Difference between revisions of "BMP085 Barometric Pressure Sensor Breakout"
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==Example code== | ==Example code== | ||
+ | For Arduino 1.0+ | ||
+ | |||
#include <Wire.h> | #include <Wire.h> | ||
− | #define BMP085_ADDRESS 0x77 // I2C address of BMP085 | + | #define BMP085_ADDRESS 0x77 // I2C address of BMP085 |
− | const unsigned char OSS = 0; // Oversampling Setting | + | const unsigned char OSS = 0; // Oversampling Setting |
− | // Calibration values | + | // Calibration values |
− | int ac1; | + | int ac1; |
− | int ac2; | + | int ac2; |
− | int ac3; | + | int ac3; |
− | unsigned int ac4; | + | unsigned int ac4; |
− | unsigned int ac5; | + | unsigned int ac5; |
− | unsigned int ac6; | + | unsigned int ac6; |
− | int b1; | + | int b1; |
− | int b2; | + | int b2; |
− | int mb; | + | int mb; |
− | int mc; | + | int mc; |
− | int md; | + | int md; |
− | // b5 is calculated in bmp085GetTemperature(...), this variable is also used in bmp085GetPressure(...) | + | // b5 is calculated in bmp085GetTemperature(...), this variable is also used in bmp085GetPressure(...) |
− | // so ...Temperature(...) must be called before ...Pressure(...). | + | // so ...Temperature(...) must be called before ...Pressure(...). |
− | long b5; | + | long b5; |
− | short temperature; | + | short temperature; |
− | long pressure; | + | long pressure; |
− | void setup() | + | void setup() |
− | { | + | { |
Serial.begin(9600); | Serial.begin(9600); | ||
Wire.begin(); | Wire.begin(); | ||
bmp085Calibration(); | bmp085Calibration(); | ||
− | } | + | } |
− | void loop() | + | void loop() |
− | { | + | { |
temperature = bmp085GetTemperature(bmp085ReadUT()); | temperature = bmp085GetTemperature(bmp085ReadUT()); | ||
pressure = bmp085GetPressure(bmp085ReadUP()); | pressure = bmp085GetPressure(bmp085ReadUP()); | ||
Line 64: | Line 66: | ||
Serial.println(); | Serial.println(); | ||
delay(1000); | delay(1000); | ||
− | } | + | } |
− | // Stores all of the bmp085's calibration values into global variables | + | // Stores all of the bmp085's calibration values into global variables |
− | // Calibration values are required to calculate temp and pressure | + | // Calibration values are required to calculate temp and pressure |
− | // This function should be called at the beginning of the program | + | // This function should be called at the beginning of the program |
− | void bmp085Calibration() | + | void bmp085Calibration() |
− | { | + | { |
ac1 = bmp085ReadInt(0xAA); | ac1 = bmp085ReadInt(0xAA); | ||
ac2 = bmp085ReadInt(0xAC); | ac2 = bmp085ReadInt(0xAC); | ||
Line 81: | Line 83: | ||
mc = bmp085ReadInt(0xBC); | mc = bmp085ReadInt(0xBC); | ||
md = bmp085ReadInt(0xBE); | md = bmp085ReadInt(0xBE); | ||
− | } | + | } |
− | // Calculate temperature given ut. | + | // Calculate temperature given ut. |
− | // Value returned will be in units of 0.1 deg C | + | // Value returned will be in units of 0.1 deg C |
− | short bmp085GetTemperature(unsigned int ut) | + | short bmp085GetTemperature(unsigned int ut) |
− | { | + | { |
long x1, x2; | long x1, x2; | ||
x1 = (((long)ut - (long)ac6)*(long)ac5) >> 15; | x1 = (((long)ut - (long)ac6)*(long)ac5) >> 15; | ||
Line 91: | Line 93: | ||
b5 = x1 + x2; | b5 = x1 + x2; | ||
return ((b5 + 8)>>4); | return ((b5 + 8)>>4); | ||
− | } | + | } |
− | // Calculate pressure given up | + | // Calculate pressure given up |
− | // calibration values must be known | + | // calibration values must be known |
− | // b5 is also required so bmp085GetTemperature(...) must be called first. | + | // b5 is also required so bmp085GetTemperature(...) must be called first. |
− | // Value returned will be pressure in units of Pa. | + | // Value returned will be pressure in units of Pa. |
