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\n");
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     //printf("ADC value: %x\n", adc);
00063     return (adc);
00064 }
00065 
00066 /* return the results */
00067 float MS5837::MS5837_Pressure (void)
00068 {
00069     return P_MS5837;
00070 }
00071 float MS5837::MS5837_Temperature (void)
00072 {
00073     return T_MS5837;
00074 }
00075 
00076 /* Sensor reading and calculation procedure */
00077 void MS5837::Barometer_MS5837(void)
00078 {
00079     int32_t dT, temp;
00080     int64_t OFF, SENS, press;
00081     
00082     //int32_t dT = 0;
00083     //int64_t SENS = 0;
00084     //int64_t OFF = 0;
00085     int32_t SENSi = 0;
00086     int32_t OFFi = 0;  
00087     int32_t Ti = 0;    
00088     int64_t OFF2 = 0;
00089     int64_t SENS2 = 0;
00090 
00091     //no need to do this everytime!
00092     
00093     
00094     MS5837ConvertD1();             // start pressure conversion
00095     D1 = MS5837ReadADC();        // read the pressure value
00096     MS5837ConvertD2();             // start temperature conversion
00097     D2 = MS5837ReadADC();         // read the temperature value
00098     //printf("D1 = %d\n", D1);
00099     /* calculation according MS5837-01BA data sheet DA5837-01BA_006 */
00100     dT       = D2 - ((uint32_t)C[5]* 256);
00101     OFF      = (int64_t)C[2] * (1<<17) + ((int64_t)dT * (int64_t)C[4]) / (1<<6);
00102     SENS     = (int64_t)C[1] * (1<<16) + ((int64_t)dT * (int64_t)C[3]) / (1<<7);
00103 
00104     temp     = 2000 + ((int64_t)dT * C[6]) / (1<<23);
00105     press    = (((int64_t)D1 * SENS) / (1<<21) - OFF) / (1<<15);
00106     if((temp/100)<20){         //Low temp
00107             //Serial.println("here");
00108             Ti = (11*int64_t(dT)*int64_t(dT))/(34359738368LL);
00109             OFFi = (31*(temp-2000)*(temp-2000))/8;
00110             SENSi = (63*(temp-2000)*(temp-2000))/32;
00111     }
00112     
00113     OFF2 = OFF-OFFi;           //Calculate pressure and temp second order
00114     SENS2 = SENS-SENSi;
00115     
00116     temp = (temp-Ti);
00117     press = (((D1*SENS2)/2097152l-OFF2)/32768l)/100;
00118     
00119     T_MS5837 = (float) temp / 100.0f;                 // result of temperature in deg C in this var
00120     P_MS5837 = (float) press / 1.00f;                 // result of pressure in mBar in this var
00121     
00122 }
00123 
00124 float MS5837::depth(void) {
00125     //return (P_MS5837/100)*1.019716;
00126     return ((P_MS5837*100)-101300)/(fluidDensity*9.80665);
00127     
00128 }
00129 
00130 float MS5837::altitude(void) {
00131     //return (P_MS5837/100)*1.019716;
00132     return (1-pow((P_MS5837/1013.25),0.190284))*145366.45*0.3048;
00133     
00134 }