Diff: MMA8452.cpp

Revision:

0:4c644bb83761

diff -r 000000000000 -r 4c644bb83761 MMA8452.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/MMA8452.cpp	Sun Apr 21 15:48:44 2019 +0000
@@ -0,0 +1,538 @@
+// Authors: Ashley Mills, Nicholas Herriot
+/* Copyright (c) 2013 Vodafone, MIT 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.
+ */
+
+#include "MMA8452.h"
+#include "mbed.h"
+
+#ifdef MMA8452_DEBUG
+// you need to define Serial pc(USBTX,USBRX) somewhere for the below line to make sense
+extern Serial pc;
+#define MMA8452_DBG(...) pc.printf(__VA_ARGS__); pc.printf("\r\n");
+#else
+#define MMA8452_DBG(...)
+#endif
+
+// Connect module at I2C address using I2C port pins sda and scl
+MMA8452::MMA8452(PinName sda, PinName scl, int frequency) : _i2c(sda, scl) , _frequency(frequency) {
+   MMA8452_DBG("Creating MMA8452");
+   
+   // set I2C frequency
+   _i2c.frequency(_frequency);
+   
+   // setup read and write addresses for convenience
+   _readAddress   = MMA8452_ADDRESS | 0x01;
+   _writeAddress  = MMA8452_ADDRESS & 0xFE;
+   
+   // set some defaults
+   _bitDepth = BIT_DEPTH_UNKNOWN;
+   setBitDepth(BIT_DEPTH_12);
+   _dynamicRange = DYNAMIC_RANGE_UNKNOWN;
+   setDynamicRange(DYNAMIC_RANGE_2G);
+   
+   MMA8452_DBG("Done");
+}
+
+
+// Destroys instance
+MMA8452::~MMA8452() {}
+
+// Setting the control register bit 1 to true to activate the MMA8452
+int MMA8452::activate() {
+    // perform write and return error code
+    return logicalORRegister(MMA8452_CTRL_REG_1,MMA8452_ACTIVE_MASK);
+}
+
+// Setting the control register bit 1 to 0 to standby the MMA8452
+int MMA8452::standby() {
+    // perform write and return error code
+    return logicalANDRegister(MMA8452_CTRL_REG_1,MMA8452_STANDBY_MASK);
+}
+
+// this reads a register, applies a bitmask with logical AND, sets a value with logical OR,
+// and optionally goes into and out of standby at the beginning and end of the function respectively
+int MMA8452::maskAndApplyRegister(char reg, char mask, char value, int toggleActivation) {
+   if(toggleActivation) {
+       if(standby()) {
+          return 1;
+       }
+   }
+   
+   // read from register
+   char oldValue = 0;
+   if(readRegister(reg,&oldValue)) {
+      return 1;
+   }
+   
+   // apply bitmask
+   oldValue &= mask;
+   
+   // set value
+   oldValue |= value;
+   
+   // write back to register
+   if(writeRegister(reg,oldValue)) {
+      return 1;
+   }
+   
+   if(toggleActivation) {
+       if(activate()) {
+          return 1;
+       }
+   }
+   return 0;
+}
+
+int MMA8452::setDynamicRange(DynamicRange range, int toggleActivation) {
+   _dynamicRange = range;
+   return maskAndApplyRegister(
+      MMA8452_XYZ_DATA_CFG,
+      MMA8452_DYNAMIC_RANGE_MASK,
+      range,
+      toggleActivation
+   );
+}
+
+int MMA8452::setDataRate(DataRateHz dataRate, int toggleActivation) {
+   return maskAndApplyRegister(
+       MMA8452_CTRL_REG_1,
+       MMA8452_DATA_RATE_MASK,
+       dataRate<<MMA8452_DATA_RATE_MASK_SHIFT,
+       toggleActivation
+   );
+}
+
+int MMA8452::setBitDepth(BitDepth depth,int toggleActivation) {
+   _bitDepth = depth;
+   return maskAndApplyRegister(
+      MMA8452_CTRL_REG_1,
+      MMA8452_BIT_DEPTH_MASK,
+      depth<<MMA8452_BIT_DEPTH_MASK_SHIFT,
+      toggleActivation
+   );
+}
+
+char MMA8452::getMaskedRegister(int addr, char mask) {
+   char rval = 0;
+   if(readRegister(addr,&rval)) {
+      return 0;
+   }
+   return (rval&mask);
+}
+
+int MMA8452::isXYZReady() {
+   return getMaskedRegister(MMA8452_STATUS,MMA8452_STATUS_ZYXDR_MASK)>0;
+}
+
+int MMA8452::isXReady() {
+   return getMaskedRegister(MMA8452_STATUS,MMA8452_STATUS_XDR_MASK)>0;
