text: /****************************************************************************
   *
   *   Copyright (c) 2012, 2013 PX4 Development Team. All rights reserved.
   *   Author: Lorenz Meier <lm@inf.ethz.ch>
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in
   *    the documentation and/or other materials provided with the
   *    distribution.
   * 3. Neither the name PX4 nor the names of its contributors may be
   *    used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
   * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
   * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   * POSSIBILITY OF SUCH DAMAGE.
   *
   ****************************************************************************/
  
  /**
   * @file i2c.c
   *
   * i2c hacking tool
   */
  
  #include <px4_config.h>
  
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <stdbool.h>
  #include <unistd.h>
  #include <fcntl.h>
  #include <sys/mount.h>
  #include <sys/ioctl.h>
  #include <sys/stat.h>
  
  #include <nuttx/i2c/i2c_master.h>
  
  #include <board_config.h>
  
  #include "systemlib/systemlib.h"
  #include "systemlib/err.h"
  
  #ifndef PX4_I2C_BUS_ONBOARD
  #  error PX4_I2C_BUS_ONBOARD not defined, no device interface
  #endif
  #ifndef PX4_I2C_OBDEV_PX4IO
  #  error PX4_I2C_OBDEV_PX4IO not defined
  #endif
  
  __EXPORT int i2c_main(int argc, char *argv[]);
  
  static int transfer(uint8_t address, uint8_t *send, unsigned send_len, uint8_t *recv, unsigned recv_len);
  
  static struct i2c_master_s *i2c;
  
  int i2c_main(int argc, char *argv[])
  {
  	/* find the right I2C */
  	i2c = px4_i2cbus_initialize(PX4_I2C_BUS_ONBOARD);
  
  	if (i2c == NULL) {
  		errx(1, "failed to locate I2C bus");
  	}
  
  	usleep(100000);
  
  	uint8_t buf[] = { 0, 4};
  	int ret = transfer(PX4_I2C_OBDEV_PX4IO, buf, sizeof(buf), NULL, 0);
  
  	if (ret) {
  		errx(1, "send failed - %d", ret);
  	}
  
  	uint32_t val;
  	ret = transfer(PX4_I2C_OBDEV_PX4IO, NULL, 0, (uint8_t *)&val, sizeof(val));
  
  	if (ret) {
  		errx(1, "recive failed - %d", ret);
  	}
  
  	errx(0, "got 0x%08x", val);
  }
  
  static int
  transfer(uint8_t address, uint8_t *send, unsigned send_len, uint8_t *recv, unsigned recv_len)
  {
  	struct i2c_msg_s msgv[2];
  	unsigned msgs;
  	int ret;
  
  	//	debug("transfer out %p/%u  in %p/%u", send, send_len, recv, recv_len);
  
  	msgs = 0;
  
  	if (send_len > 0) {
  		msgv[msgs].frequency = 400000;
  		msgv[msgs].addr = address;
  		msgv[msgs].flags = 0;
  		msgv[msgs].buffer = send;
  		msgv[msgs].length = send_len;
  		msgs++;
  	}
  
  	if (recv_len > 0) {
  		msgv[msgs].frequency = 400000;
  		msgv[msgs].addr = address;
  		msgv[msgs].flags = I2C_M_READ;
  		msgv[msgs].buffer = recv;
  		msgv[msgs].length = recv_len;
  		msgs++;
  	}
  
  	if (msgs == 0) {
  		return -1;
  	}
  
  	ret = I2C_TRANSFER(i2c, &msgv[0], msgs);
  
  	// reset the I2C bus to unwedge on error
  	if (ret != OK) {
  		up_i2creset(i2c);
  	}
  
  	return ret;
  }
  