text: /****************************************************************************
   *
   * Copyright 2017 Samsung Electronics All Rights Reserved.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied. See the License for the specific
   * language governing permissions and limitations under the License.
   *
   ****************************************************************************/
  /****************************************************************************
   * examples/examples/sensorbd/examples/gpio_loopback.c
   *
   *   Copyright (C) 2012 Gregory Nutt. All rights reserved.
   *   Author: Gregory Nutt <gnutt@nuttx.org>
   *
   * 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 NuttX 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.
   *
   ****************************************************************************/
  
  #include <stdlib.h>
  #include <fcntl.h>
  #include <tinyara/gpio.h>
  
  #define XGPIO1 30
  #define XGPIO2 31
  #define XGPIO3 32
  #define XGPIO8 37
  #define XGPIO9 38
  #define XGPIO11 40
  
  static int gpio_read(int port)
  {
  	char buf[4];
  	char devpath[16];
  	snprintf(devpath, 16, "/dev/gpio%d", port);
  	int fd = open(devpath, O_RDWR);
  	if (fd < 0) {
  		printf("fd open fail\n");
  		return -1;
  	}
  
  	if (read(fd, buf, sizeof(buf)) < 0) {
  		printf("read error\n");
  		return -1;
  	}
  	close(fd);
  
  	return buf[0] == '1';
  }
  
  static void gpio_write(int port, int value)
  {
  	char buf[4];
  	char devpath[16];
  	snprintf(devpath, 16, "/dev/gpio%d", port);
  	int fd = open(devpath, O_RDWR);
  	if (fd < 0) {
  		printf("fd open fail\n");
  		return;
  	}
  
  	ioctl(fd, GPIOIOC_SET_DIRECTION, GPIO_DIRECTION_OUT);
  	if (write(fd, buf, snprintf(buf, sizeof(buf), "%d", !!value)) < 0) {
  		printf("write error\n");
  		return;
  	}
  	close(fd);
  }
  
  void gpioloopback_main(int argc, char *argv[])
  {
  	int tc;
  	for (tc = 0; tc < 3; tc++) {
  		int nA = 0, nB = 0;
  		switch (tc) {
  		case 0:
  			nA = XGPIO9;
  			nB = XGPIO11;
  			break;
  		case 1:
  			nA = XGPIO8;
  			nB = XGPIO2;
  			break;
  		case 2:
  			nA = XGPIO1;
  			nB = XGPIO3;
  			break;
  		}
  
  		int readA, readB;
  		readA = gpio_read(nA);
  
  		if (readA == 0) {
  			gpio_write(nA, 1);
  
  			readA = gpio_read(nA);
  			readB = gpio_read(nB);
  
  			if (readA != readB) {
  				printf("gpio%d and gpio%d is not connect!\n", nA, nB);
  			} else {
  				printf("gpio%d and gpio%d is connect!\n", nA, nB);
  			}
  		} else {
  			gpio_write(nA, 0);
  
  			readA = gpio_read(nA);
  			readB = gpio_read(nB);
  
  			if (readA != readB) {
  				printf("gpio%d and gpio%d is not connect!\n", nA, nB);
  			} else {
  				printf("gpio%d and gpio%d is connect!\n", nA, nB);
  			}
  		}
  
  		gpio_write(nA, 0);
  	}
  }
  