LPS331.cpp

00001 
00002 #include <mbed.h>
00003 #include "LPS331.h"
00004 
00005 #define STATUS_REG         0x27
00006 #define MULTI_BYTE         0x40
00007 #define REF_P_XL           0x08
00008 #define REF_P_L            0x09
00009 #define REF_P_H            0x0A
00010 #define WHO_AM_I           0x0F
00011 #define RES_CONF           0x10
00012 #define CTRL_REG1          0x20
00013 #define PRESS_POUT_XL_REH  0x28
00014 #define PRESS_OUT_L        0x29
00015 #define PRESS_OUT_H        0x2A
00016 #define TEMP_OUT_L         0x2B
00017 #define TEMP_OUT_H         0x2C
00018 
00019 #define WRITE              0x00
00020 #define READ               0x80
00021 
00022 #define pSensor            0x02
00023 #define tSensor            0x01
00024 #define bothSensors        0x03
00025 
00026 lps331::lps331(SPI& _spi, PinName _ncs) : spi(_spi), ncs(_ncs) {
00027 }
00028 
00029 uint16_t lps331::read_temperature() {
00030     // check if updated value is available
00031     if ( ready(tSensor) )
00032     {
00033         select();
00034         // do multi byte read
00035         spi.write(READ | MULTI_BYTE | TEMP_OUT_L);
00036         uint8_t tempL = spi.write(READ);
00037         uint8_t tempH = spi.write(READ);
00038         deselect();
00039         
00040         uint16_t temperature = (tempH<<8) | tempL;
00041         // t[C] = 42.5 + temperature /480.0
00042         //float temp = (float)(42.5 + ((short)temperature*1.0/480.0));
00043         return temperature;
00044     }
00045     return 0;
00046 }
00047 
00048 uint32_t lps331::read_pressure() {
00049     // check if updated value is available
00050     if ( ready(pSensor) )
00051     {
00052         select();
00053         // do multi byte read
00054         spi.write(READ | MULTI_BYTE | PRESS_POUT_XL_REH);
00055         uint8_t pressureLX = spi.write(READ);
00056         uint8_t pressureL = spi.write(READ);
00057         uint8_t pressureH = spi.write(READ);
00058         deselect();
00059         
00060         uint32_t pressure = (pressureH<<16) | (pressureL<<8) | pressureLX;
00061         // P[mBar] = pressure/4096
00062         // float P = pressure*1.0/4096.0;
00063         return pressure;
00064     }
00065     return 0;
00066 }
00067 
00068 float lps331::get_Pressure_mbar()
00069 {
00070     uint32_t airP = read_pressure();
00071     float pressure = airP*1.0/4096.0;
00072     return pressure;
00073 }
00074 
00075 float lps331::get_Temp_C()
00076 {
00077     short airT = read_temperature();
00078     float temp = (float)(42.5 + (airT*1.0/480.0));
00079     return temp;
00080 }
00081 
00082 float lps331::get_Temp_F()
00083 {
00084     short airT = read_temperature();
00085     float temp = (float)(108.5 + (airT*1.8/480.0));
00086     return temp;
00087 }
00088 
00089 void lps331::select() {
00090     //Set CS low to start transmission (interrupts conversion)
00091     ncs = 0;
00092 }
00093 
00094 void lps331::deselect() {
00095     //Set CS high to stop transmission (restarts conversion)
00096     ncs = 1;
00097 }
00098 
00099 bool lps331::initialize(int setType) {
00100     deselect();
00101     spi.format(8,0);
00102     spi.frequency(400000);  
00103     
00104     // set chip to update pressure and temp at 25Hz
00105     writeRegister(CTRL_REG1, 0xE0);
00106     wait_ms(1);
00107     
00108     // check board is responding
00109     int whoami = readRegister(WHO_AM_I);
00110     if (whoami == 0xBB)  // addresss of chip
00111         return true;
00112     return false;
00113 }
00114 
00115 int lps331::ready(uint8_t sensor) {
00116     uint8_t status = readRegister(STATUS_REG);
00117     if( (status & sensor))
00118         return 1;
00119     return 0;
00120 }
00121 
00122 uint8_t lps331::readRegister(uint8_t address){
00123     select();
00124     spi.write(READ | address);
00125     uint8_t val = spi.write(READ);
00126     deselect();
00127     return val;
00128     }
00129 
00130 void lps331::writeRegister(uint8_t address, uint8_t value){
00131      select();
00132     spi.write(WRITE | address);
00133     spi.write(value);
00134     deselect();
00135 }