Tyler Weaver
Pressure, Temperature, Altitude Sensor on breakout from sparkfun (I2C)
Diff: BMP085.cpp
- Revision:
- 0:0b4c4632aeb0
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/BMP085.cpp Wed Dec 12 16:30:14 2012 +0000
@@ -0,0 +1,234 @@
+/*
+ * @file BMP085.cpp
+ * @author Tyler Weaver
+ * @author Kory Hill
+ *
+ * @section LICENSE
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
+ * and associated documentation files (the "Software"), to deal in the Software without restriction,
+ * including without limitation the rights to use, copy, modify, merge, publish, distribute,
+ * sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all copies or
+ * substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
+ * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * @section DESCRIPTION
+ *
+ * BMP085 I2C Temperature/Pressure/Altitude Sensor
+ *
+ * Datasheet:
+ *
+ * http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Sensors/Pressure/BST-BMP085-DS000-06.pdf
+ */
+
+#include "BMP085.h"
+#include <new>
+
+BMP085::BMP085(PinName sda, PinName scl) : i2c_(*reinterpret_cast<I2C*>(i2cRaw))
+{
+ // Placement new to avoid additional heap memory allocation.
+ new(i2cRaw) I2C(sda, scl);
+
+ init();
+}
+
+BMP085::~BMP085()
+{
+ // If the I2C object is initialized in the buffer in this object, call destructor of it.
+ if(&i2c_ == reinterpret_cast<I2C*>(&i2cRaw))
+ reinterpret_cast<I2C*>(&i2cRaw)->~I2C();
+}
+
+void BMP085::init()
+{
+ get_cal_param();
+ set_oss(8); // standard over sampling (2 samples)
+ get_ut(); // initalize values
+ get_up();
+}
+
+void BMP085::get_cal_param()
+{
+ // get calibration values
+ AC1 = read_int16(0xAA);
+ AC2 = read_int16(0xAC);
+ AC3 = read_int16(0xAE);
+ AC4 = read_uint16(0xB0);
+ AC5 = read_uint16(0xB2);
+ AC6 = read_uint16(0xB4);
+ B1 = read_int16(0xB6);
+ B2 = read_int16(0xB8);
+ MB = read_int16(0xBA);
+ MC = read_int16(0xBC);
+ MD = read_int16(0xBE);
+}
+
+void BMP085::display_cal_param(Serial *pc)
+{
+ pc->printf("AC1 %x\r\n", AC1);
+ pc->printf("AC2 %x\r\n", AC2);
+ pc->printf("AC3 %x\r\n", AC3);
+ pc->printf("AC4 %x\r\n", AC4);
+ pc->printf("AC5 %x\r\n", AC5);
+ pc->printf("AC6 %x\r\n", AC6);
+ pc->printf("B1 %x\r\n", B1);
+ pc->printf("B2 %x\r\n", B2);
+ pc->printf("MB %x\r\n", MB);
+ pc->printf("MC %x\r\n", MC);
+ pc->printf("MD %x\r\n", MD);
+}
+
+void BMP085::get_ut()
+{
+ write_char(0xF4,0x2E);
+ wait(0.045);
+ char buffer[3];
+ read_multiple(0xF6, buffer, 2);
+
+ UT = (buffer[0]<<8) | buffer[1];
+}
+
+void BMP085::get_up()
+{
+ // set sample setting
+ write_char(0xF4, oversampling_setting_);
+
+ // wait
+ wait(conversion_time_);
+
+ // read the three bits
+ char buffer[3];
+ read_multiple(0xF6, buffer, 3);
+
+ UP = ((buffer[0]<<16) | (buffer[1]<<8) | (buffer[2])) >> (8 - oss_bit_);
+}
+
+void BMP085::set_oss(int oss)
+{
+ switch(oss) {
+ case 1: // low power
+ oss_bit_ = 0;
+ oversampling_setting_ = 0x34;
+ conversion_time_ = 0.045;
+ break;
+ case 2: // standard
+ oss_bit_ = 1;
+ oversampling_setting_ = 0x74;
+ conversion_time_ = 0.075;
+ break;
+ case 4: // high resolution
+ oss_bit_ = 2;
+ oversampling_setting_ = 0xB4;
+ conversion_time_ = 0.135;
+ break;
+ case 8: // ultra high resolution
+ oss_bit_ = 3;
+ oversampling_setting_ = 0xF4;
+ conversion_time_ = 0.255;
+ break;
+ default: // standard
+ oss_bit_ = 1;
+ oversampling_setting_ = 0x74;
+ conversion_time_ = 0.075;
+ }
+}
+
+void BMP085::write_char(char address, char data)
+{
+ char cmd[2];
+ cmd[0] = address;
+ cmd[1] = data;
+ i2c_.write( I2C_ADDRESS , cmd, 2);
+}
+
+int16_t BMP085::read_int16(char address)
+{
+ char tx[2];
+ tx[0] = address;
+ i2c_.write(I2C_ADDRESS, tx, 1);
+ i2c_.read(I2C_ADDRESS, tx, 2);
+ int16_t value = ((tx[0] << 8) | tx[1]);
+ return value;
+}
+
+void BMP085::read_multiple(char address, char* buffer, int bits)
+{
+ char cmd[2];
+ cmd[0] = address;
+ i2c_.write(I2C_ADDRESS, cmd, 1);
+ i2c_.read(I2C_ADDRESS, buffer, bits);
+}
+
+uint16_t BMP085::read_uint16(char address)
+{
+ char tx[2];
+ tx[0] = address;
+ i2c_.write(I2C_ADDRESS, tx, 1);
+ i2c_.read(I2C_ADDRESS, tx, 2);
+ uint16_t value = ((tx[0] << 8) | tx[1]);
+ return value;
+}
+
+int32_t BMP085::get_temperature()
+{
+ get_ut(); // uncompressed temperature
+ get_up(); // uncompressed pressure
+
+ long x1,x2;
+
+ //Start temperature calculation
+ x1 = ((UT - AC6) * AC5) >> 15;
+ x2 = (MC << 11) / (x1 + MD);
+ B5 = x1 + x2;
+ temperature = ((B5 + 8) >> 4);
+ return temperature;
+}
+
+int32_t BMP085::get_pressure()
+{
+ get_up(); // get uncompressed pressure (uncompressed temperature must be called recently)
+
+ B6 = B5 - 4000;
+ X1 = (B2 * ((B6 * B6) >> 12)) >> 11;
+ X2 = (AC2 * B6) >> 11;
+ X3 = X1 + X2;
+ B3 = ((((((long)(AC1) * 4) + X3) << oss_bit_) + 2) >> 2);
+ 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_bit_));
+ if (B7 < 0x80000000)
+ pressure = (B7 << 1) / B4;
+ else
+ pressure = (B7 / B4) << 1;
+
+ X1 = (pressure >> 8);
+ X1 *= X1;
+ X1 = (X1 * 3038) >>16;
+ X2 = (-7357 * pressure) >>16;
+ pressure += (X1 + X2 + 3791)>>4;
+
+ return pressure;
+}
+
+double BMP085::get_altitude_m()
+{
+ const double P0 = 1013.25; //pressure at sea level in hPa
+ double pres_hpa = pressure / 100.0;
+ altitude = 44330.0 * (1.0 - pow((pres_hpa/P0), 0.190295));
+ return altitude;
+}
+
+double BMP085::get_altitude_ft()
+{
+ return get_altitude_m()*3.28084;
+}
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