+}
+
+int MMA8452::isYReady() {
+   return getMaskedRegister(MMA8452_STATUS,MMA8452_STATUS_YDR_MASK)>0;
+}
+
+int MMA8452::isZReady() {
+   return getMaskedRegister(MMA8452_STATUS,MMA8452_STATUS_ZDR_MASK)>0;
+}
+
+
+int MMA8452::getDeviceID(char *dst) {
+   return readRegister(MMA8452_WHO_AM_I,dst);
+}
+
+int MMA8452::getStatus(char* dst) {
+   return readRegister(MMA8452_STATUS,dst);
+}
+
+MMA8452::DynamicRange MMA8452::getDynamicRange() {
+   char rval = 0;
+   if(readRegister(MMA8452_XYZ_DATA_CFG,&rval)) {
+      return MMA8452::DYNAMIC_RANGE_UNKNOWN;
+   }
+   rval &= (MMA8452_DYNAMIC_RANGE_MASK^0xFF);
+   return (MMA8452::DynamicRange)rval;
+}
+
+MMA8452::DataRateHz MMA8452::getDataRate() {
+   char rval = 0;
+   if(readRegister(MMA8452_CTRL_REG_1,&rval)) {
+      return MMA8452::RATE_UNKNOWN;
+   }
+   // logical AND with inverse of mask
+   rval = rval&(MMA8452_DATA_RATE_MASK^0xFF);
+   // shift back into position
+   rval >>= MMA8452_DATA_RATE_MASK_SHIFT;
+   return (MMA8452::DataRateHz)rval;
+}
+
+// Reads xyz
+int MMA8452::readXYZRaw(char *dst) {
+   if(_bitDepth==BIT_DEPTH_UNKNOWN) {
+      return 1;
+   }
+   int readLen = 3;
+   if(_bitDepth==BIT_DEPTH_12) {
+      readLen = 6;
+   }
+   return readRegister(MMA8452_OUT_X_MSB,dst,readLen);
+}
+
+int MMA8452::readXRaw(char *dst) {
+   if(_bitDepth==BIT_DEPTH_UNKNOWN) {
+      return 1;
+   }
+   int readLen = 1;
+   if(_bitDepth==BIT_DEPTH_12) {
+      readLen = 2;
+   }
+   return readRegister(MMA8452_OUT_X_MSB,dst,readLen);
+}
+
+int MMA8452::readYRaw(char *dst) {
+   if(_bitDepth==BIT_DEPTH_UNKNOWN) {
+      return 1;
+   }
+   int readLen = 1;
+   if(_bitDepth==BIT_DEPTH_12) {
+      readLen = 2;
+   }
+   return readRegister(MMA8452_OUT_Y_MSB,dst,readLen);
+}
+
+int MMA8452::readZRaw(char *dst) {
+   if(_bitDepth==BIT_DEPTH_UNKNOWN) {
+      return 1;
+   }
+   int readLen = 1;
+   if(_bitDepth==BIT_DEPTH_12) {
+      readLen = 2;
+   }
+   return readRegister(MMA8452_OUT_Z_MSB,dst,readLen);
+}
+
+int MMA8452::readXYZCounts(int *x, int *y, int *z) {
+   char buf[6];
+   if(readXYZRaw((char*)&buf)) {
+       return 1;
+   }
+   if(_bitDepth==BIT_DEPTH_12) {
+     *x = twelveBitToSigned(&buf[0]);
+     *y = twelveBitToSigned(&buf[2]);
+     *z = twelveBitToSigned(&buf[4]);
+   } else {
+     *x = eightBitToSigned(&buf[0]);
+     *y = eightBitToSigned(&buf[1]);
+     *z = eightBitToSigned(&buf[2]);
+   }
+   
+   return 0;
+}
+
+int MMA8452::readXCount(int *x) {
+   char buf[2];
+   if(readXRaw((char*)&buf)) {
+       return 1;
+   }
+   if(_bitDepth==BIT_DEPTH_12) {
+     *x = twelveBitToSigned(&buf[0]);
+   } else {
+     *x = eightBitToSigned(&buf[0]);
+   }
+   return 0;
+}
+
+int MMA8452::readYCount(int *y) {
+   char buf[2];
+   if(readYRaw((char*)&buf)) {
+       return 1;
+   }
+   if(_bitDepth==BIT_DEPTH_12) {
+     *y = twelveBitToSigned(&buf[0]);
+   } else {
+     *y = eightBitToSigned(&buf[0]);
+   }
+   return 0;
+}
+
+int MMA8452::readZCount(int *z) {
+   char buf[2];
+   if(readZRaw((char*)&buf)) {
+       return 1;
+   }
+   if(_bitDepth==BIT_DEPTH_12) {
+     *z = twelveBitToSigned(&buf[0]);
+   } else {
+     *z = eightBitToSigned(&buf[0]);
+   }
+   return 0;
+}
+
+double MMA8452::convertCountToGravity(int count, int countsPerG) {
+   return (double)count/(double)countsPerG;
+}
+
+int MMA8452::getCountsPerG() {
+ // assume starting with DYNAMIC_RANGE_2G and BIT_DEPTH_12
+   int countsPerG = 1024;
+   if(_bitDepth==BIT_DEPTH_8) {
+      countsPerG = 64;
+   }
+   switch(_dynamicRange) {
+      case DYNAMIC_RANGE_4G:
+         countsPerG /= 2;
+      break;
+      case DYNAMIC_RANGE_8G:
+         countsPerG /= 4;
