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Diff: MMA8452.cpp
- Revision:
- 13:4bd8b4cd479d
- Parent:
- 12:172540ff6b8b
- Child:
- 14:0602b45ca70f
diff -r 172540ff6b8b -r 4bd8b4cd479d MMA8452.cpp --- a/MMA8452.cpp Tue Mar 04 17:50:47 2014 +0000 +++ b/MMA8452.cpp Wed Mar 05 15:04:13 2014 +0000 @@ -36,6 +36,9 @@ // set some defaults _bitDepth = BIT_DEPTH_UNKNOWN; setBitDepth(BIT_DEPTH_12); + _dynamicRange = DYNAMIC_RANGE_UNKNOWN; + setDynamicRange(DYNAMIC_RANGE_2G); + DBG("Done"); } @@ -90,6 +93,7 @@ } int MMA8452::setDynamicRange(DynamicRange range, int toggleActivation) { + _dynamicRange = range; return maskAndApplyRegister( MMA8452_XYZ_DATA_CFG, MMA8452_DYNAMIC_RANGE_MASK, @@ -155,7 +159,7 @@ } // Reads xyz -int MMA8452::readRawXYZ(char *dst) { +int MMA8452::readXYZRaw(char *dst) { if(_bitDepth==BIT_DEPTH_UNKNOWN) { return 1; } @@ -166,6 +170,54 @@ return readRegister(MMA8452_OUT_X_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; +} + +double MMA8452::convertCountToGravity(int count, int countsPerG) { + return (double)count/(double)countsPerG; +} + +int MMA8452::readXYZGravity(double *x, double *y, double *z) { + int xCount = 0, yCount = 0, zCount = 0; + if(readXYZCounts(&xCount,&yCount,&zCount)) { + return 1; + } + + // 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; + } + + *x = convertCountToGravity(xCount,countsPerG); + *y = convertCountToGravity(yCount,countsPerG); + *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; @@ -220,6 +272,19 @@ // 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