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Saturday 7 January 2012

MBED Example: How to use CMPS03 digital compass library

.from: http://mbed.org/users/aberk/libraries/CMPS03/liit1w

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/**
* @author Aaron Berk
*
* @section LICENSE
*
* Copyright (c) 2010 ARM Limited
*
* 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
*
* CMPS03 digital compass module.
*
* Datasheet:
*
* http://www.robot-electronics.co.uk/htm/cmps3tech.htm
*/

/**
* Includes
*/
#include "CMPS03.h"

CMPS03::CMPS03(PinName sda, PinName scl, int address) {

i2c = new I2C(sda, scl);
//Compass designed to work at 100KHz. See datasheet for details.
i2c->frequency(100000);
i2cAddress = address;

}

char CMPS03::readSoftwareRevision(void){

char registerNumber = SOFTWARE_REVISION_REG;
char registerContents = 0;

//First, send the number of register we wish to read,
//in this case, command register, number 0.
i2c->write(i2cAddress, ®isterNumber, 1);

//Now, read one byte, which will be the contents of the command register.
i2c->read(i2cAddress, ®isterContents, 1);

return registerContents;

}

int CMPS03::readBearing(void){

char registerNumber = COMPASS_BEARING_WORD_REG;
char registerContents[2] = {0x00, 0x00};

//First, send the number of register we wish to read,
//in this case, register numbers 2, 3, which hold the
//compass bearing as a 16-bit word.
i2c->write(i2cAddress, ®isterNumber, 1);

//Now read two bytes which will be the contents of
//these registers.
i2c->read(i2cAddress, registerContents, 2);

//Register 2 [read first], was the high byte, followed by
//register 3 [read second], which was the low byte.
int bearing = ((int)registerContents[0] << 8) | ((int)registerContents[1]);

return bearing;

}


XxXxXxXxXxXxXxXxXxXxXxXxXxXxXxXxXx CMPS03.h XxXxXxXxXxXxXxXxXxXxXxXxXxXxXxXxXx

/**
* @author Aaron Berk
*
* @section LICENSE
*
* Copyright (c) 2010 ARM Limited
*
* 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
*
* CMPS03 digital compass module.
*
* Datasheet:
*
* http://www.robot-electronics.co.uk/htm/cmps3tech.htm
*/

#ifndef CMPS03_H
#define CMPS03_H

/**
* Includes
*/
#include "mbed.h"

/**
* Defines
*/
#define CMPS03_DEFAULT_I2C_ADDRESS 0xC0

//-----------
// Registers
//-----------
#define SOFTWARE_REVISION_REG 0x0
#define COMPASS_BEARING_WORD_REG 0x2

/**
* CMPS03 digital compass module.
*/
class CMPS03 {

I2C* i2c;
int i2cAddress;

public:

/**
* Constructor.
*
* @param sda mbed pin to use for I2C SDA
* @param scl mbed pin to use for I2C SCL
* @param address I2C address of this device.
*/
CMPS03(PinName sda, PinName scl, int address);

/**
* Reads the software revision register [register 0] on the device.
*
* @return The contents of the software revision register as a byte.
*/
char readSoftwareRevision(void);

/**
* Reads the current bearing of the compass.
*
* @return The current bearing of the compass as a value between 0 and 3599,
* representing 0 - 359.9 degrees.
*/
int readBearing(void);

};

#endif /* CMPS03_H */


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