Mein Code um den MS5611 auszulesen:
Code:
#include <Wire.h>
byte MS5611Address = false;
int64_t MS5611C[7];
unsigned long MS5611TimeConversion; // us
void MS5611Transmit(int command) {
if (!MS5611Address) return;
Wire.beginTransmission(MS5611Address);
Wire.write(command);
Wire.endTransmission();
}
int64_t MS5611Receive(int command, int bytes) {
if (!MS5611Address) return;
MS5611Transmit(command);
Wire.requestFrom(MS5611Address, bytes);
int64_t response = 0;
for (int i = 0; i < bytes; i++) response = (response << 8) | Wire.read();
return response;
}
void MS5611Reset() {
MS5611Transmit(0x1e);
delayMicroseconds(3000);
}
void MS5611ConvertD1() { // pressure conversion
MS5611Transmit(0x48); // OSR=4096
MS5611TimeConversion = micros() + 9040L;
}
void MS5611ConvertD2() { // temperature conversion
MS5611Transmit(0x50); // OSR=256
MS5611TimeConversion = micros() + 600L;
}
int64_t MS5611ReadADC() {
while (long(MS5611TimeConversion - micros()) > 0); // wait for conversion to be done
return MS5611Receive(0x00, 3);
}
int64_t MS5611ReadCalibration(int index) {
return MS5611Receive(0xa0 + index * 2, 2);
}
void MS5611Init() {
Wire.begin(); // start communication with MS5611 as master
MS5611Address = 0x76;
Wire.beginTransmission(MS5611Address);
if (Wire.endTransmission() != 0) {
MS5611Address = 0x77;
Wire.beginTransmission(MS5611Address);
if (Wire.endTransmission() != 0) {
MS5611Address = false;
return;
}
}
MS5611Reset(); // reset MS5611
for (int i = 1; i <= 6; i++) MS5611C[i] = MS5611ReadCalibration(i); // read calibration coefficients
MS5611ConvertD1(); // start the pressure conversion
}
void MS5611GetD1() {
MS5611C[0] = MS5611ReadADC(); // read the converted pressure started last time
MS5611ConvertD2(); // start the temperature conversion to be ready to read next time
}
float MS5611GetD2() {
int64_t D2 = MS5611ReadADC(); // read the converted temperature started last time
MS5611ConvertD1(); // start the pressure conversion to be ready to read next time
int64_t dT = D2 - (MS5611C[5] << 8);
int64_t TEMP = ((dT * MS5611C[6]) >> 23);
int64_t OFF = (MS5611C[2] << 16) + ((MS5611C[4] * dT) >> 7);
int64_t SENS = (MS5611C[1] << 15) + ((MS5611C[3] * dT) >> 8);
if (TEMP < 0) {
OFF -= (5 * TEMP * TEMP) >> 1;
SENS -= (5 * TEMP * TEMP) >> 2;
//TEMP -= (dT * dT) >> 31;
}
//temperature = 0.01 * (TEMP + 29315); // Kelvin
return (((MS5611C[0] * SENS) >> 21) - OFF) >> 15; // Pa
}
Damit passt die Temperaturmessung. Jedoch habe ich festgestellt, dass der MS5611 sich deutlich über die Umgebungstemperatur aufwärmt wenn er nahe an einem Abwärme erzeugenden Bauteil platziert ist (Spannungsregler, Microprozessor usw.)
Gruss Lukas
