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发表于 2014-9-24 23:41:15
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本帖最后由 topdog 于 2014-9-24 23:44 编辑
SFE_BMP180.cpp
#include <SFE_BMP180.h>
#include <Wire.h>
#include <stdio.h>
#include <math.h>
SFE_BMP180::SFE_BMP180()
// Base library type
{
}
char SFE_BMP180::begin()
// Initialize library for subsequent pressure measurements
{
double c3,c4,b1;
// Start up the Arduino's "wire" (I2C) library:
Wire.begin();
// The BMP180 includes factory calibration data stored on the device.
// Each device has different numbers, these must be retrieved and
// used in the calculations when taking pressure measurements.
// Retrieve calibration data from device:
if (readInt(0xAA,AC1) &&
readInt(0xAC,AC2) &&
readInt(0xAE,AC3) &&
readUInt(0xB0,AC4) &&
readUInt(0xB2,AC5) &&
readUInt(0xB4,AC6) &&
readInt(0xB6,VB1) &&
readInt(0xB8,VB2) &&
readInt(0xBA,MB) &&
readInt(0xBC,MC) &&
readInt(0xBE,MD))
{
// All reads completed successfully!
// If you need to check your math using known numbers,
// you can uncomment one of these examples.
// (The correct results are commented in the below functions.)
// Example from Bosch datasheet
// AC1 = 408; AC2 = -72; AC3 = -14383; AC4 = 32741; AC5 = 32757; AC6 = 23153;
// B1 = 6190; B2 = 4; MB = -32768; MC = -8711; MD = 2868;
// Example from http://wmrx00.sourceforge.net/Arduino/BMP180-Calcs.pdf
// AC1 = 7911; AC2 = -934; AC3 = -14306; AC4 = 31567; AC5 = 25671; AC6 = 18974;
// VB1 = 5498; VB2 = 46; MB = -32768; MC = -11075; MD = 2432;
/*
Serial.print("AC1: "); Serial.println(AC1);
Serial.print("AC2: "); Serial.println(AC2);
Serial.print("AC3: "); Serial.println(AC3);
Serial.print("AC4: "); Serial.println(AC4);
Serial.print("AC5: "); Serial.println(AC5);
Serial.print("AC6: "); Serial.println(AC6);
Serial.print("VB1: "); Serial.println(VB1);
Serial.print("VB2: "); Serial.println(VB2);
Serial.print("MB: "); Serial.println(MB);
Serial.print("MC: "); Serial.println(MC);
Serial.print("MD: "); Serial.println(MD);
*/
// Compute floating-point polynominals:
c3 = 160.0 * pow(2,-15) * AC3;
c4 = pow(10,-3) * pow(2,-15) * AC4;
b1 = pow(160,2) * pow(2,-30) * VB1;
c5 = (pow(2,-15) / 160) * AC5;
c6 = AC6;
mc = (pow(2,11) / pow(160,2)) * MC;
md = MD / 160.0;
x0 = AC1;
x1 = 160.0 * pow(2,-13) * AC2;
x2 = pow(160,2) * pow(2,-25) * VB2;
y0 = c4 * pow(2,15);
y1 = c4 * c3;
y2 = c4 * b1;
p0 = (3791.0 - 8.0) / 1600.0;
p1 = 1.0 - 7357.0 * pow(2,-20);
p2 = 3038.0 * 100.0 * pow(2,-36);
/*
Serial.println();
Serial.print("c3: "); Serial.println(c3);
Serial.print("c4: "); Serial.println(c4);
Serial.print("c5: "); Serial.println(c5);
Serial.print("c6: "); Serial.println(c6);
Serial.print("b1: "); Serial.println(b1);
Serial.print("mc: "); Serial.println(mc);
Serial.print("md: "); Serial.println(md);
Serial.print("x0: "); Serial.println(x0);
Serial.print("x1: "); Serial.println(x1);
Serial.print("x2: "); Serial.println(x2);
Serial.print("y0: "); Serial.println(y0);
Serial.print("y1: "); Serial.println(y1);
Serial.print("y2: "); Serial.println(y2);
Serial.print("p0: "); Serial.println(p0);
Serial.print("p1: "); Serial.println(p1);
Serial.print("p2: "); Serial.println(p2);
*/
// Success!
return(1);
}
else
{
// Error reading calibration data; bad component or connection?
return(0);
}
}
char SFE_BMP180::readInt(char address, int &value)
// Read a signed integer (two bytes) from device
// address: register to start reading (plus subsequent register)
// value: external variable to store data (function modifies value)
{
unsigned char data[2];
data[0] = address;
if (readBytes(data,2))
{
value = (((int)data[0]<<8)|(int)data[1]);
//if (*value & 0x8000) *value |= 0xFFFF0000; // sign extend if negative
return(1);
}
value = 0;
return(0);
}
char SFE_BMP180::readUInt(char address, unsigned int &value)
// Read an unsigned integer (two bytes) from device
// address: register to start reading (plus subsequent register)
// value: external variable to store data (function modifies value)
{
unsigned char data[2];
data[0] = address;
if (readBytes(data,2))
{
value = (((unsigned int)data[0]<<8)|(unsigned int)data[1]);
return(1);
}
value = 0;
return(0);
}
char SFE_BMP180::readBytes(unsigned char *values, char length)
// Read an array of bytes from device
// values: external array to hold data. Put starting register in values[0].
