I think I found the problem...
The library tries to read two registers at once performing a "read16()", but the chip seems not to support that. The second register ist always return as 0xff.
I figured that out when I analyzed the data without oversampling, there the lsb was always 0xff. When using ultrahighres oversampling (default) then there is a shift with 3 bits that makes it difficult to see that directly...
The same applies to the reading for the temperature (which had in my case a resolution of approx. 1C).
I have replaced the read16() with two read8() commands and some additional shifting and will test it further. If anyone would like to test it also, the changed ZUNO_BMP180.cpp is below.
Regards,
Andreas.
Code: Select all
/***************************************************
This is a library for the Adafruit BMP085/BMP180 Barometric Pressure + Temp sensor
Designed specifically to work with the Adafruit BMP085 or BMP180 Breakout
----> http://www.adafruit.com/products/391
----> http://www.adafruit.com/products/1603
These displays use I2C to communicate, 2 pins are required to
interface
Adafruit invests time and resources providing this open source code,
please support Adafruit and open-source hardware by purchasing
products from Adafruit!
Written by Limor Fried/Ladyada for Adafruit Industries.
BSD license, all text above must be included in any redistribution
****************************************************/
#include "ZUNO_BMP180.h"
#include "Wire.h"
//#define BMP085_DEBUG 1
#define _delay_ms(d) delay(d)
ZUNO_BMP180::ZUNO_BMP180() {
}
boolean ZUNO_BMP180::begin(uint8_t mode) {
if (mode > BMP085_ULTRAHIGHRES)
mode = BMP085_ULTRAHIGHRES;
oversampling = mode;
Wire.begin();
if (read8(0xD0) != 0x55) return false;
/* read calibration data */
ac1 = read16(BMP085_CAL_AC1);
ac2 = read16(BMP085_CAL_AC2);
ac3 = read16(BMP085_CAL_AC3);
ac4 = read16(BMP085_CAL_AC4);
ac5 = read16(BMP085_CAL_AC5);
ac6 = read16(BMP085_CAL_AC6);
b1 = read16(BMP085_CAL_B1);
b2 = read16(BMP085_CAL_B2);
mb = read16(BMP085_CAL_MB);
mc = read16(BMP085_CAL_MC);
md = read16(BMP085_CAL_MD);
}
void ZUNO_BMP180::dumpInternal()
{
Serial.print("ac1 = "); Serial.println(ac1, DEC);
Serial.print("ac2 = "); Serial.println(ac2, DEC);
Serial.print("ac3 = "); Serial.println(ac3, DEC);
Serial.print("ac4 = "); Serial.println(ac4, DEC);
Serial.print("ac5 = "); Serial.println(ac5, DEC);
Serial.print("ac6 = "); Serial.println(ac6, DEC);
Serial.print("b1 = "); Serial.println(b1, DEC);
Serial.print("b2 = "); Serial.println(b2, DEC);
Serial.print("mb = "); Serial.println(mb, DEC);
Serial.print("mc = "); Serial.println(mc, DEC);
Serial.print("md = "); Serial.println(md, DEC);
}
uint16_t ZUNO_BMP180::readRawTemperature(void) {
uint16_t t;
write8(BMP085_CONTROL, BMP085_READTEMPCMD);
_delay_ms(5);
t = read8(BMP085_TEMPDATA);
t <<= 8;
t |= read8(BMP085_TEMPDATA+1);
return t;
}
uint32_t ZUNO_BMP180::readRawPressure(void) {
uint32_t raw;
write8(BMP085_CONTROL, BMP085_READPRESSURECMD + (oversampling << 6));
if (oversampling == BMP085_ULTRALOWPOWER)
_delay_ms(5);
