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RepeatedAttachInterrupt_uS.ino
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/****************************************************************************************************************************
RepeatedAttachInterrupt_uS.ino
For SAMD boards
Written by Khoi Hoang
Built by Khoi Hoang https://github.com/khoih-prog/SAMD_TimerInterrupt
Licensed under MIT license
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 SAMD 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.
*****************************************************************************************************************************/
/*
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.
Based on the sketch of (https://github.com/thiagothimotti) posted in (https://github.com/khoih-prog/SAMD_TimerInterrupt/issues/3)
to report the issue: "Bug when going from a >20000us period to a <20000us period. The timer period become 4 times greater. #3"
*/
#if !( defined(ARDUINO_SAMD_ZERO) || defined(ARDUINO_SAMD_MKR1000) || defined(ARDUINO_SAMD_MKRWIFI1010) \
|| defined(ARDUINO_SAMD_NANO_33_IOT) || defined(ARDUINO_SAMD_MKRFox1200) || defined(ARDUINO_SAMD_MKRWAN1300) || defined(ARDUINO_SAMD_MKRWAN1310) \
|| defined(ARDUINO_SAMD_MKRGSM1400) || defined(ARDUINO_SAMD_MKRNB1500) || defined(ARDUINO_SAMD_MKRVIDOR4000) \
|| defined(ARDUINO_SAMD_CIRCUITPLAYGROUND_EXPRESS) || defined(__SAMD51__) || defined(__SAMD51J20A__) \
|| defined(__SAMD51J19A__) || defined(__SAMD51G19A__) || defined(__SAMD51P19A__) \
|| defined(__SAMD21E15A__) || defined(__SAMD21E16A__) || defined(__SAMD21E17A__) || defined(__SAMD21E18A__) \
|| defined(__SAMD21G15A__) || defined(__SAMD21G16A__) || defined(__SAMD21G17A__) || defined(__SAMD21G18A__) \
|| defined(__SAMD21J15A__) || defined(__SAMD21J16A__) || defined(__SAMD21J17A__) || defined(__SAMD21J18A__) )
#error This code is designed to run on SAMD21/SAMD51 platform! Please check your Tools->Board setting.
#endif
/////////////////////////////////////////////////////////////////
// These define's must be placed at the beginning before #include "SAMDTimerInterrupt.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
// Select only one to be true for SAMD21. Must must be placed at the beginning before #include "SAMDTimerInterrupt.h"
#define USING_TIMER_TC3 true // Only TC3 can be used for SAMD51
#define USING_TIMER_TC4 false // Not to use with Servo library
#define USING_TIMER_TC5 false
#define USING_TIMER_TCC false
#define USING_TIMER_TCC1 false
#define USING_TIMER_TCC2 false // Don't use this, can crash on some boards
// Uncomment To test if conflict with Servo library
//#include "Servo.h"
/////////////////////////////////////////////////////////////////
// To be included only in main(), .ino with setup() to avoid `Multiple Definitions` Linker Error
#include "SAMDTimerInterrupt.h"
#if USING_TIMER_TC3
#define SELECTED_TIMER TIMER_TC3
#elif USING_TIMER_TC4
#define SELECTED_TIMER TIMER_TC4
#elif USING_TIMER_TC5
#define SELECTED_TIMER TIMER_TC5
#elif USING_TIMER_TCC
#define SELECTED_TIMER TIMER_TCC
#elif USING_TIMER_TCC1
#define SELECTED_TIMER TIMER_TCC1
#elif USING_TIMER_TCC2
#define SELECTED_TIMER TIMER_TCC
#else
#error You have to select 1 Timer
#endif
// Init selected SAMD timer
SAMDTimer ITimer(SELECTED_TIMER);
volatile uint32_t myClockTimer = 0, lastMicros = 0;
void clock(void)
{
myClockTimer = micros() - lastMicros; //2us come from here
lastMicros = micros();
}
void setup()
{
Serial.begin(115200);
while (!Serial && millis() < 5000);
delay(100);
Serial.print(F("\nStarting RepeatedAttachInterrupt_uS on ")); Serial.println(BOARD_NAME);
Serial.println(SAMD_TIMER_INTERRUPT_VERSION);
Serial.print(F("CPU Frequency = ")); Serial.print(F_CPU / 1000000); Serial.println(F(" MHz"));
}
void loop()
{
ITimer.attachInterruptInterval(19995, clock);
delay(5000);
Serial.print(F("myClockTimer (19995) = ")); Serial.println(myClockTimer);
ITimer.attachInterruptInterval(19995, clock);
delay(5000);
Serial.print(F("myClockTimer (19995) = ")); Serial.println(myClockTimer);
ITimer.attachInterruptInterval(19995, clock);
delay(5000);
Serial.print(F("myClockTimer (19995) = ")); Serial.println(myClockTimer);
ITimer.attachInterruptInterval(19000, clock);
delay(5000);
Serial.print(F("myClockTimer (19000) = ")); Serial.println(myClockTimer);
ITimer.attachInterruptInterval(20005, clock);
delay(5000);
Serial.print(F("myClockTimer (20005) = ")); Serial.println(myClockTimer);
ITimer.attachInterruptInterval(30000, clock);
delay(5000);
Serial.print(F("myClockTimer (30000) = ")); Serial.println(myClockTimer);
ITimer.attachInterruptInterval(19995, clock);
delay(5000);
Serial.print(F("myClockTimer (19995) = ")); Serial.println(myClockTimer);
ITimer.attachInterruptInterval(30000, clock);
delay(5000);
Serial.print(F("myClockTimer (30000) = ")); Serial.println(myClockTimer);
}