srf02.c
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/*
* Copyright (C) 2013 Zakaria Kasmi <zkasmi@inf.fu-berlin.de>
* 2015 Freie Universität Berlin
*
* This file is subject to the terms and conditions of the GNU Lesser General
* Public License v2.1. See the file LICENSE in the top level directory for more
* details.
*/
/**
* @ingroup driver_srf02
* @{
*
* @file
* @brief Driver for the SRF02 ultrasonic range sensor
*
* @author Zakaria Kasmi <zkasmi@inf.fu-berlin.de>
* @author Peter Kietzmann <peter.kietzmann@haw-hamburg.de>
* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
*
* @}
*/
#include <stdint.h>
#include <stdio.h>
#include "xtimer.h"
#include "srf02.h"
#include "periph/i2c.h"
#define ENABLE_DEBUG (0)
#include "debug.h"
/**
* @brief Per default use normal speed on the I2C bus
*/
#define BUS_SPEED (I2C_SPEED_NORMAL)
/**
* @brief SRF02 register addresses
* @{
*/
#define REG_CMD (0x00)
#define REG_HIGH (0x02)
#define REG_LOW (0x03)
#define REG_AUTO_HIGH (0x04)
#define REG_AUTO_LOW (0x05)
/** @} */
/**
* @brief Some additional SRF02 commands
* @{
*/
#define CMD_ADDR_SEQ1 (0xa0)
#define CMD_ADDR_SEQ2 (0xaa)
#define CMD_ADDR_SEQ3 (0xa5)
/** @} */
int srf02_init(srf02_t *dev, i2c_t i2c, uint8_t addr)
{
dev->i2c = i2c;
dev->addr = (addr >> 1); /* internally we right align the 7-bit addr */
uint8_t rev;
/* Acquire exclusive access to the bus. */
i2c_acquire(dev->i2c);
/* initialize i2c interface */
if (i2c_init_master(dev->i2c, BUS_SPEED) < 0) {
DEBUG("[srf02] error initializing I2C bus\n");
return -1;
}
/* try to read the software revision (read the CMD reg) from the device */
i2c_read_reg(i2c, dev->addr, REG_CMD, &rev);
if (rev == 0 || rev == 255) {
i2c_release(dev->i2c);
DEBUG("[srf02] error reading the devices software revision\n");
return -1;
} else {
DEBUG("[srf02] software revision: 0x%02x\n", rev);
}
/* Release the bus for other threads. */
i2c_release(dev->i2c);
DEBUG("[srf02] initialization successful\n");
return 0;
}
void srf02_trigger(srf02_t *dev, srf02_mode_t mode)
{
/* trigger a new measurement by writing the mode to the CMD register */
DEBUG("[srf02] trigger new reading\n");
i2c_acquire(dev->i2c);
i2c_write_reg(dev->i2c, dev->addr, REG_CMD, mode);
i2c_release(dev->i2c);
}
uint16_t srf02_read(srf02_t *dev)
{
uint8_t res[2];
/* read the results */
i2c_acquire(dev->i2c);
i2c_read_regs(dev->i2c, dev->addr, REG_HIGH, res, 2);
i2c_release(dev->i2c);
DEBUG("[srf02] result - high: 0x%02x low: 0x%02x\n", res[0], res[1]);
/* compile result - TODO: fix for different host byte order other than LE */
return ((((uint16_t)res[0]) << 8) | (res[1] & 0xff));
}
uint16_t srf02_get_distance(srf02_t *dev, srf02_mode_t mode)
{
/* trigger a new reading */
srf02_trigger(dev, mode);
/* give the sensor the required time for sampling */
xtimer_usleep(SRF02_RANGE_DELAY);
/* get the results */
return srf02_read(dev);
}
void srf02_set_addr(srf02_t *dev, uint8_t new_addr)
{
/* get access to the bus */
i2c_acquire(dev->i2c);
DEBUG("[srf02] reprogramming device address to 0x%02x\n", (int)new_addr);
/* write the new address, for this we need to follow a certain sequence */
i2c_write_reg(dev->i2c, dev->addr, REG_CMD, CMD_ADDR_SEQ1);
i2c_write_reg(dev->i2c, dev->addr, REG_CMD, CMD_ADDR_SEQ2);
i2c_write_reg(dev->i2c, dev->addr, REG_CMD, CMD_ADDR_SEQ3);
i2c_write_reg(dev->i2c, dev->addr, REG_CMD, new_addr);
dev->addr = (new_addr >> 1);
/* release the bus */
i2c_release(dev->i2c);
}