else if (oversampling == BMP085_STANDARD)
_delay_ms(8);
else if (oversampling == BMP085_HIGHRES)
_delay_ms(14);
else
_delay_ms(26);
raw = read8(BMP085_PRESSUREDATA);
raw <<= 8;
raw |= read8(BMP085_PRESSUREDATA+1);
raw <<= 8;
raw |= read8(BMP085_PRESSUREDATA+2);
raw >>= (8 - oversampling);
return raw;
}
int32_t ZUNO_BMP180::readPressure(void) {
int16_t UT = readRawTemperature();
long UP = readRawPressure();
long X1 = UT - ac6;
long X2 = mc;
X1 *= ac5;
X1 >>= 15;
X2 <<= 11;
X2 /= (X1 + md);
//1) => B5 => B6
long B6 = (X1 + X2) - 4000;
//2) X1
// X1 = (B2*(B6*B6)/2^12)/2^11
X2 = X1 = B6;
X1 *= B6;
X1 >>= 12;
uint16_t koef1 = X1;
X1 *= b2;
X1 >>= 11;
//3)
// X2 = ac2*b6/2^11
X2 *= ac2;
X2 >>= 11;
// 4
// B3 = ((4*ac1 + X1 + X2)*2^(oversampling) + 2) / 4
long B3 = ac1;
B3 <<= 2;
B3 += X1 + X2;
B3 <<= oversampling;
B3 >>= 2;
B3 = UP-B3; // B7
B3 *= (50000 >> oversampling);
// 5)
// X1 = AC3*B6/2^13
X1 = ac3;
X1 *= B6;
X1 >>= 13;
// 6)
// X2 = (b1*b6*b6/2^12)/2^16
X2 = b1;
X2 *= koef1;
X2 >>= 16;
//
X1 += X2 + 2;
X1 >>= 2;
// B4....
unsigned long B4 = X1;
B4 += 32768;
B4 *= ac4;
B4 >>= 15;
long p = B3 < 0x80000000 ? (B3 << 1) / B4 : (B3/B4) << 1;
X1 = p >> 8;
X1 *= X1;
X1 *= 3038;
X1 >>= 16;
X2 = p;
X2 *= -7357;
X2 >>= 16;
X1 += X2 + 3791;
X1 >>= 4;
p += X1;
return p;
}
int16_t ZUNO_BMP180::readTemperatureC10(void) {
int16_t UT = readRawTemperature();
//Serial.print("UT=");
//Serial.println(UT);
long X1 = UT - ac6;
long X2 = mc;
X1 *= ac5;
X1 >>= 15;
X2 <<= 11;
X2 /= (X1 + md);
X1 += X2 + 8;
X1 >>= 4;
return (int16_t) X1;
}
float ZUNO_BMP180::readTemperature(void)
{
return readTemperatureC10() / 10.0;
}
float ZUNO_BMP180::readAltitude(float sealevelPressure) {
float altitude;
float pressure = readPressure();
altitude = 44330 * (1.0 - pow(pressure /sealevelPressure,0.1903));
return altitude;
}
/*********************************************************************/
uint8_t ZUNO_BMP180::read8(uint8_t a) {
uint8_t ret;
Wire.beginTransmission(BMP085_I2CADDR); // start transmission to device
Wire.write(a); // sends register address to read from
Wire.endTransmission(); // end transmission
//Wire.beginTransmission(BMP085_I2CADDR); // start transmission to device
Wire.requestFrom(BMP085_I2CADDR, 1);// send data n-bytes read
ret = Wire.read(); // receive DATA
//Wire.endTransmission(); // end transmission
return ret;
}
uint16_t ZUNO_BMP180::read16(uint8_t a) {
uint16_t ret;
Wire.beginTransmission(BMP085_I2CADDR); // start transmission to device
Wire.write(a); // sends register address to read from
Wire.endTransmission(); // end transmission
//Wire.beginTransmission(BMP085_I2CADDR); // start transmission to device
Wire.requestFrom(BMP085_I2CADDR, 2);// send data n-bytes read
ret = Wire.read(); // receive DATA
ret <<= 8;
ret |= Wire.read(); // receive DATA
//Wire.endTransmission(); // end transmission
return ret;
}
void ZUNO_BMP180::write8(uint8_t a, uint8_t d) {
Wire.beginTransmission(BMP085_I2CADDR); // start transmission to device
Wire.write(a); // sends register address to read from
Wire.write(d); // write data
Wire.endTransmission(); // end transmission
}
