((we_result - _we0) - (ae_result - _ae0)) / _sensitivity) * 1000; //conversion to ppb
00033 
00034     return result;
00035 }