Library for driving the MMA8452 accelerometer over I2C
Dependents: MMA8452_Test MMA8452_Demo Dualing_Tanks IMU-Controlled_MP3_Player ... more
Here is a simple example:
#include "mbed.h" #include "MMA8452.h" int main() { Serial pc(USBTX,USBRX); pc.baud(115200); double x = 0, y = 0, z = 0; MMA8452 acc(p28, p27, 40000); acc.setBitDepth(MMA8452::BIT_DEPTH_12); acc.setDynamicRange(MMA8452::DYNAMIC_RANGE_4G); acc.setDataRate(MMA8452::RATE_100); while(1) { if(!acc.isXYZReady()) { wait(0.01); continue; } acc.readXYZGravity(&x,&y,&z); pc.printf("Gravities: %lf %lf %lf\r\n",x,y,z); } }
An easy way to test that this actually works is to run the loop above and hold the MMA8452 parallel to the ground along the respective axis (and upsidedown in each axis). You will see 1G on the respective axis and 0G on the others.
Diff: MMA8452.cpp
- Revision:
- 20:d55e9d7eb17e
- Parent:
- 19:4d6cd7140a71
- Child:
- 21:a92a632a0cc7
--- a/MMA8452.cpp Thu Mar 06 18:07:43 2014 +0000 +++ b/MMA8452.cpp Fri Mar 07 11:55:30 2014 +0000 @@ -244,34 +244,51 @@ return 0; } -int readXCount(int *x) { +int MMA8452::readXCount(int *x) { char buf[2]; if(readXRaw((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::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::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 MMA8452::getCountsPerG() { + // assume starting with DYNAMIC_RANGE_2G and BIT_DEPTH_12 int countsPerG = 1024; if(_bitDepth==BIT_DEPTH_8) { countsPerG = 64; @@ -284,6 +301,15 @@ 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); @@ -291,6 +317,39 @@ 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;