// length: number of bytes to read
{
char x;
Wire.beginTransmission(BMP180_ADDR);
Wire.write(values[0]);
_error = Wire.endTransmission();
if (_error == 0)
{
Wire.requestFrom(BMP180_ADDR,length);
while(Wire.available() != length) ; // wait until bytes are ready
for(x=0;x<length;x++)
{
values[x] = Wire.read();
}
return(1);
}
return(0);
}
char SFE_BMP180::writeBytes(unsigned char *values, char length)
// Write an array of bytes to device
// values: external array of data to write. Put starting register in values[0].
// length: number of bytes to write
{
char x;
Wire.beginTransmission(BMP180_ADDR);
Wire.write(values,length);
_error = Wire.endTransmission();
if (_error == 0)
return(1);
else
return(0);
}
char SFE_BMP180::startTemperature(void)
// Begin a temperature reading.
// Will return delay in ms to wait, or 0 if I2C error
{
unsigned char data[2], result;
data[0] = BMP180_REG_CONTROL;
data[1] = BMP180_COMMAND_TEMPERATURE;
result = writeBytes(data, 2);
if (result) // good write?
return(5); // return the delay in ms (rounded up) to wait before retrieving data
else
return(0); // or return 0 if there was a problem communicating with the BMP
}
char SFE_BMP180::getTemperature(double &T)
// Retrieve a previously-started temperature reading.
// Requires begin() to be called once prior to retrieve calibration parameters.
// Requires startTemperature() to have been called prior and sufficient time elapsed.
// T: external variable to hold result.
// Returns 1 if successful, 0 if I2C error.
{
unsigned char data[2];
char result;
double tu, a;
data[0] = BMP180_REG_RESULT;
result = readBytes(data, 2);
if (result) // good read, calculate temperature
{
tu = (data[0] * 256.0) + data[1];
//example from Bosch datasheet
//tu = 27898;
//example from http://wmrx00.sourceforge.net/Arduino/BMP085-Calcs.pdf
//tu = 0x69EC;
a = c5 * (tu - c6);
T = a + (mc / (a + md));
/*
Serial.println();
Serial.print("tu: "); Serial.println(tu);
Serial.print("a: "); Serial.println(a);
Serial.print("T: "); Serial.println(*T);
*/
}
return(result);
}
char SFE_BMP180::startPressure(char oversampling)
// Begin a pressure reading.
// Oversampling: 0 to 3, higher numbers are slower, higher-res outputs.
// Will return delay in ms to wait, or 0 if I2C error.
{
unsigned char data[2], result, delay;
data[0] = BMP180_REG_CONTROL;
switch (oversampling)
{
case 0:
data[1] = BMP180_COMMAND_PRESSURE0;
delay = 5;
break;
case 1:
data[1] = BMP180_COMMAND_PRESSURE1;
delay = 8;
break;
case 2:
data[1] = BMP180_COMMAND_PRESSURE2;
delay = 14;
break;
case 3:
data[1] = BMP180_COMMAND_PRESSURE3;
delay = 26;
break;
default:
data[1] = BMP180_COMMAND_PRESSURE0;
delay = 5;
break;
}
result = writeBytes(data, 2);
if (result) // good write?
return(delay); // return the delay in ms (rounded up) to wait before retrieving data
else
return(0); // or return 0 if there was a problem communicating with the BMP
}
char SFE_BMP180::getPressure(double &P, double &T)
// Retrieve a previously started pressure reading, calculate abolute pressure in mbars.
// Requires begin() to be called once prior to retrieve calibration parameters.
// Requires startPressure() to have been called prior and sufficient time elapsed.
// Requires recent temperature reading to accurately calculate pressure.
// P: external variable to hold pressure.
// T: previously-calculated temperature.
// Returns 1 for success, 0 for I2C error.
// Note that calculated pressure value is absolute mbars, to compensate for altitude call sealevel().
{
unsigned char data[3];
char result;
double pu,s,x,y,z;
data[0] = BMP180_REG_RESULT;
result = readBytes(data, 3);
if (result) // good read, calculate pressure
{
pu = (data[0] * 256.0) + data[1] + (data[2]/256.0);
//example from Bosch datasheet
//pu = 23843;
//example from http://wmrx00.sourceforge.net/Arduino/BMP085-Calcs.pdf, pu = 0x982FC0;
//pu = (0x98 * 256.0) + 0x2F + (0xC0/256.0);
s = T - 25.0;
x = (x2 * pow(s,2)) + (x1 * s) + x0;
y = (y2 * pow(s,2)) + (y1 * s) + y0;
z = (pu - x) / y;
P = (p2 * pow(z,2)) + (p1 * z) + p0;
/*
Serial.println();
Serial.print("pu: "); Serial.println(pu);
Serial.print("T: "); Serial.println(*T);
Serial.print("s: "); Serial.println(s);
Serial.print("x: "); Serial.println(x);
Serial.print("y: "); Serial.println(y);
Serial.print("z: "); Serial.println(z);
Serial.print("P: "); Serial.println(*P);
*/
}
return(result);
}
double SFE_BMP180::sealevel(double P, double A)
// Given a pressure P (mb) taken at a specific altitude (meters),
// return the equivalent pressure (mb) at sea level.
// This produces pressure readings that can be used for weather measurements.
{
return(P/pow(1-(A/44330.0),5.255));
}
double SFE_BMP180::altitude(double P, double P0)
// Given a pressure measurement P (mb) and the pressure at a baseline P0 (mb),
// return altitude (meters) above baseline.
{
return(44330.0*(1-pow(P/P0,1/5.255)));
}
char SFE_BMP180::getError(void)
// If any library command fails, you can retrieve an extended
// error code using this command. Errors are from the wire library:
// 0 = Success
// 1 = Data too long to fit in transmit buffer
// 2 = Received NACK on transmit of address
// 3 = Received NACK on transmit of data
// 4 = Other error
{
return(_error);
}
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