Hola compañeros. Estoy tratando de crear un barometro mediante un sensor BMP180 y un arduino MEGA 2560. Se de la existencia de la libreria especifica para este modelo, pero tambien es posible realizarlo solo con la libreria "whire.h". He encontrado un codigo en internet, pero leyendo el datasheet del dispositivo hay cosas que no comprendo, y los resultados de presion on de una diferencia de 200mb aprox.
//Arduino 1.0+ Only
//Arduino 1.0+ Only
/*Based largely on code by Jim Lindblom
Get pressure, altitude, and temperature from the BMP085.
Serial.print it out at 9600 baud to serial monitor.
*/
#include <Wire.h>
#define BMP085_ADDRESS 0x77 // I2C address of BMP085
//#define BMP085_ADDRESS 0x55 // I2C address of BMP180
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;
void bmp085Calibration()
{
ac1 = bmp085ReadInt(0xAA);
ac2 = bmp085ReadInt(0xAB);
ac3 = bmp085ReadInt(0xAE);
ac4 = bmp085ReadInt(0xB0);
ac5 = bmp085ReadInt(0xB2);
ac6 = bmp085ReadInt(0xB4);
b1 = bmp085ReadInt(0xB6);
b2 = bmp085ReadInt(0xB8);
mb = bmp085ReadInt(0xBA);
mc = bmp085ReadInt(0xBB);
md = bmp085ReadInt(0xBE);
}
void setup(){
Serial.begin(9600);
Wire.begin();
Serial.println ("Practica 32: Barometro y Termometro");
Serial.print ("Inicio de Calibracion : ");
Serial.println (millis());
bmp085Calibration();
Serial.print ("Fin de Calibracion : ");
Serial.println (millis());
}
void loop()
{
float hpa;
float mmhg;
float pascal = bmp085GetPressure(bmp085ReadUP()); // devuelve pascales
float atm = pascal / 1013; // "standard atmosphere"
float altitude = calcAltitude(pascal); //Uncompensated caculation - in Meters
hpa=pascal/100;
mmhg=hpa*0.76;
Serial.print ("Presion: ");
Serial.print (hpa);
Serial.println ("Hpa");
Serial.print ("Presion: ");
Serial.print (mmhg);
Serial.println ("mmhg");
Serial.print ("Presion: ");
Serial.print (hpa);
Serial.println ("mb");
Serial.print ("Presion: ");
Serial.print (atm);
Serial.println ("atm");
/*
Serial.print("Pressure: ");
Serial.print(pressure, 0); //whole number only.
Serial.println(" Pa");
Serial.print("Standard Atmosphere: ");
Serial.println(atm, 4); //display 4 decimal places
Serial.print("Altitude: ");
Serial.print(altitude, 2); //display 2 decimal places
Serial.println(" M");
*/
Serial.println();//line break
delay(1000); //wait a second and get values again.
}
// 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
// Calculate temperature in deg C
float bmp085GetTemperature(unsigned int ut){
long x1, x2;
x1 = (((long)ut - (long)ac6)*(long)ac5) >> 15;
x2 = ((long)mc << 11)/(x1 + md);
b5 = x1 + x2;
float temp = ((b5 + 8)>>4);
temp = temp /10;
return temp;
}
// 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;
long temp = p;
return temp;
}
// 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)
msb = bmp085Read(0xF6);
lsb = bmp085Read(0xF7);
xlsb = bmp085Read(0xF8);
up = (((unsigned long) msb << 16) | ((unsigned long) lsb << 8) | (unsigned long) xlsb) >> (8-OSS);
return up;
}
void writeRegister(int deviceAddress, byte address, byte val) {
Wire.beginTransmission(deviceAddress); // start transmission to device
Wire.write(address); // send register address
Wire.write(val); // send value to write
Wire.endTransmission(); // end transmission
}
int readRegister(int deviceAddress, byte address){
int v;
Wire.beginTransmission(deviceAddress);
Wire.write(address); // register to read
Wire.endTransmission();
Wire.requestFrom(deviceAddress, 1); // read a byte
while(!Wire.available()) {
// waiting
}
v = Wire.read();
return v;
}
float calcAltitude(float pressure){
float A = pressure/101325;
float B = 1/5.25588;
float C = pow(A,B);
C = 1 - C;
C = C /0.0000225577;
return C;
}
Arriba hay 2 "#define" , supuestamente uno para el BMP085(0x77) y otro para el BMP180(0x55). En BMP180, en el datasheet aparece tambien que usa el 0x55, como bien indica el programa. Sin embargo, cambio esa parte del codigo y a la hora de ejecutarlo no hace absolutamente nada. Sin embargo si lo dejo con la supuesta configuracion del BMP085 si funciona, y como anteriormente he dicho, da valores con una diferencia de +200mb aproximandamente, algo mas. Las direcciones de memoria para la calibracion son correctas, tambien las he mirado en el pdf, no se que puede ser, o si es que solo funciona con 0x77. ¿Se supone que deberia usar el suyo y las medidas serian mas exactas no?
https://cdn-shop.adafruit.com/datasheets/BST-BMP180-DS000-09.pdf --> Datasheet del sensor
Haber si resuelvo esta duda, un saludo y gracias por vuestro tiempo
