sharp_distance_test.ino

/*
** Copyright (c) 2021, Bradley A. Minch
** 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. 
**
** 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.
*/

uint16_t LOOP_INTERVAL = 20;

uint32_t loop_time;

/*
** Returns a boolean value that indicates whether the current time, t, is later than some prior 
** time, t0, plus a given interval, dt.  The condition accounts for timer overflow / wraparound.
*/
bool it_is_time(uint32_t t, uint32_t t0, uint16_t dt) {
  return ((t >= t0) && (t - t0 >= dt)) ||         // The first disjunct handles the normal case
            ((t < t0) && (t + (~t0) + 1 >= dt));  //   while the second handles the overflow case
}

void setup() {
  Serial.begin(115200);
  
  loop_time = millis();
}

void loop() {
  uint32_t t;
  uint16_t x, y, z, res;

  t = millis();
  if (it_is_time(t, loop_time, LOOP_INTERVAL)) {
    x = analogRead(0);
    y = analogRead(0);
    z = analogRead(0);

    //res = x;
    //res = (x + y + z) / 3;
    res = min(min(x, y), z);
    Serial.println(res);

    loop_time = t;
  }
}