− | long bmp085GetPressure(unsigned long up) | + | long bmp085GetPressure(unsigned long up) |
− | { | + | { |
long x1, x2, x3, b3, b6, p; | long x1, x2, x3, b3, b6, p; | ||
unsigned long b4, b7; | unsigned long b4, b7; | ||
Line 121: | Line 123: | ||
p += (x1 + x2 + 3791)>>4; | p += (x1 + x2 + 3791)>>4; | ||
return p; | return p; | ||
− | } | + | } |
− | // Read 1 byte from the BMP085 at 'address' | + | // Read 1 byte from the BMP085 at 'address' |
− | char bmp085Read(unsigned char address) | + | char bmp085Read(unsigned char address) |
− | { | + | { |
unsigned char data; | unsigned char data; | ||
Wire.beginTransmission(BMP085_ADDRESS); | Wire.beginTransmission(BMP085_ADDRESS); | ||
Line 132: | Line 134: | ||
while(!Wire.available()); | while(!Wire.available()); | ||
return Wire.read(); | return Wire.read(); | ||
− | } | + | } |
− | // Read 2 bytes from the BMP085 | + | // Read 2 bytes from the BMP085 |
− | // First byte will be from 'address' | + | // First byte will be from 'address' |
− | // Second byte will be from 'address'+1 | + | // Second byte will be from 'address'+1 |
− | int bmp085ReadInt(unsigned char address) | + | int bmp085ReadInt(unsigned char address) |
− | { | + | { |
unsigned char msb, lsb; | unsigned char msb, lsb; | ||
Wire.beginTransmission(BMP085_ADDRESS); | Wire.beginTransmission(BMP085_ADDRESS); | ||
Line 147: | Line 149: | ||
lsb = Wire.read(); | lsb = Wire.read(); | ||
return (int) msb<<8 | lsb; | return (int) msb<<8 | lsb; | ||
− | } | + | } |
− | // Read the uncompensated temperature value | + | // Read the uncompensated temperature value |
− | unsigned int bmp085ReadUT() | + | unsigned int bmp085ReadUT() |
− | { | + | { |
unsigned int ut; | unsigned int ut; | ||
// Write 0x2E into Register 0xF4 | // Write 0x2E into Register 0xF4 | ||
Line 163: | Line 165: | ||
ut = bmp085ReadInt(0xF6); | ut = bmp085ReadInt(0xF6); | ||
return ut; | return ut; | ||
− | } | + | } |
− | // Read the uncompensated pressure value | + | // Read the uncompensated pressure value |
− | unsigned long bmp085ReadUP() | + | unsigned long bmp085ReadUP() |
− | { | + | { |
unsigned char msb, lsb, xlsb; | unsigned char msb, lsb, xlsb; | ||
unsigned long up = 0; | unsigned long up = 0; | ||
Line 189: | Line 191: | ||
up = (((unsigned long) msb << 16) | ((unsigned long) lsb << 8) | (unsigned long) xlsb) >> (8-OSS); | up = (((unsigned long) msb << 16) | ((unsigned long) lsb << 8) | (unsigned long) xlsb) >> (8-OSS); | ||
return up; | return up; | ||
− | } | + | } |
==How to buy== | ==How to buy== | ||
Click here to buy [http://www.geeetech.com/bmp085-breakoutbarometric-pressure-sensor-p-530.html BMP085 Barometric Pressure Sensor Breakout] | Click here to buy [http://www.geeetech.com/bmp085-breakoutbarometric-pressure-sensor-p-530.html BMP085 Barometric Pressure Sensor Breakout] |
Latest revision as of 01:51, 10 December 2012
Introduction
This is a breakout board for BOSCH BMP085 digital barometric pressure sensor.This breadboard-friendly board break out all pins of BMP085 to 6-pin pitch header.BMP085 offers a meauring range of 300 - 1100hPa with an absolute accuracy of 2.5hPa and a noise of down to 0.03hPa.At the same time,the BMP085 features low power consumption of down to 3uA.The sensors supports a voltage between 1.8 and 3.6V. It's designed to be connected directly to microcontroller via I2C bus. The very small and ultra-thin package make the BMP085 the sensor of choice for any mobile application requiring precise barametric pressure meaurement.
Features
- Digital two wire (I2C) interface
- Wide barometric pressure range
- Flexible supply voltage range
- Ultra-low power consumption
- Low noise measurement
- Fully calibrated
- Temperature measurement included
- Ultra-flat, small footprint
Document
Usage
Here is the guide illustrates how to connect an Arduino to the BMP085 breakout board.
