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RPM_Measure.ino
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RPM_Measure.ino
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/****************************************************************************************************************************
RPM_Measure.ino
For SAM DUE boards
Written by Khoi Hoang
Now even you use all these new 16 ISR-based timers,with their maximum interval practically unlimited (limited only by
unsigned long miliseconds), you just consume only one Hardware timer and avoid conflicting with other cores' tasks.
The accuracy is nearly perfect compared to software timers. The most important feature is they're ISR-based timers
Therefore, their executions are not blocked by bad-behaving functions / tasks.
This important feature is absolutely necessary for mission-critical tasks.
Based on SimpleTimer - A timer library for Arduino.
Author: [email protected]
Copyright (c) 2010 OTTOTECNICA Italy
Based on BlynkTimer.h
Author: Volodymyr Shymanskyy
Built by Khoi Hoang https://github.com/khoih-prog/TimerInterrupt_Generic
Licensed under MIT license
*****************************************************************************************************************************/
/*
Notes:
Special design is necessary to share data between interrupt code and the rest of your program.
Variables usually need to be "volatile" types. Volatile tells the compiler to avoid optimizations that assume
variable can not spontaneously change. Because your function may change variables while your program is using them,
the compiler needs this hint. But volatile alone is often not enough.
When accessing shared variables, usually interrupts must be disabled. Even with volatile,
if the interrupt changes a multi-byte variable between a sequence of instructions, it can be read incorrectly.
If your data is multiple variables, such as an array and a count, usually interrupts need to be disabled
or the entire sequence of your code which accesses the data.
RPM Measuring uses high frequency hardware timer 1Hz == 1ms) to measure the time from of one rotation, in ms
then convert to RPM. One rotation is detected by reading the state of a magnetic REED SW or IR LED Sensor
Asssuming LOW is active.
For example: Max speed is 600RPM => 10 RPS => minimum 100ms a rotation. We'll use 80ms for debouncing
If the time between active state is less than 8ms => consider noise.
RPM = 60000 / (rotation time in ms)
We use interrupt to detect whenever the SW is active, set a flag then use timer to count the time between active state
RPM Measuring uses high frequency hardware timer 1Hz == 1ms) to measure the time from of one rotation, in ms
then convert to RPM. One rotation is detected by reading the state of a magnetic REED SW or IR LED Sensor
Asssuming LOW is active.
For example: Max speed is 600RPM => 10 RPS => minimum 100ms a rotation. We'll use 80ms for debouncing
If the time between active state is less than 8ms => consider noise.
RPM = 60000 / (rotation time in ms)
You can also use interrupt to detect whenever the SW is active, set a flag then use timer to count the time between active state
*/
#if !( defined(ARDUINO_SAM_DUE) || defined(__SAM3X8E__) )
#error This code is designed to run on SAM DUE board / platform! Please check your Tools->Board setting.
#endif
// These define's must be placed at the beginning before #include "TimerInterrupt_Generic.h"
// _TIMERINTERRUPT_LOGLEVEL_ from 0 to 4
// Don't define _TIMERINTERRUPT_LOGLEVEL_ > 0. Only for special ISR debugging only. Can hang the system.
// Don't define TIMER_INTERRUPT_DEBUG > 2. Only for special ISR debugging only. Can hang the system.
#define TIMER_INTERRUPT_DEBUG 0
#define _TIMERINTERRUPT_LOGLEVEL_ 0
#include "TimerInterrupt_Generic.h"
//#ifndef LED_BUILTIN
// #define LED_BUILTIN 13
//#endif
#ifndef LED_BLUE
#define LED_BLUE 2
#endif
#ifndef LED_RED
#define LED_RED 8
#endif
unsigned int SWPin = 7;
#define TIMER0_INTERVAL_MS 1
#define DEBOUNCING_INTERVAL_MS 80
#define LOCAL_DEBUG 1
volatile unsigned long rotationTime = 0;
float RPM = 0.00;
float avgRPM = 0.00;
volatile int debounceCounter;
void TimerHandler()
{
static bool started = false;
if (!started)
{
started = true;
pinMode(SWPin, INPUT_PULLUP);
}
if ( !digitalRead(SWPin) && (debounceCounter >= DEBOUNCING_INTERVAL_MS / TIMER0_INTERVAL_MS ) )
{
//min time between pulses has passed
RPM = (float) ( 60000.0f / ( rotationTime * TIMER0_INTERVAL_MS ) );
avgRPM = ( 2 * avgRPM + RPM) / 3,
#if (TIMER_INTERRUPT_DEBUG > 1)
Serial.print("RPM = "); Serial.print(avgRPM);
Serial.print(", rotationTime ms = "); Serial.println(rotationTime * TIMER1_INTERVAL_MS);
#endif
rotationTime = 0;
debounceCounter = 0;
}
else
{
debounceCounter++;
}
if (rotationTime >= 5000)
{
// If idle, set RPM to 0, don't increase rotationTime
RPM = 0;
#if (TIMER_INTERRUPT_DEBUG > 1)
Serial.print("RPM = "); Serial.print(RPM); Serial.print(", rotationTime = "); Serial.println(rotationTime);
#endif
rotationTime = 0;
}
else
{
rotationTime++;
}
}
uint16_t attachDueInterrupt(double microseconds, timerCallback callback, const char* TimerName)
{
DueTimerInterrupt dueTimerInterrupt = DueTimer.getAvailable();
dueTimerInterrupt.attachInterruptInterval(microseconds, callback);
uint16_t timerNumber = dueTimerInterrupt.getTimerNumber();
Serial.print(TimerName); Serial.print(F(" attached to Timer(")); Serial.print(timerNumber); Serial.println(F(")"));
return timerNumber;
}
void setup()
{
Serial.begin(115200);
while (!Serial);
Serial.print(F("\nStarting RPM_Measure on ")); Serial.println(BOARD_NAME);
Serial.println(SAMDUE_TIMER_INTERRUPT_VERSION);
Serial.println(TIMER_INTERRUPT_GENERIC_VERSION);
Serial.print(F("CPU Frequency = ")); Serial.print(F_CPU / 1000000); Serial.println(F(" MHz"));
Serial.print(F("Timer Frequency = ")); Serial.print(SystemCoreClock / 1000000); Serial.println(F(" MHz"));
// Interval in microsecs
attachDueInterrupt(TIMER0_INTERVAL_MS * 1000, TimerHandler, "ITimer");
Serial.flush();
}
void loop()
{
}