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This library enables you to use Interrupt from Hardware Timers on an ESP8266-based board. It now supports 16 ISR-based timers, while consuming only 1 hardware Timer. Timers' interval is very long (ulong millisecs). The most important feature is they're ISR-based timers. Therefore, their executions are not blocked by bad-behaving functions or tas…

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ESP8266TimerInterrupt Library

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Table of Contents

Important Change from v1.6.0

Please have a look at HOWTO Fix Multiple Definitions Linker Error

Why do we need this ESP8266TimerInterrupt library

Features

This library enables you to use Interrupt from Hardware Timers on an ESP8266-based board.

As Hardware Timers are rare, and very precious assets of any board, this library now enables you to use up to 16 ISR-based Timers, while consuming only 1 Hardware Timer. Timers' interval is very long (ulong millisecs).

Now with these new 16 ISR-based timers, the maximum interval is practically unlimited (limited only by unsigned long milliseconds) while 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.

The ISR_Timer_Complex example will demonstrate the nearly perfect accuracy compared to software timers by printing the actual elapsed millisecs of each type of timers.

Being ISR-based timers, their executions are not blocked by bad-behaving functions / tasks, such as connecting to WiFi, Internet and Blynk services. You can also have many (up to 16) timers to use.

This non-being-blocked important feature is absolutely necessary for mission-critical tasks.

You'll see blynkTimer Software is blocked while system is connecting to WiFi / Internet / Blynk, as well as by blocking task in loop(), using delay() function as an example. The elapsed time then is very unaccurate

Why using ISR-based Hardware Timer Interrupt is better

Imagine you have a system with a mission-critical function, measuring water level and control the sump pump or doing something much more important. You normally use a software timer to poll, or even place the function in loop(). But what if another function is blocking the loop() or setup().

So your function might not be executed, and the result would be disastrous.

You'd prefer to have your function called, no matter what happening with other functions (busy loop, bug, etc.).

The correct choice is to use a Hardware Timer with Interrupt to call your function.

These hardware timers, using interrupt, still work even if other functions are blocking. Moreover, they are much more precise (certainly depending on clock frequency accuracy) than other software timers using millis() or micros(). That's necessary if you need to measure some data requiring better accuracy.

Functions using normal software timers, relying on loop() and calling millis(), won't work if the loop() or setup() is blocked by certain operation. For example, certain function is blocking while it's connecting to WiFi or some services.

The catch is your function is now part of an ISR (Interrupt Service Routine), and must be lean / mean, and follow certain rules. More to read on:

HOWTO Attach Interrupt

Currently supported Boards

  1. ESP8266-based boards

Important Notes about ISR

  1. Inside the attached function, delay() won’t work and the value returned by millis() will not increment. Serial data received while in the function may be lost. You should declare as volatile any variables that you modify within the attached function.

  2. Typically global variables are used to pass data between an ISR and the main program. To make sure variables shared between an ISR and the main program are updated correctly, declare them as volatile.

Prerequisites

  1. Arduino IDE 1.8.19+ for Arduino. GitHub release
  2. ESP8266 Core 3.0.2+ for ESP8266-based boards. Latest release. To use ESP8266 core 2.7.1+ for LittleFS.
  3. SimpleTimer library to use with some examples.

Installation

Use Arduino Library Manager

The best and easiest way is to use Arduino Library Manager. Search for ESP8266TimerInterrupt, then select / install the latest version. You can also use this link arduino-library-badge for more detailed instructions.

Manual Install

Another way to install is to:

  1. Navigate to ESP8266TimerInterrupt page.
  2. Download the latest release ESP8266TimerInterrupt-master.zip.
  3. Extract the zip file to ESP8266TimerInterrupt-master directory
  4. Copy whole ESP8266TimerInterrupt-master folder to Arduino libraries' directory such as ~/Arduino/libraries/.

VS Code & PlatformIO

  1. Install VS Code
  2. Install PlatformIO
  3. Install ESP8266TimerInterrupt library by using Library Manager. Search for ESP8266TimerInterrupt in Platform.io Author's Libraries
  4. Use included platformio.ini file from examples to ensure that all dependent libraries will installed automatically. Please visit documentation for the other options and examples at Project Configuration File

HOWTO Fix Multiple Definitions Linker Error

The current library implementation, using xyz-Impl.h instead of standard xyz.cpp, possibly creates certain Multiple Definitions Linker error in certain use cases.

You can use

#include "ESP8266TimerInterrupt.h" //https://github.com/khoih-prog/ESP8266TimerInterrupt #include "ESP8266_ISR_Timer.hpp" //https://github.com/khoih-prog/ESP8266TimerInterrupt

in many files. But be sure to use the following #include <ESP8266_ISR_Timer.h> in just 1 .h, .cpp or .ino file, which must not be included in any other file, to avoid Multiple Definitions Linker Error

// To be included only in main(), .ino with setup() to avoid `Multiple Definitions` Linker Error #include "ESP8266_ISR_Timer.h" //https://github.com/khoih-prog/ESP8266TimerInterrupt

Check the new multiFileProject example for a HOWTO demo.

