Kronograf

1//
2//    FILE: timeMeasurement.ino
3//  AUTHOR: Rob dot Tillaart  at gmail dot com
4// VERSION: 0.0.1
5// PURPOSE: timeMeasurement Arduino UNO  between 2 interrupts on pin 2 and 3 using timer1
6//     URL: http://forum.arduino.cc/index.php?topic=473669
7//
8//  HISTORY:
9// 0.0.1 - 2017-04-28 initial version
10//
11
12volatile bool inprogress  = false;
13volatile bool dataReady = false;
14volatile uint32_t ticks = 0;
15volatile  uint32_t overflows = 0;
16
17const float ticksPerSecond = 16000000.0;
18const  float sensorDistance = 0.018;
19
20
21
22void setup()
23{
24  Serial.begin(1000000);
25
26  Serial.println(__FILE__);
27  Serial.println();
28
29  pinMode(2, INPUT);
30  pinMode(3, INPUT);
31
32  attachInterrupt(digitalPinToInterrupt(2), startTimer,  RISING);
33  attachInterrupt(digitalPinToInterrupt(3), stopTimer, RISING);
34}
35
36void  loop()
37{
38  if (dataReady && inprogress)
39  {
40    // MATH
41    float  duration = ticks / ticksPerSecond;  // seconds
42    float distance = sensorDistance;          // meter
43    float speed1 = distance / duration;        // meter /  second
44
45    // OUTPUT
46    Serial.print("time: ");
47    Serial.print(ticks  / 16.0, 2);    // 2 decimals
48    Serial.print(" usec ");
49    Serial.print("\	speed:  ");
50    Serial.print(speed1, 3);           // 2 decimals
51    Serial.println("  m/s");
52
53    // PREPARE NEXT MEASUREMENT
54    inprogress = false;
55  }
56}
57
58ISR  (TIMER1_OVF_vect)
59{
60  overflows++;
61}
62
63// note startTimer code itself  takes
64void startTimer()
65{
66  // prevent start interrupt when in progress
67  if (inprogress) return;
68  inprogress = true;
69  dataReady = false;
70
71  TCCR1A = 0;             // 
72  TCCR1B = 0;             // stop
73  TCNT1 =  0;              // reset counter, overflows at 65536
74  overflows = 0;          //  reset overflowCount
75  OCR1A = 1;              // clock pulses per increment TCNT1
76  TIMSK1 = bit(TOIE1);    // set overflow interrupt
77  TCCR1B = bit(CS10);     //  start
78}
79
80void stopTimer()
81{
82  if (dataReady) return;  // prevent  additional stop interrupt
83  dataReady = true;
84
85  TCCR1A = 0;
86  TCCR1B  = 0;
87  TIMSK1 = 0;
88  ticks = overflows * 65536UL + TCNT1;    // calculate  clockticks.
89}
90
91// ---END OF FILE ---