Lab 21/ HW 21

Lab 21 (BPM180):

// This is the top of the program
#include <Wire.h>
#include "BMP180Lib.c"
#include <SD.h>
#define BMP180_ADDRESS 0x77 // I2C address of BMP180

// 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;
}

short temperature;
long pressure;
// Use these for altitude conversions
const float p0 = 101325; // Pressure at sea level (Pa)
float altitude;
const int CS_PIN = 10;
void setup()
{
 Serial.begin(9600);
 Wire.begin();
 bmp180Calibration();
 Serial.println("Initializing Card");
 //CS pin is an output
 pinMode(CS_PIN, OUTPUT);
 if (!SD.begin(CS_PIN))
 {
  Serial.println("Card Failure");
  return;
 }
 Serial.println("Card Ready");
}
// Stores all of the bmp180'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);
}
// 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)
 Wire.beginTransmission(BMP180_ADDRESS);
 Wire.write(0xF6);
 Wire.endTransmission();
 Wire.requestFrom(BMP180_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;
}
unsigned long previousmillis = 0;
void loop()
{
 temperature = bmp180GetTemperature(bmp180ReadUT());
 pressure = bmp180GetPressure(bmp180ReadUP());
 altitude = (float)44330 * (1 - pow(((float) pressure/p0), 0.190295));
 unsigned long timestamp = millis();
 if(timestamp - previousmillis >= 2)
 {
 previousmillis = timestamp;
 File dataFile = SD.open("PTA.csv", FILE_WRITE);
 if (dataFile)
 {
  dataFile.print(timestamp);
  dataFile.print(",");
  dataFile.print(temperature*0.1);
  dataFile.print(",");
  dataFile.print(pressure);
  dataFile.print(",");
  dataFile.println(altitude, 2);
  dataFile.close();
 Serial.print(timestamp);
 Serial.print(",");
 Serial.print(temperature*0.1);
 Serial.print(",");
 Serial.print(pressure);
 Serial.print(",");
 Serial.println(altitude, 2);
 }
 else
 {
  Serial.println("Couldn't open log file");
 }
 }
}