osd-contiki/examples/osd/arduino-distance/resources/res-distance.c

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2016-02-23 20:32:53 +01:00
/*
* Copyright (c) 2013, Institute for Pervasive Computing, ETH Zurich
* All rights reserved.
*
* 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 of the Institute 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 INSTITUTE 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 INSTITUTE 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.
*
* This file is part of the Contiki operating system.
*/
/**
* \file
* Moisture resource
* \author
* Harald Pichler <harald@the-develop.net>
*/
#include "contiki.h"
#include <string.h>
#include "rest-engine.h"
#include "Arduino.h"
#include "sketch.h"
#define clockCyclesPerMicrosecond() ( F_CPU / 1000000L )
#define clockCyclesToMicroseconds(a) ( (a) / clockCyclesPerMicrosecond() )
#define microsecondsToClockCycles(a) ( (a) * clockCyclesPerMicrosecond() )
unsigned long pulseIn(uint8_t pin, uint8_t state, unsigned long timeout)
{
// cache the port and bit of the pin in order to speed up the
// pulse width measuring loop and achieve finer resolution. calling
// digitalRead() instead yields much coarser resolution.
uint8_t bit = digitalPinToBitMask(pin);
uint8_t port = digitalPinToPort(pin);
uint8_t stateMask = (state ? bit : 0);
unsigned long width = 0; // keep initialization out of time critical area
// convert the timeout from microseconds to a number of times through
// the initial loop; it takes 16 clock cycles per iteration.
unsigned long numloops = 0;
unsigned long maxloops = microsecondsToClockCycles(timeout) / 16;
// wait for any previous pulse to end
while ((*portInputRegister(port) & bit) == stateMask)
if (numloops++ == maxloops)
return 0;
// wait for the pulse to start
while ((*portInputRegister(port) & bit) != stateMask)
if (numloops++ == maxloops)
return 0;
// wait for the pulse to stop
while ((*portInputRegister(port) & bit) == stateMask)
width++;
// convert the reading to microseconds. The loop has been determined
// to be 10 clock cycles long and have about 16 clocks between the edge
// and the start of the loop. There will be some error introduced by
// the interrupt handlers.
return clockCyclesToMicroseconds(width * 10 + 16);
}
static void res_get_handler(void *request, void *response, uint8_t *buffer, uint16_t preferred_size, int32_t *offset);
/* A simple getter example. Returns the reading from the sensor with a simple etag */
RESOURCE(res_distance,
"title=\"Distance status\";rt=\"Distance\"",
res_get_handler,
NULL,
NULL,
NULL);
static void
res_get_handler(void *request, void *response, uint8_t *buffer, uint16_t preferred_size, int32_t *offset)
{
unsigned int accept = -1;
REST.get_header_accept(request, &accept);
long duration, distance;
digitalWrite(TRIG_PIN, LOW);
delayMicroseconds(2);
digitalWrite(TRIG_PIN, HIGH);
delayMicroseconds(20);
digitalWrite(TRIG_PIN, LOW);
duration = pulseIn(ECHO_PIN, HIGH, 500000);
// found this computation in some arduino examples
//distance = (duration/2) / 29.1;
// to get millimeters (duration -20) / 3.18 is a good approach
distance = (duration-20)/3.18;
if(accept == -1 || accept == REST.type.TEXT_PLAIN) {
REST.set_header_content_type(response, REST.type.TEXT_PLAIN);
snprintf((char *)buffer, REST_MAX_CHUNK_SIZE, "%ld", distance);
REST.set_response_payload(response, buffer, strlen((char *)buffer));
} else if(accept == REST.type.APPLICATION_JSON) {
REST.set_header_content_type(response, REST.type.APPLICATION_JSON);
snprintf((char *)buffer, REST_MAX_CHUNK_SIZE, "{'distance':%ld}", distance);
REST.set_response_payload(response, buffer, strlen((char *)buffer));
} else {
REST.set_response_status(response, REST.status.NOT_ACCEPTABLE);
const char *msg = "Supporting content-types text/plain and application/json";
REST.set_response_payload(response, msg, strlen(msg));
}
}