MS5837.cpp

00001 #include <stdlib.h>
00002 #include "MS5837.h"
00003 
00004 
00005 /*
00006  * Sensor operating function according data sheet
00007  */
00008 
00009 void MS5837::MS5837Init(void)
00010 {
00011     MS5837Reset();
00012     MS5837ReadProm();
00013     return;
00014 }
00015 
00016 /* Send soft reset to the sensor */
00017 void MS5837::MS5837Reset(void)
00018 {
00019     /* transmit out 1 byte reset command */
00020     ms5837_tx_data[0] = ms5837_reset;
00021     if ( i2c.write( device_address,  ms5837_tx_data, 1 ) );
00022     //printf("send soft reset");
00023     wait_ms(20);
00024 }
00025 
00026 /* read the sensor calibration data from rom */
00027 void MS5837::MS5837ReadProm(void)
00028 {
00029     uint8_t i,j;
00030     for (i=0; i<8; i++) {
00031         j = i;
00032         ms5837_tx_data[0] = ms5837_PROMread + (j<<1);
00033         if ( i2c.write( device_address,  ms5837_tx_data, 1 ) );
00034         if ( i2c.read( device_address,  ms5837_rx_data, 2 ) );
00035         C[i]   = ms5837_rx_data[1] + (ms5837_rx_data[0]<<8);
00036     }
00037 }
00038 
00039 /* Start the sensor pressure conversion */
00040 void MS5837::MS5837ConvertD1(void)
00041 {
00042     ms5837_tx_data[0] = ms5837_convD1;
00043     if ( i2c.write( device_address,  ms5837_tx_data, 1 ) );
00044 }
00045 
00046 /* Start the sensor temperature conversion */
00047 void MS5837:: MS5837ConvertD2(void)
00048 {
00049     ms5837_tx_data[0] = ms5837_convD2;
00050     if ( i2c.write( device_address,  ms5837_tx_data, 1 ) );
00051 }
00052 
00053 /* Read the previous started conversion results */
00054 int32_t MS5837::MS5837ReadADC(void)
00055 {
00056     int32_t adc;
00057     wait_ms(150);
00058     ms5837_tx_data[0] = ms5837_ADCread;
00059     if ( i2c.write( device_address,  ms5837_tx_data, 1 ) );
00060     if ( i2c.read( device_address,  ms5837_rx_data, 3 ) );
00061     adc = ms5837_rx_data[2] + (ms5837_rx_data[1]<<8) + (ms5837_rx_data[0]<<16);
00062     return (adc);
00063 }
00064 
00065 /* return the results */
00066 float MS5837::MS5837_Pressure (void)
00067 {
00068     return P_MS5837;
00069 }
00070 float MS5837::MS5837_Temperature (void)
00071 {
00072     return T_MS5837;
00073 }
00074 
00075 /* Sensor reading and calculation procedure */
00076 void MS5837::Barometer_MS5837(void)
00077 {
00078     int32_t dT, temp;
00079     int64_t OFF, SENS, press;
00080 
00081     //no need to do this everytime!
00082     //MS5837Reset();                 // reset the sensor
00083     //MS5837ReadProm();             // read the calibration values
00084     
00085     
00086     MS5837ConvertD1();             // start pressure conversion
00087     D1 = MS5837ReadADC();        // read the pressure value
00088     MS5837ConvertD2();             // start temperature conversion
00089     D2 = MS5837ReadADC();         // read the temperature value
00090 
00091     /* calculation according MS5837-01BA data sheet DA5837-01BA_006 */
00092     dT       = D2 - (C[5]* 256);
00093     OFF      = (int64_t)C[2] * (1<<16) + ((int64_t)dT * (int64_t)C[4]) / (1<<7);
00094     SENS     = (int64_t)C[1] * (1<<15) + ((int64_t)dT * (int64_t)C[3]) / (1<<8);
00095 
00096     temp     = 2000 + (dT * C[6]) / (1<<23);
00097     T_MS5837 = (float) temp / 100.0f;                 // result of temperature in deg C in this var
00098     press    = (((int64_t)D1 * SENS) / (1<<21) - OFF) / (1<<13);
00099     P_MS5837 = (float) press / 10.0f;                 // result of pressure in mBar in this var
00100 }