+      break;
+   }
+   return countsPerG;
+}
+
+int MMA8452::readXYZGravity(double *x, double *y, double *z) {
+   int xCount = 0, yCount = 0, zCount = 0;
+   if(readXYZCounts(&xCount,&yCount,&zCount)) {
+      return 1;
+   }
+   int countsPerG = getCountsPerG();
+   
+   *x = convertCountToGravity(xCount,countsPerG);
+   *y = convertCountToGravity(yCount,countsPerG);
+   *z = convertCountToGravity(zCount,countsPerG);
+   return 0;
+}
+
+int MMA8452::readXGravity(double *x) {
+   int xCount = 0;
+   if(readXCount(&xCount)) {
+      return 1;
+   }
+   int countsPerG = getCountsPerG();
+   
+   *x = convertCountToGravity(xCount,countsPerG);
+   return 0;
+}
+
+int MMA8452::readYGravity(double *y) {
+   int yCount = 0;
+   if(readYCount(&yCount)) {
+      return 1;
+   }
+   int countsPerG = getCountsPerG();
+   
+   *y = convertCountToGravity(yCount,countsPerG);
+   return 0;
+}
+
+int MMA8452::readZGravity(double *z) {
+   int zCount = 0;
+   if(readZCount(&zCount)) {
+      return 1;
+   }
+   int countsPerG = getCountsPerG();
+   
+   *z = convertCountToGravity(zCount,countsPerG);
+   return 0;
+}
+
+// apply an AND mask to a register. read register value, apply mask, write it back
+int MMA8452::logicalANDRegister(char addr, char mask) {
+   char value = 0;
+   // read register value
+   if(readRegister(addr,&value)) {
+      return 0;
+   }
+   // apply mask
+   value &= mask;
+   return writeRegister(addr,value);
+}
+
+
+// apply an OR mask to a register. read register value, apply mask, write it back
+int MMA8452::logicalORRegister(char addr, char mask) {
+   char value = 0;
+   // read register value
+   if(readRegister(addr,&value)) {
+      return 0;
+   }
+   // apply mask
+   value |= mask;
+   return writeRegister(addr,value);
+}
+
+// apply an OR mask to a register. read register value, apply mask, write it back
+int MMA8452::logicalXORRegister(char addr, char mask) {
+   char value = 0;
+   // read register value
+   if(readRegister(addr,&value)) {
+      return 0;
+   }
+   // apply mask
+   value ^= mask;
+   return writeRegister(addr,value);
+}
+
+// Write register (The device must be placed in Standby Mode to change the value of the registers) 
+int MMA8452::writeRegister(char addr, char data) {
+    // what this actually does is the following
+    // 1. tell I2C bus to start transaction
+    // 2. tell slave we want to write (slave address & write flag)
+    // 3. send the write address
+    // 4. send the data to write
+    // 5. tell I2C bus to end transaction
+
+    // we can wrap this up in the I2C library write function
+    char buf[2] = {0,0};
+    buf[0] = addr;
+    buf[1] = data;
+    return _i2c.write(MMA8452_ADDRESS, buf,2);
+    // note, could also do return writeRegister(addr,&data,1);
+}
+
+int MMA8452::eightBitToSigned(char *buf) {
+   return (int8_t)*buf;
+}
+
+int MMA8452::twelveBitToSigned(char *buf) {
+   // cheat by using the int16_t internal type
+   // all we need to do is convert to little-endian format and shift right
+   int16_t x = 0;
+   ((char*)&x)[1] = buf[0];
+   ((char*)&x)[0] = buf[1];
+   // note this only works because the below is an arithmetic right shift
+   return x>>4; 
+}
+
+int MMA8452::writeRegister(char addr, char *data, int nbytes) {
+    // writing multiple bytes is a little bit annoying because
+    // the I2C library doesn't support sending the address separately
+    // so we just do it manually
+    
+    // 1. tell I2C bus to start transaction
+    _i2c.start();
+    // 2. tell slave we want to write (slave address & write flag)
+    if(_i2c.write(_writeAddress)!=1) {
+       return 1;
+    }
+    // 3. send the write address
