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accel.c
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accel.c
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// accel.c -- Accelerometer support
//
// Copyright (c) 2012-2013 Andrew Payne <andy@payne.org>
//
// Based on demo example from Freescale
#include <freedom.h>
#include "common.h"
#define MMA8451_I2C_ADDRESS (0x1d<<1)
#define I2C_READ 1
#define I2C_WRITE 0
#define I2C0_B I2C0_BASE_PTR
// ---------------------------------------------------------------------------
// I2C bus control functions
//
inline void i2c_set_tx(I2C_MemMapPtr p) {p->C1 |= I2C_C1_TX_MASK;}
inline void i2c_set_rx(I2C_MemMapPtr p) {p->C1 &= ~I2C_C1_TX_MASK;}
inline void i2c_set_slave(I2C_MemMapPtr p) {p->C1 &= ~I2C_C1_MST_MASK;}
inline void i2c_set_master(I2C_MemMapPtr p) {p->C1 |= I2C_C1_MST_MASK;}
inline void i2c_give_nack(I2C_MemMapPtr p) {p->C1 |= I2C_C1_TXAK_MASK;}
inline void i2c_give_ack(I2C_MemMapPtr p) {p->C1 &= ~I2C_C1_TXAK_MASK;}
inline void i2c_repeated_start(I2C_MemMapPtr p){p->C1 |= I2C_C1_RSTA_MASK;}
inline uint8_t i2c_read(I2C_MemMapPtr p) {return p->D;}
inline void i2c_start(I2C_MemMapPtr p)
{
i2c_set_master(p);
i2c_set_tx(p);
}
inline void i2c_stop(I2C_MemMapPtr p)
{
i2c_set_slave(p);
i2c_set_rx(p);
}
inline void i2c_wait(I2C_MemMapPtr p)
{
// Spin wait for the interrupt flag to be set
while((p->S & I2C_S_IICIF_MASK) == 0)
;
p->S |= I2C_S_IICIF_MASK; // Clear flag
}
inline int i2c_write(I2C_MemMapPtr p, uint8_t data)
{
// Send data, wait, and return ACK status
p->D = data;
i2c_wait(p);
return ((p->S & I2C_S_RXAK_MASK) == 0);
}
inline void i2c_init(I2C_MemMapPtr p)
{
// Enable clocks
SIM_SCGC5 |= SIM_SCGC5_PORTE_MASK;
SIM_SCGC4 |= SIM_SCGC4_I2C0_MASK;
// Configure GPIO for I2C
PORTE_PCR24 = PORT_PCR_MUX(5);
PORTE_PCR25 = PORT_PCR_MUX(5);
p->F = 0x14; // Baudrate settings: ICR=0x14, MULT=0
p->C1 = I2C_C1_IICEN_MASK; // Enable: IICEN=1
}
// ---------------------------------------------------------------------------
// MMA8451 control functions
//
uint8_t mma8451_read(uint8_t addr)
{
delay(1);
i2c_start(I2C0_B);
i2c_write(I2C0_B, MMA8451_I2C_ADDRESS | I2C_WRITE);
i2c_write(I2C0_B, addr);
i2c_repeated_start(I2C0_B);
i2c_write(I2C0_B, MMA8451_I2C_ADDRESS | I2C_READ);
i2c_set_rx(I2C0_B);
i2c_give_nack(I2C0_B);
i2c_read(I2C0_B);
i2c_wait(I2C0_B);
i2c_stop(I2C0_B);
return i2c_read(I2C0_B);
}
void mma8451_write(uint8_t addr, uint8_t data)
{
delay(1);
i2c_start(I2C0_B);
i2c_write(I2C0_B, MMA8451_I2C_ADDRESS | I2C_WRITE);
i2c_write(I2C0_B, addr);
i2c_write(I2C0_B, data);
i2c_stop(I2C0_B);
}
#define CTRL_REG1 (0x2a)
void accel_init(void)
{
uint8_t tmp;
i2c_init(I2C0_B);
tmp = mma8451_read(CTRL_REG1);
mma8451_write(CTRL_REG1, tmp | 0x01); // ACTIVE = 1
}
// Read a signed 14-bit value from (reg, reg+1)
int16_t _read_reg14(int reg)
{
return (int16_t)((mma8451_read(reg) << 8) | mma8451_read(reg+1)) >> 2;
}
// Read acceleration values for each axis
int16_t accel_x(void) {return _read_reg14(0x01);}
int16_t accel_y(void) {return _read_reg14(0x03);}
int16_t accel_z(void) {return _read_reg14(0x05);}