Have a look at the discussion in Different behaviour using the src_cpp or src_h lib #80

HOWTO Use PWM analogWrite() with ESP8266 running Timer1 Interrupt

Please have a look at ESP8266TimerInterrupt Issue 8: ESP8266Timer and PWM --> wdt reset to have more detailed description and solution of the issue.

1. ESP8266 has only 2 hardware timers, named Timer0 and Timer1

2. ESP8266 hardware timers' functions

  • Timer0 has been used for WiFi and it's not advisable to use while using WiFi (if not using WiFi, why select ESP8266 ??)
  • Timer1 is used by this ESP8266TimerInterrupt Library

3. How to use PWM analogWrite() functions while using this library

  1. If possible, use software timer instead of ESP8266TimerInterrupt Hardware Timer1
  2. If using ESP8266TimerInterrupt Hardware Timer1 is a must, you can either

More useful Information

The ESP8266 timers are badly designed, using only 23-bit counter along with maximum 256 prescaler. They're only better than UNO / Mega. The ESP8266 has two hardware timers, but timer0 has been used for WiFi and it's not advisable to use. Only timer1 is available. The timer1's 23-bit counter terribly can count only up to 8,388,607. So the timer1 maximum interval is very short. Using 256 prescaler, maximum timer1 interval is only 26.843542 seconds !!!

The timer1 counters can be configured to support automatic reload.

Now with these new 16 ISR-based timers, the maximum interval is practically unlimited (limited only by unsigned long milliseconds).

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.

The ISR_Timer_Complex example will demonstrate the nearly perfect accuracy compared to software timers by printing the actual elapsed millisecs of each type of timers.

Being ISR-based timers, their executions are not blocked by bad-behaving functions / tasks, such as connecting to WiFi, Internet and Blynk services. You can also have many (up to 16) timers to use. This non-being-blocked important feature is absolutely necessary for mission-critical tasks.

You'll see blynkTimer Software is blocked while system is connecting to WiFi / Internet / Blynk, as well as by blocking task in loop(), using delay() function as an example. The elapsed time then is very unaccurate

Usage

The ESP8266 timers are badly designed, using only 23-bit counter along with maximum 256 prescaler. They're only better than UNO / Mega.

The ESP8266 has two hardware timers, but Timer0 has been used for WiFi and it's not advisable to use. Only Timer1 is available.

The Timer1's 23-bit counter can terribly count only up to 8,388,607. So the timer1 maximum interval is very short. Using 256 prescaler, maximum Timer1 interval is only 26.843542 seconds !!!

1. Using only Hardware Timer directly

1.1 Init Hardware Timer

// Select a Timer Clock #define USING_TIM_DIV1 false // for shortest and most accurate timer #define USING_TIM_DIV16 false // for medium time and medium accurate timer #define USING_TIM_DIV256 true // for longest timer but least accurate. Default // Init ESP8266 only and only Timer 1 ESP8266Timer ITimer;

1.2 Set Hardware Timer Interval and attach Timer Interrupt Handler function

Use one of these functions with interval in unsigned long milliseconds

// interval (in microseconds) bool setInterval(unsigned long interval, timer_callback callback) // interval (in microseconds) bool attachInterruptInterval(unsigned long interval, timer_callback callback)

as follows

void IRAM_ATTR TimerHandler() { // Doing something here inside ISR } #define TIMER_INTERVAL_MS 1000 void setup() { .... // Interval in microsecs if (ITimer.attachInterruptInterval(TIMER_INTERVAL_MS * 1000, TimerHandler)) { lastMillis = millis(); Serial.print(F("Starting ITimer OK, millis() = ")); Serial.println(lastMillis); } else Serial.println(F("Can't set ITimer correctly. Select another freq. or interval")); }

1.3 Set Hardware Timer Frequency and attach Timer Interrupt Handler function

Use one of these functions with frequency in float Hz

// frequency (in hertz) bool setFrequency(float frequency, timer_callback callback) // frequency (in hertz) bool attachInterrupt(float frequency, timer_callback callback)

as follows

void TimerHandler() { // Doing something here inside ISR } #define TIMER_FREQ_HZ 5555.555 void setup() { .... // Frequency in float Hz if (ITimer.attachInterrupt(TIMER_FREQ_HZ, TimerHandler)) Serial.println("Starting ITimer OK, millis() = " + String(millis())); else Serial.println("Can't set ITimer. Select another freq. or timer"); }

2. Using 16 ISR_based Timers from 1 Hardware Timer

2.1 Important Note

The 16 ISR_based Timers, designed for long timer intervals, only support using unsigned long millisec intervals. If you have to use much higher frequency or sub-millisecond interval, you have to use the Hardware Timers directly as in 1.3 Set Hardware Timer Frequency and attach Timer Interrupt Handler function