Example code
For Arduino 1.0+
#include <Wire.h> #define BMP085_ADDRESS 0x77 // I2C address of BMP085 const unsigned char OSS = 0; // Oversampling Setting // Calibration values int ac1; int ac2; int ac3; unsigned int ac4; unsigned int ac5; unsigned int ac6; int b1; int b2; int mb; int mc; int md; // b5 is calculated in bmp085GetTemperature(...), this variable is also used in bmp085GetPressure(...) // so ...Temperature(...) must be called before ...Pressure(...). long b5; short temperature; long pressure; void setup() { Serial.begin(9600); Wire.begin(); bmp085Calibration(); } void loop() { temperature = bmp085GetTemperature(bmp085ReadUT()); pressure = bmp085GetPressure(bmp085ReadUP()); Serial.print("Temperature: "); Serial.print(temperature, DEC); Serial.println(" *0.1 deg C"); Serial.print("Pressure: "); Serial.print(pressure, DEC); Serial.println(" Pa"); Serial.println(); delay(1000); } // Stores all of the bmp085's calibration values into global variables // Calibration values are required to calculate temp and pressure // This function should be called at the beginning of the program void bmp085Calibration() { ac1 = bmp085ReadInt(0xAA); ac2 = bmp085ReadInt(0xAC); ac3 = bmp085ReadInt(0xAE); ac4 = bmp085ReadInt(0xB0); ac5 = bmp085ReadInt(0xB2); ac6 = bmp085ReadInt(0xB4); b1 = bmp085ReadInt(0xB6); b2 = bmp085ReadInt(0xB8); mb = bmp085ReadInt(0xBA); mc = bmp085ReadInt(0xBC); md = bmp085ReadInt(0xBE); } // Calculate temperature given ut. // Value returned will be in units of 0.1 deg C short bmp085GetTemperature(unsigned int ut) { long x1, x2; x1 = (((long)ut - (long)ac6)*(long)ac5) >> 15; x2 = ((long)mc << 11)/(x1 + md); b5 = x1 + x2; return ((b5 + 8)>>4); } // Calculate pressure given up // calibration values must be known // b5 is also required so bmp085GetTemperature(...) must be called first. // Value returned will be pressure in units of Pa. long bmp085GetPressure(unsigned long up) { long x1, x2, x3, b3, b6, p; unsigned long b4, b7; b6 = b5 - 4000; // Calculate B3 x1 = (b2 * (b6 * b6)>>12)>>11; x2 = (ac2 * b6)>>11; x3 = x1 + x2; b3 = (((((long)ac1)*4 + x3)<<OSS) + 2)>>2; // Calculate B4 x1 = (ac3 * b6)>>13; x2 = (b1 * ((b6 * b6)>>12))>>16; x3 = ((x1 + x2) + 2)>>2; b4 = (ac4 * (unsigned long)(x3 + 32768))>>15; b7 = ((unsigned long)(up - b3) * (50000>>OSS)); if (b7 < 0x80000000) p = (b7<<1)/b4; else p = (b7/b4)<<1; x1 = (p>>8) * (p>>8); x1 = (x1 * 3038)>>16; x2 = (-7357 * p)>>16; p += (x1 + x2 + 3791)>>4; return p; } // Read 1 byte from the BMP085 at 'address' char bmp085Read(unsigned char address) { unsigned char data; Wire.beginTransmission(BMP085_ADDRESS); Wire.write(address); Wire.endTransmission(); Wire.requestFrom(BMP085_ADDRESS, 1); while(!Wire.available()); return Wire.read(); } // Read 2 bytes from the BMP085 // First byte will be from 'address' // Second byte will be from 'address'+1 int bmp085ReadInt(unsigned char address) { unsigned char msb, lsb; Wire.beginTransmission(BMP085_ADDRESS); Wire.write(address); Wire.endTransmission(); Wire.requestFrom(BMP085_ADDRESS, 2); while(Wire.available()<2); msb = Wire.read(); lsb = Wire.read(); return (int) msb<<8 | lsb; } // Read the uncompensated temperature value unsigned int bmp085ReadUT() { unsigned int ut; // Write 0x2E into Register 0xF4 // This requests a temperature reading Wire.beginTransmission(BMP085_ADDRESS); Wire.write(0xF4); Wire.write(0x2E); Wire.endTransmission(); // Wait at least 4.5ms delay(5); // Read two bytes from registers 0xF6 and 0xF7 ut = bmp085ReadInt(0xF6); return ut; } // Read the uncompensated pressure value unsigned long bmp085ReadUP() { unsigned char msb, lsb, xlsb; unsigned long up = 0; // Write 0x34+(OSS<<6) into register 0xF4 // Request a pressure reading w/ oversampling setting Wire.beginTransmission(BMP085_ADDRESS); Wire.write(0xF4); Wire.write(0x34 + (OSS<<6)); Wire.endTransmission(); // Wait for conversion, delay time dependent on OSS delay(2 + (3<<OSS)); // Read register 0xF6 (MSB), 0xF7 (LSB), and 0xF8 (XLSB) Wire.beginTransmission(BMP085_ADDRESS); Wire.write(0xF6); Wire.endTransmission(); Wire.requestFrom(BMP085_ADDRESS, 3); // Wait for data to become available while(Wire.available() < 3); msb = Wire.read(); lsb = Wire.read(); xlsb = Wire.read(); up = (((unsigned long) msb << 16) | ((unsigned long) lsb << 8) | (unsigned long) xlsb) >> (8-OSS); return up; }
How to buy
Click here to buy BMP085 Barometric Pressure Sensor Breakout