+    if(_i2c.write(addr)!=1) {
+       return 1;
+    }
+    // 4. send the data to write
+    for(int i=0; i<nbytes; i++) {
+       if(_i2c.write(data[i])!=1) {
+          return 1;
+       }
+    }
+    // 5. tell I2C bus to end transaction
+    _i2c.stop();
+    return 0;
+}
+
+int MMA8452::readRegister(char addr, char *dst, int nbytes) {
+    // this is a bit odd, but basically proceeds like this
+    // 1. Send a start command
+    // 2. Tell the slave we want to write (slave address & write flag)
+    // 3. Send the address of the register (addr)
+    // 4. Send another start command to delineate read portion
+    // 5. Tell the slave we want to read (slave address & read flag)
+    // 6. Read the register value bytes
+    // 7. Send a stop command
+    
+    // we can wrap this process in the I2C library read and write commands
+    if(_i2c.write(MMA8452_ADDRESS,&addr,1,true)) {
+       return 1;
+    }
+    return _i2c.read(MMA8452_ADDRESS,dst,nbytes);
+}
+
+// most registers are 1 byte, so here is a convenience function
+int MMA8452::readRegister(char addr, char *dst) {
+    return readRegister(addr,dst,1);
+}
+
+MMA8452::BitDepth MMA8452::getBitDepth() {
+   return _bitDepth;
+}
+
+#ifdef MMA8452_DEBUG
+void MMA8452::debugRegister(char reg) {
+   // get register value
+   char v = 0;
+   if(readRegister(reg,&v)) {
+      MMA8452_DBG("Error reading specified register");
+      return;
+   }
+   // print out details
+   switch(reg) {
+      case MMA8452_CTRL_REG_1:
+         MMA8452_DBG("CTRL_REG_1 has value: 0x%x",v);
+         MMA8452_DBG(" 7  ALSP_RATE_1: %d",(v&0x80)>>7);
+         MMA8452_DBG(" 6  ALSP_RATE_0: %d",(v&0x40)>>6);
+         MMA8452_DBG(" 5  DR2: %d",        (v&0x20)>>5);
+         MMA8452_DBG(" 4  DR1: %d",        (v&0x10)>>4);
+         MMA8452_DBG(" 3  DR0: %d",        (v&0x08)>>3);
+         MMA8452_DBG(" 2  LNOISE: %d",     (v&0x04)>>2);
+         MMA8452_DBG(" 1  FREAD: %d",      (v&0x02)>>1);
+         MMA8452_DBG(" 0  ACTIVE: %d",     (v&0x01));
+      break;
+        
+      case MMA8452_XYZ_DATA_CFG:
+         MMA8452_DBG("XYZ_DATA_CFG has value: 0x%x",v);
+         MMA8452_DBG(" 7  Unused: %d", (v&0x80)>>7);
+         MMA8452_DBG(" 6  0: %d",      (v&0x40)>>6);
+         MMA8452_DBG(" 5  0: %d",      (v&0x20)>>5);
+         MMA8452_DBG(" 4  HPF_Out: %d",(v&0x10)>>4);
+         MMA8452_DBG(" 3  0: %d",      (v&0x08)>>3);
+         MMA8452_DBG(" 2  0: %d",      (v&0x04)>>2);
+         MMA8452_DBG(" 1  FS1: %d",    (v&0x02)>>1);
+         MMA8452_DBG(" 0  FS0: %d",    (v&0x01));
+         switch(v&0x03) {
+            case 0:
+               MMA8452_DBG("Dynamic range: 2G");
+            break;
+            case 1:
+               MMA8452_DBG("Dynamic range: 4G");
+            break;
+            case 2:
+               MMA8452_DBG("Dynamic range: 8G");
+            break;
+            default:
+               MMA8452_DBG("Unknown dynamic range");
+            break;
+         }
+      break;
+      
+      case MMA8452_STATUS:
+         MMA8452_DBG("STATUS has value: 0x%x",v);
+         MMA8452_DBG(" 7  ZYXOW: %d",(v&0x80)>>7);
+         MMA8452_DBG(" 6  ZOW: %d",  (v&0x40)>>6);
+         MMA8452_DBG(" 5  YOW: %d",  (v&0x20)>>5);
+         MMA8452_DBG(" 4  XOW: %d",  (v&0x10)>>4);
+         MMA8452_DBG(" 3  ZYXDR: %d",(v&0x08)>>3);
+         MMA8452_DBG(" 2  ZDR: %d",  (v&0x04)>>2);
+         MMA8452_DBG(" 1  YDR: %d",  (v&0x02)>>1);
+         MMA8452_DBG(" 0  XDR: %d",  (v&0x01));
+      break;
+      
+      default:
+         MMA8452_DBG("Unknown register address: 0x%x",reg);
+      break;
+   }
+}
+#endif
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