MMA8451Q.cpp

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 #include "MMA8451Q.h"
00020 
00021 #define REG_WHO_AM_I      0x0D
00022 #define REG_CTRL_REG_1    0x2A
00023 #define REG_OUT_X_MSB     0x01
00024 #define REG_OUT_Y_MSB     0x03
00025 #define REG_OUT_Z_MSB     0x05
00026 #define REG_XYZ_DATA_CFG  0x0E
00027 
00028 #define UINT14_MAX        16383
00029 
00030 MMA8451Q::MMA8451Q(PinName sda, PinName scl, int addr, uint8_t fsr) : m_i2c(sda, scl), m_addr(addr) {
00031     
00032     // Place the peripheral in standby mode to configure the full scale range
00033     uint8_t data[2] = {REG_CTRL_REG_1, 0x00};
00034     writeRegs(data, 2);
00035     
00036     // Set the scale
00037     setScale(fsr);
00038     
00039     // Activate the peripheral
00040     data[0] = REG_CTRL_REG_1;
00041     data[1] = 0x01;
00042     writeRegs(data, 2);
00043 }
00044 
00045 MMA8451Q::~MMA8451Q() { }
00046 
00047 uint8_t MMA8451Q::getWhoAmI() {
00048     uint8_t who_am_i = 0;
00049     readRegs(REG_WHO_AM_I, &who_am_i, 1);
00050     return who_am_i;
00051 }
00052 
00053 float MMA8451Q::getAccX() {
00054     return (float(getAccAxis(REG_OUT_X_MSB))/4096.0);
00055 }
00056 
00057 float MMA8451Q::getAccY() {
00058     return (float(getAccAxis(REG_OUT_Y_MSB))/4096.0);
00059 }
00060 
00061 float MMA8451Q::getAccZ() {
00062     return (float(getAccAxis(REG_OUT_Z_MSB))/4096.0);
00063 }
00064 
00065 void MMA8451Q::getAccAllAxis(float * res) {
00066     res[0] = getAccX();
00067     res[1] = getAccY();
00068     res[2] = getAccZ();
00069 }
00070 
00071 int16_t MMA8451Q::getAccAxis(uint8_t addr) {
00072     int16_t acc;
00073     uint8_t res[2];
00074     readRegs(addr, res, 2);
00075 
00076     acc = (res[0] << 6) | (res[1] >> 2);
00077     if (acc > UINT14_MAX/2)
00078         acc -= UINT14_MAX;
00079 
00080     return acc;
00081 }
00082 
00083 void MMA8451Q::setScale(uint8_t fsr)
00084 {
00085     // Read register
00086     uint8_t cfg;
00087     readRegs(REG_XYZ_DATA_CFG, &cfg, 8);
00088     
00089     // Mask out scale bits
00090     cfg = cfg & 0xFC;
00091     cfg = cfg | fsr;  // Neat trick, see page 22. 00 = 2G, 01 = 4A, 10 = 8G
00092     
00093     // Write the configuration register
00094     uint8_t data[2] = {REG_XYZ_DATA_CFG, cfg};
00095     writeRegs(data, 8);
00096 }
00097 
00098 uint8_t MMA8451Q::Read_Status()
00099 {
00100     uint8_t Status;
00101     readRegs(0, &Status, 1);
00102     return Status;
00103 }
00104 
00105 void MMA8451Q::readRegs(int addr, uint8_t * data, int len) {
00106     char t[1] = {addr};
00107     m_i2c.write(m_addr, t, 1, true);
00108     m_i2c.read(m_addr, (char *)data, len);
00109 }
00110 
00111 void MMA8451Q::writeRegs(uint8_t * data, int len) {
00112     m_i2c.write(m_addr, (char *)data, len);
00113 }