ADXL345.cpp

00001 #include "ADXL345.h"
00002 
00003 ADXL345::ADXL345(PinName sda, PinName scl) : I2C_Sensor(sda, scl, ADXL345_I2C_ADDRESS)
00004 {
00005     // Set Offset  - programmed into the OFSX, OFSY, and OFXZ registers, respectively, as 0xFD, 0x03 and 0xFE.
00006     writeRegister(ADXL345_OFSX_REG, 0xFA); // to get these offsets just lie your sensor down on the table always the axis pointing down to earth has 200+ and the others should have more or less 0
00007     writeRegister(ADXL345_OFSY_REG, 0xFE);
00008     writeRegister(ADXL345_OFSZ_REG, 0x0A);
00009  
00010     writeRegister(ADXL345_BW_RATE_REG, 0x0F); // 3200Hz BW-Rate
00011     writeRegister(ADXL345_DATA_FORMAT_REG, 0x0B); // set data format to full resolution and +-16g
00012     writeRegister(ADXL345_POWER_CTL_REG, 0x08); // set mode
00013 }
00014 
00015 void ADXL345::read(){
00016     readraw();
00017     for (int i = 0; i < 3; i++)
00018         data[i] = raw[i] - offset[i]; // TODO: didnt care about units 
00019 }
00020 
00021 void ADXL345::readraw(){
00022     char buffer[6];    
00023     readMultiRegister(ADXL345_DATAX0_REG, buffer, 6);
00024     
00025     raw[0] = (short) ((int)buffer[1] << 8 | (int)buffer[0]);
00026     raw[1] = (short) ((int)buffer[3] << 8 | (int)buffer[2]);
00027     raw[2] = (short) ((int)buffer[5] << 8 | (int)buffer[4]);
00028 }
00029 
00030 void ADXL345::calibrate(int times, float separation_time)
00031 {
00032     // calibrate sensor with an average of count samples (result of calibration stored in offset[])
00033     float calib[3] = {0,0,0};                           // temporary array for the sum of calibration measurement
00034     
00035     for (int i = 0; i < times; i++) {                   // read 'times' times the data in a very short time
00036         readraw();
00037         for (int j = 0; j < 3; j++)
00038             calib[j] += raw[j];
00039         wait(separation_time);
00040     }
00041     
00042     for (int i = 0; i < 2; i++)
00043         offset[i] = calib[i]/times;                     // take the average of the calibration measurements
00044 }