From d99aaff2fbe4bea541428c600fc68af33846ebdc Mon Sep 17 00:00:00 2001
From: Hauke Petersen <hauke.petersen@fu-berlin.de>
Date: Fri, 4 Sep 2015 18:45:32 +0200
Subject: [PATCH] drivers/srf02: various optimizations
- switched to use xtimer
- simplified interface slightly
- optimized reading of results
- some style cleanups
- updated the documentation
---
Makefile.dep | 4 ++
drivers/include/srf02.h | 64 ++++++++++---------------
drivers/srf02/srf02.c | 101 +++++++++++++++++++++-------------------
3 files changed, 81 insertions(+), 88 deletions(-)
diff --git a/Makefile.dep b/Makefile.dep
index 5ba1a10e5d..e5239c3a49 100644
--- a/Makefile.dep
+++ b/Makefile.dep
@@ -279,3 +279,7 @@ ifneq (,$(filter encx24j600,$(USEMODULE)))
USEMODULE += timex
USEMODULE += vtimer
endif
+
+ifneq (,$(filter srf02,$(USEMODULE)))
+ USEMODULE += xtimer
+endif
diff --git a/drivers/include/srf02.h b/drivers/include/srf02.h
index d47245bc5f..c7065aaa2e 100644
--- a/drivers/include/srf02.h
+++ b/drivers/include/srf02.h
@@ -1,5 +1,6 @@
/*
* 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
@@ -7,27 +8,22 @@
*/
/**
- * @defgroup driver_srf02 SRF02 ultrasonic range sensor
+ * @defgroup driver_srf02 SRF02
* @ingroup drivers
* @brief Driver for the SRF02 ultrasonic range sensor
- *
- * The connection between the MCU and the SRF02 is based on the i2c-interface.
- *
* @{
*
* @file
* @brief Driver definitions for the SRF02 ultrasonic ranger.
*
- * The connection between the SRF02 and the MCU is based on the i2c interface.
- *
* @author Zakaria Kasmi <zkasmi@inf.fu-berlin.de>
* @author Peter Kietzmann <peter.kietzmann@haw-hamburg.de>
+ * @author Hauke Petersen <hauke.petersen@fu-berlin.de>
*/
#ifndef SRF02_H_
#define SRF02_H_
-
#include <stdint.h>
#include "periph/i2c.h"
@@ -35,20 +31,13 @@
extern "C" {
#endif
-/** @brief The sensors default I2C address */
+/**
+ * @brief Default I2C address of SRF02 sensors
+ */
#define SRF02_DEFAULT_ADDR 112
-/** @brief The command register which defines measurement mode */
-#define SRF02_COMMAND_REG 0x0
-
-/** @brief The upper measurement byte */
-#define SRF02_RANGE_HIGH_BYTE 0x2
-
-/** @brief The lower measurement byte */
-#define SRF02_RANGE_LOW_BYTE 0x3
-
/**
- * @brief Device descriptor for SRF02 sensors
+ * @brief Device descriptor for SRF02 sensors
*/
typedef struct {
i2c_t i2c; /**< I2C device the sensor is connected to */
@@ -56,45 +45,42 @@ typedef struct {
} srf02_t;
/**
- * @brief Possible measurement modes for the SRF02 sensor
+ * @brief Possible measurement modes of the SRF02 sensor
*/
typedef enum {
- SRF02_MODE_REAL_INCH = 0x50, /**< result in inches */
- SRF02_MODE_REAL_CM = 0x51, /**< result in centimeters */
- SRF02_REAL_RANGING_MODE_MICRO_SEC = 0x52, /**< result in microseconds */
- SRF02_FAKE_RANGING_MODE_INCH = 0x56, /**< synchronous measurement in inches */
- SRF02_FAKE_RANGING_MODE_CM = 0x57, /**< synchronous measurement in centimeters */
- SRF02_FAKE_RANGING_MODE_MICRO_SEC = 0x58 /**< synchronous measurement in microseconds */
-}srf02_mode_t;
+ SRF02_MODE_REAL_INCH = 0x50, /**< result in inches */
+ SRF02_MODE_REAL_CM = 0x51, /**< result in centimeters */
+ SRF02_MODE_REAL_MS = 0x52, /**< result in microseconds */
+ SRF02_MODE_FAKE_INCH = 0x56, /**< result in inches (no pulse send) */
+ SRF02_MODE_FAKE_CM = 0x57, /**< result in cm (no pulse send) */
+ SRF02_MODE_FAKE_MS = 0x58 /**< result in ms (no pulse send) */
+} srf02_mode_t;
/**
- * @brief Initialize the SRF02 ultrasonic sensor
+ * @brief Initialize the SRF02 ultrasonic sensor
*
* @param[in] dev device descriptor of an SRF02 sensor
* @param[in] i2c I2C device the sensor is connected to
* @param[in] addr I2C address of the sensor
- * @param[in] speed I2C speed mode
*
* @return 0 on successful initialization
- * @return -1 on undefined device given
- * @return -2 on unsupported speed value
+ * @return -1 on error
*/
-int srf02_init(srf02_t *dev, i2c_t i2c, uint8_t addr, i2c_speed_t speed);
+int srf02_init(srf02_t *dev, i2c_t i2c, uint8_t addr);
/**
- * @brief Get the distance measured from the SRF02 ultrasonic sensor
- * The result of a ranging can be returned in inches,
- * centimeters or microseconds
+ * @brief Get the distance measured from the SRF02 ultrasonic sensor
+ *
+ * The result of the ranging operation is returned in inches, centimeters or
+ * microseconds - depending on the given @p mode parameter.
