Due with BMP180

Hello,

I have a small problem here. I'm using the Arduino Due to BMP180[http://www.exp-tech.de/adafruit-bmp180-barometric-pressure-temperature-altitude-sensor-5v-ready?___SID=U] as follows:

SCL = 21
SDA = 20
GND GND =
3V = 3,3v
Vin = open

Unfortunately, I get strange values:
Temp = 115 degrees, etc.

Can someone give me a hint?

Thank You

My code: (in the next Topic..)

Quite sure Vin shouldn't be open. Shouldn't it also be 3.3V? Do you have a schematic for the sensor?
Note: If you highlight your code, then click on this button on the menu bar, your code will be posted properly.

@dlloyd

Thanks, i have a schematic. I think thats ist free, but I look again after.
Thank You

#include <Wire.h>

#define BMP180_ADDRESS 0x77  // 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 bmp180GetTemperature(...), this variable is also used in bmp180GetPressure(...)
// so ...Temperature(...) must be called before ...Pressure(...).
long b5; 

void setup(){
  Serial.begin(9600);
  Wire.begin();
  Serial.println("Startup...");

  bmp180Calibration();
}

void loop()
{
  float temperature = bmp180GetTemperature(bmp180ReadUT()); //MUST be called first
  float pressure = bmp180GetPressure(bmp180ReadUP());
  float atm = pressure / 101325; // "standard atmosphere"
  float altitude = calcAltitude(pressure); //Uncompensated caculation - in Meters 

  Serial.print("Temperature: ");
  Serial.print(temperature, 2); //display 2 decimal places
  Serial.println("deg C");

  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(10000); //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
void bmp180Calibration()
{
  ac1 = bmp180ReadInt(0xAA);
  ac2 = bmp180ReadInt(0xAC);
  ac3 = bmp180ReadInt(0xAE);
  ac4 = bmp180ReadInt(0xB0);
  ac5 = bmp180ReadInt(0xB2);
  ac6 = bmp180ReadInt(0xB4);
  b1 = bmp180ReadInt(0xB6);
  b2 = bmp180ReadInt(0xB8);
  mb = bmp180ReadInt(0xBA);
  mc = bmp180ReadInt(0xBC);
  md = bmp180ReadInt(0xBE);
}

// Calculate temperature in deg C
float bmp180GetTemperature(unsigned int ut){
  long x1, x2;
  Serial.print(ut);
  Serial.print(" AC6: ");
  Serial.print(ac6);
  Serial.print(" AC5: ");
  Serial.println(ac5);

  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 bmp180GetTemperature(...) must be called first.
// Value returned will be pressure in units of Pa.
long bmp180GetPressure(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 BMP180 at 'address'
char bmp180Read(unsigned char address)
{
  unsigned char data;

  Wire.beginTransmission(BMP180_ADDRESS);
  Wire.write(address);
  Wire.endTransmission();

  Wire.requestFrom(BMP180_ADDRESS, 1);
  while(!Wire.available())
    ;

  return Wire.read();
}

// Read 2 bytes from the BMP180
// First byte will be from 'address'
// Second byte will be from 'address'+1
int bmp180ReadInt(unsigned char address)
{
  unsigned char msb, lsb;

  Wire.beginTransmission(BMP180_ADDRESS);
  Wire.write(address);
  Wire.endTransmission();

  Wire.requestFrom(BMP180_ADDRESS, 2);
  while(Wire.available()<2)
    ;
  msb = Wire.read();
  lsb = Wire.read();

  return (int) msb<<8 | lsb;
}

// Read the uncompensated temperature value
unsigned int bmp180ReadUT(){
  unsigned int ut;

  // Write 0x2E into Register 0xF4
  // This requests a temperature reading
  Wire.beginTransmission(BMP180_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 = bmp180ReadInt(0xF6);
  return ut;
}

// Read the uncompensated pressure value
unsigned long bmp180ReadUP(){

  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(BMP180_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 = bmp180Read(0xF6);
  lsb = bmp180Read(0xF7);
  xlsb = bmp180Read(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;
}

Hi,

i have Vin with 3.3V

23758 AC6: 15640 AC5: 25032
Temperature: 115.20deg C
Pressure: 12321 Pa
Standard Atmosphere: 0.1216
Altitude: 14641.39 M

without a change

Docu:
http://www.vssec.vic.edu.au/media/41229/BMP180-datasheet.pdf

hi,
These are the data from the Controller:

a1 7583
a2 64466
a3 50813
a4 33492
a5 25032
a6 15640
b1 6515
b2 38
mb 32768
mc 53750
md 2800

Temperature: 115.10deg C
Pressure: 12540 Pa
Standard Atmosphere: 0.1238
Altitude: 14541.70 M