Alexandre Proulx / AccelSensor

YEah

Dependents:   I2C_Temp_sensor IR_Helicopter_Controller

Fork of AccelSensor by David Gronlund

AccelSensor.cpp@0:7dd118f48b1b, 2012-12-06 (annotated)

Committer:
dagronlund
Date:
Thu Dec 06 17:50:14 2012 +0000
Revision:
0:7dd118f48b1b
Child:
1:9e97f68b2654
First revision of mBed library for the Triple Axis Accelerometer Breakout - MMA8452Q from Sparkfun.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
dagronlund 0:7dd118f48b1b 1 #include "mbed.h"
dagronlund 0:7dd118f48b1b 2 #include "AccelSensor.h"
dagronlund 0:7dd118f48b1b 3
dagronlund 0:7dd118f48b1b 4 AccelSensor::AccelSensor(PinName sda, PinName scl) : _i2c(sda, scl) {
dagronlund 0:7dd118f48b1b 5 //No need to initialise anything else.
dagronlund 0:7dd118f48b1b 6 }
dagronlund 0:7dd118f48b1b 7
dagronlund 0:7dd118f48b1b 8 void AccelSensor::init() {
dagronlund 0:7dd118f48b1b 9 char c = readRegister(WHO_AM_I); // Read WHO_AM_I register
dagronlund 0:7dd118f48b1b 10 standby(); // Must be in standby to change registers
dagronlund 0:7dd118f48b1b 11 char scale = GSCALE; // Set up the full scale range to 2, 4, or 8g.
dagronlund 0:7dd118f48b1b 12 if (scale > 8) scale = 8; //Easy error check
dagronlund 0:7dd118f48b1b 13 scale >>= 2; // Neat trick, see page 22. 00 = 2G, 01 = 4G, 10 = 8G
dagronlund 0:7dd118f48b1b 14 writeRegister(XYZ_DATA_CFG, scale);
dagronlund 0:7dd118f48b1b 15 active(); // Set to active to start reading
dagronlund 0:7dd118f48b1b 16 }
dagronlund 0:7dd118f48b1b 17
dagronlund 0:7dd118f48b1b 18 void AccelSensor::standby() {
dagronlund 0:7dd118f48b1b 19 char c = readRegister(CTRL_REG1);
dagronlund 0:7dd118f48b1b 20 writeRegister(CTRL_REG1, c & ~(0x01)); //Clear the active bit to go into standby
dagronlund 0:7dd118f48b1b 21 }
dagronlund 0:7dd118f48b1b 22
dagronlund 0:7dd118f48b1b 23 void AccelSensor::active() {
dagronlund 0:7dd118f48b1b 24 char c = readRegister(CTRL_REG1);
dagronlund 0:7dd118f48b1b 25 writeRegister(CTRL_REG1, c | 0x01); //Set the active bit to begin detection
dagronlund 0:7dd118f48b1b 26 }
dagronlund 0:7dd118f48b1b 27
dagronlund 0:7dd118f48b1b 28 void AccelSensor::readData(int *destination) {
dagronlund 0:7dd118f48b1b 29 char rawData[6]; // x/y/z accel register data stored here
dagronlund 0:7dd118f48b1b 30 readRegisters(OUT_X_MSB, 6, rawData); // Read the six raw data registers into data array
dagronlund 0:7dd118f48b1b 31 // Loop to calculate 12-bit ADC and g value for each axis
dagronlund 0:7dd118f48b1b 32 for(int i = 0; i < 3 ; i++) {
dagronlund 0:7dd118f48b1b 33 int value = (rawData[i*2] << 8) | rawData[(i*2)+1]; //Combine the two 8 bit registers into one 12-bit number
dagronlund 0:7dd118f48b1b 34 value >>= 4; //The registers are left align, here we right align the 12-bit integer
dagronlund 0:7dd118f48b1b 35 // If the number is negative, we have to make it so manually (no 12-bit data type)
dagronlund 0:7dd118f48b1b 36 if (rawData[i*2] > 0x7F) {
dagronlund 0:7dd118f48b1b 37 value |= 0xFFFFF << 12;
dagronlund 0:7dd118f48b1b 38 }
dagronlund 0:7dd118f48b1b 39 destination[i] = value;
dagronlund 0:7dd118f48b1b 40 }
dagronlund 0:7dd118f48b1b 41 }
dagronlund 0:7dd118f48b1b 42
dagronlund 0:7dd118f48b1b 43 void AccelSensor::readRegisters(char reg, int range, char* dest) {
dagronlund 0:7dd118f48b1b 44 int ack = 0;
dagronlund 0:7dd118f48b1b 45 _i2c.start();
dagronlund 0:7dd118f48b1b 46 ack = _i2c.write((ADDRESS << 1));
dagronlund 0:7dd118f48b1b 47 ack = _i2c.write(reg);
dagronlund 0:7dd118f48b1b 48 _i2c.start();
dagronlund 0:7dd118f48b1b 49 ack = _i2c.write((ADDRESS << 1) | 0x01);
dagronlund 0:7dd118f48b1b 50 for (int i = 0; i < range - 1; i++) dest[i] = _i2c.read(1);
dagronlund 0:7dd118f48b1b 51 dest[range - 1] = _i2c.read(0);
dagronlund 0:7dd118f48b1b 52 _i2c.stop();
dagronlund 0:7dd118f48b1b 53 }
dagronlund 0:7dd118f48b1b 54
dagronlund 0:7dd118f48b1b 55 char AccelSensor::readRegister(char reg) {
dagronlund 0:7dd118f48b1b 56 int ack = 0;
dagronlund 0:7dd118f48b1b 57 _i2c.start();
dagronlund 0:7dd118f48b1b 58 ack = _i2c.write((ADDRESS << 1));
dagronlund 0:7dd118f48b1b 59 ack = _i2c.write(reg);
dagronlund 0:7dd118f48b1b 60 _i2c.start();
dagronlund 0:7dd118f48b1b 61 ack = _i2c.write((ADDRESS << 1) | 0x01);
dagronlund 0:7dd118f48b1b 62 char result = _i2c.read(0);
dagronlund 0:7dd118f48b1b 63 _i2c.stop();
dagronlund 0:7dd118f48b1b 64 return result;
dagronlund 0:7dd118f48b1b 65 }
dagronlund 0:7dd118f48b1b 66
dagronlund 0:7dd118f48b1b 67 void AccelSensor::writeRegister(char reg, char data) {
dagronlund 0:7dd118f48b1b 68 int ack = 0;
dagronlund 0:7dd118f48b1b 69 _i2c.start();
dagronlund 0:7dd118f48b1b 70 ack = _i2c.write((ADDRESS << 1));
dagronlund 0:7dd118f48b1b 71 ack = _i2c.write(reg);
dagronlund 0:7dd118f48b1b 72 ack = _i2c.write(data);
dagronlund 0:7dd118f48b1b 73 _i2c.stop();
dagronlund 0:7dd118f48b1b 74 }