+ *
* @param[in] dev device descriptor of an SRF02 sensor
* @param[in] mode there are three real ranging modes, which return
* the result in inches, centimeters or microseconds.
* Another set of three fake ranging modes do the same
* but without transmitting the burst
*
- * @return -1 on undefined device given
- * @return the ranging result in inches, centimeters or microseconds. In the
- * case of the fake ranging mode a zero value is returned. UINT16_MAX
- * is returned if write/read action from the i2c-interface is failed.
+ * @return the ranging result in inches, centimeters or microseconds
*
*/
uint16_t srf02_get_distance(srf02_t *dev, srf02_mode_t mode);
@@ -103,5 +89,5 @@ uint16_t srf02_get_distance(srf02_t *dev, srf02_mode_t mode);
}
#endif
-/** @} */
#endif /* SRF02_H_ */
+/** @} */
diff --git a/drivers/srf02/srf02.c b/drivers/srf02/srf02.c
index 6994ceb9f4..953cdd7cf7 100644
--- a/drivers/srf02/srf02.c
+++ b/drivers/srf02/srf02.c
@@ -1,5 +1,6 @@
/*
* 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
@@ -11,91 +12,93 @@
* @{
*
* @file
- * @brief Driver for the SRF02 ultrasonic ranger.
- * The connection between the MCU and the SRF02 is based on the
- * i2c-interface.
+ * @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 "hwtimer.h"
+
+#include "xtimer.h"
#include "srf02.h"
#include "periph/i2c.h"
#define ENABLE_DEBUG (0)
#include "debug.h"
+/**
+ * @brief The datasheet tells us, that ranging takes 70ms
+ */
+#define RANGE_DELAY (70000U)
-int srf02_init(srf02_t *dev, i2c_t i2c, uint8_t addr, i2c_speed_t speed)
+/**
+ * @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)
+/** @} */
+
+int srf02_init(srf02_t *dev, i2c_t i2c, uint8_t addr)
{
- int status;
dev->i2c = i2c;
dev->addr = addr;
+ char rev;
/* Acquire exclusive access to the bus. */
i2c_acquire(dev->i2c);
/* initialize i2c interface */
- status = i2c_init_master(dev->i2c, speed);
+ 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, addr, REG_CMD, &rev);
+ if (rev == 0 || rev == 255) {
+ 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);
- return status;
+ DEBUG("[srf02] initialization successful\n");
+ return 0;
}
uint16_t srf02_get_distance(srf02_t *dev, srf02_mode_t mode)
{
- int status;
- char range_high_byte = 0;
- char range_low_byte = 0;
- uint16_t distance = 0;
+ char res[2];
- /* Acquire exclusive access to the bus. */
+ /* trigger a new measurement by writing the mode to the CMD register */
+ DEBUG("[srf02] trigger new reading\n");
i2c_acquire(dev->i2c);
- /* initialize measure mode*/
- status = i2c_write_reg(dev->i2c, dev->addr, SRF02_COMMAND_REG, mode);
- /* Release the bus for other threads. */
+ i2c_write_reg(dev->i2c, dev->addr, REG_CMD, mode);
i2c_release(dev->i2c);
- if (status < 0) {
- DEBUG("Write the ranging command to the i2c-interface is failed");
- uint16_t distance = UINT16_MAX;
- return distance;
- }
+ /* give the sensor the required time for sampling */
+ xtimer_usleep(RANGE_DELAY);
- hwtimer_wait(70000);
-
- /* Acquire exclusive access to the bus. */
+ /* read the results */
i2c_acquire(dev->i2c);
- status = i2c_read_reg(dev->i2c, dev->addr,
- SRF02_RANGE_HIGH_BYTE, &range_high_byte);
- /* Release the bus for other threads. */
+ 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]);
- if (status < 0) {
- DEBUG("Read the high echo byte from the i2c-interface is failed");
- distance = UINT16_MAX;
- return distance;
- }
-
- /* Acquire exclusive access to the bus. */
- i2c_acquire(dev->i2c);
- status = i2c_read_reg(dev->i2c, dev->addr,
- SRF02_RANGE_LOW_BYTE, &range_low_byte);
- /* Release the bus for other threads. */
- i2c_release(dev->i2c);
-
- if (status < 0) {
- DEBUG("Read the low echo byte from the i2c-interface is failed");
- distance = UINT16_MAX;
- return distance;
- }
-
- distance = (range_high_byte << 8) | (range_low_byte);
-
- return distance;
+ /* compile result - TODO: fix for different host byte order other than LE */
+ return ((((uint16_t)res[0]) << 8) | (res[1] & 0xff));
}
--
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