MMA8451Q.h

00001 /* Copyright (c) 2010-2011 mbed.org, MIT License
00002 *
00003 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
00004 * and associated documentation files (the "Software"), to deal in the Software without
00005 * restriction, including without limitation the rights to use, copy, modify, merge, publish,
00006 * distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the
00007 * Software is furnished to do so, subject to the following conditions:
00008 *
00009 * The above copyright notice and this permission notice shall be included in all copies or
00010 * substantial portions of the Software.
00011 *
00012 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
00013 * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
00014 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
00015 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
00016 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
00017 */
00018 
00019 #ifndef MMA8451Q_H
00020 #define MMA8451Q_H
00021 
00022 #include "mbed.h"
00023 
00024 /**
00025 * MMA8451Q accelerometer example
00026 *
00027 * @code
00028 * #include "mbed.h"
00029 * #include "MMA8451Q.h"
00030 * 
00031 * #define MMA8451_I2C_ADDRESS (0x1d<<1)
00032 * 
00033 * int main(void) {
00034 * 
00035 * MMA8451Q acc(P_E25, P_E24, MMA8451_I2C_ADDRESS);
00036 * PwmOut rled(LED_RED);
00037 * PwmOut gled(LED_GREEN);
00038 * PwmOut bled(LED_BLUE);
00039 * 
00040 *     while (true) {       
00041 *         rled = 1.0 - abs(acc.getAccX());
00042 *         gled = 1.0 - abs(acc.getAccY());
00043 *         bled = 1.0 - abs(acc.getAccZ());
00044 *         wait(0.1);
00045 *     }
00046 * }
00047 * @endcode
00048 */
00049 class MMA8451Q
00050 {
00051 public:
00052   /**
00053   * MMA8451Q constructor
00054   *
00055   * @param sda SDA pin
00056   * @param sdl SCL pin
00057   * @param addr addr of the I2C peripheral
00058   */
00059   MMA8451Q(PinName sda, PinName scl, int addr);
00060 
00061   /**
00062   * MMA8451Q destructor
00063   */
00064   ~MMA8451Q();
00065   
00066   /**
00067   *  Reset the accelerometer hardware and set our initial parameters
00068   */
00069   void init();
00070 
00071   /**
00072    * Enter standby mode
00073    */
00074   void standby();
00075   
00076   /**
00077    * Enter active mode
00078    */
00079   void active();
00080   
00081   /**
00082    * Get the value of the WHO_AM_I register
00083    *
00084    * @returns WHO_AM_I value
00085    */
00086   uint8_t getWhoAmI();
00087 
00088   /**
00089    * Get X axis acceleration
00090    *
00091    * @returns X axis acceleration
00092    */
00093   float getAccX();
00094 
00095   /**
00096    * Get Y axis acceleration
00097    *
00098    * @returns Y axis acceleration
00099    */
00100   float getAccY();
00101   
00102   /**
00103    *  Read an X,Y pair
00104    */
00105   void getAccXY(float &x, float &y);
00106   
00107   /**
00108    *  Read X,Y,Z as floats.  This is the second most efficient way 
00109    *  to fetch all three axes (after the integer version), since it
00110    *  fetches all axes in a single I2C transaction.
00111    */
00112   void getAccXYZ(float &x, float &y, float &z);
00113   
00114   /**
00115    *  Read X,Y,Z as integers.  This reads the three axes in a single
00116    *  I2C transaction and returns them in the native integer scale,
00117    *  so it's the most efficient way to read the current 3D status.
00118    *  Each axis value is represented an an integer using the device's 
00119    *  native 14-bit scale, so each is in the range -8192..+8191.
00120    */
00121   void getAccXYZ(int &x, int &y, int &z);
00122 
00123   /**
00124    * Get Z axis acceleration
00125    *
00126    * @returns Z axis acceleration
00127    */
00128   float getAccZ();
00129 
00130   /**
00131    * Get XYZ axis acceleration
00132    *
00133    * @param res array where acceleration data will be stored
00134    */
00135   void getAccAllAxis(float * res);
00136   
00137   /**
00138    * Set interrupt mode.  'pin' is 1 for INT1_ACCEL (PTA14) and 2 for INT2_ACCEL (PTA15).
00139    * The caller is responsible for setting up an interrupt handler on the corresponding
00140    * PTAxx pin.
00141    */
00142   void setInterruptMode(int pin);
00143   
00144   /**
00145    * Set the hardware dynamic range, in G.  Valid ranges are 2, 4, and 8.
00146    */
00147   void setRange(int g);
00148   
00149   /**
00150    * Disable interrupts.
00151    */
00152   void clearInterruptMode();
00153   
00154   /**
00155    * Is a sample ready?
00156    */
00157   bool sampleReady();
00158   
00159   /**
00160    * Get the number of FIFO samples available
00161    */
00162   int getFIFOCount();
00163 
00164 private:
00165   I2C m_i2c;
00166   int m_addr;
00167   void readRegs(int addr, uint8_t * data, int len);
00168   void writeRegs(uint8_t * data, int len);
00169   int16_t getAccAxis(uint8_t addr);
00170   
00171   // Translate a 14-bit register value to a signed integer.  The
00172   // most significant 8 bits are in the first byte, and the least
00173   // significant 6 bits are in the second byte.  To adjust to a
00174   // regular integer, left-justify the 14 bits in an int16_t, then
00175   // divide by 4 to shift out the unused low two bits.  Note that
00176   // we have to divide rather than right-shift (>>) to ensure proper
00177   // filling of the sign bits.  The compiler should convert the
00178   // divide-by-4 to an arithmetic shift right by 2, so this should
00179   // still be efficient.
00180   inline int xlat14(const uint8_t *buf)
00181   {
00182       // Store the 16 bits left-justified in an int16_t, then cast
00183       // to a regular int to sign-extend to the full int width. 
00184       // Divide the result by 4 to shift out the unused 2 bits
00185       // at the right end.
00186       return int(int16_t((buf[0] << 8) | buf[1])) / 4;
00187   }
00188 
00189 };
00190 
00191 #endif