2.2 Init Hardware Timer and ISR-based Timer

// Select a Timer Clock #define USING_TIM_DIV1 false // for shortest and most accurate timer #define USING_TIM_DIV16 false // for medium time and medium accurate timer #define USING_TIM_DIV256 true // for longest timer but least accurate. Default #include "ESP8266TimerInterrupt.h" #include "ESP8266_ISR_Timer.h" // Init ESP8266 timer 1 ESP8266Timer ITimer; // Init ESP8266_ISR_Timer ESP8266_ISR_Timer ISR_Timer;

2.3 Set Hardware Timer Interval and attach Timer Interrupt Handler functions

void IRAM_ATTR TimerHandler() { ISR_timer.run(); } #define HW_TIMER_INTERVAL_MS 50L #define TIMER_INTERVAL_2S 2000L #define TIMER_INTERVAL_5S 5000L #define TIMER_INTERVAL_11S 11000L #define TIMER_INTERVAL_101S 101000L // In AVR, avoid doing something fancy in ISR, for example complex Serial.print with String() argument // The pure simple Serial.prints here are just for demonstration and testing. Must be eliminate in working environment // Or you can get this run-time error / crash void doingSomething2s() { // Doing something here inside ISR every 2 seconds } void doingSomething5s() { // Doing something here inside ISR every 5 seconds } void doingSomething11s() { // Doing something here inside ISR every 11 seconds } void doingSomething101s() { // Doing something here inside ISR every 101 seconds } void setup() { .... // Interval in microsecs if (ITimer.attachInterruptInterval(HW_TIMER_INTERVAL_MS * 1000, TimerHandler)) { startMillis = millis(); Serial.print(F("Starting ITimer OK, millis() = ")); Serial.println(startMillis); } else Serial.println(F("Can't set ITimer. Select another freq. or timer")); // Just to demonstrate, don't use too many ISR Timers if not absolutely necessary // You can use up to 16 timer for each ISR_Timer ISR_timer.setInterval(TIMER_INTERVAL_2S, doingSomething2s); ISR_timer.setInterval(TIMER_INTERVAL_5S, doingSomething5s); ISR_timer.setInterval(TIMER_INTERVAL_11S, doingSomething11s); ISR_timer.setInterval(TIMER_INTERVAL_101S, doingSomething101s); }

2.4 Set One-Shot Hardware Timer Interval

ESP8266TimerInterrupt/examples/ISR_16_Timers_Array_OneShot/ISR_16_Timers_Array_OneShot.ino

Lines 414 to 421 in f497e73

// Just to demonstrate, don't use too many ISR Timers if not absolutely necessary
// You can use up to 16 timer for each SAMD_ISR_Timer
for (uint16_t i = 0; i < NUMBER_ISR_TIMERS; i++)
{
//ISR_Timer.setInterval(TimerInterval[i], irqCallbackFunc[i]);
// Use this for one shot ISR TImer
ISR_Timer.setTimeout(TimerInterval[i], irqCallbackFunc[i]);
}

Examples:

  1. Argument_None
  2. ISR_RPM_Measure
  3. RPM_Measure
  4. SwitchDebounce
  5. TimerInterruptTest
  6. Change_Interval.
  7. ISR_16_Timers_Array
  8. ISR_16_Timers_Array_Complex
  9. ISR_16_Timers_Array_OneShot New
  10. multiFileProject New

Example Change_Interval

ESP8266TimerInterrupt/examples/Change_Interval/Change_Interval.ino

Lines 32 to 130 in f497e73

#if !defined(ESP8266)
#error This code is designed to run on ESP8266 and ESP8266-based boards! Please check your Tools->Board setting.
#endif
// These define's must be placed at the beginning before #include "ESP8266TimerInterrupt.h"
// _TIMERINTERRUPT_LOGLEVEL_ from 0 to 4
// Don't define _TIMERINTERRUPT_LOGLEVEL_ > 0. Only for special ISR debugging only. Can hang the system.
#define TIMER_INTERRUPT_DEBUG 0
#define _TIMERINTERRUPT_LOGLEVEL_ 0
// Select a Timer Clock
#define USING_TIM_DIV1 false // for shortest and most accurate timer
#define USING_TIM_DIV16 false // for medium time and medium accurate timer
#define USING_TIM_DIV256 true // for longest timer but least accurate. Default
#include "ESP8266TimerInterrupt.h"
#ifndef LED_BUILTIN
#define LED_BUILTIN D4 // Pin D4 mapped to pin GPIO2/TXD1 of ESP8266, NodeMCU and WeMoS, control on-board LED
#endif
#define TIMER_INTERVAL_MS 500 //1000
volatile uint32_t TimerCount = 0;
// Init ESP8266 timer 1
ESP8266Timer ITimer;
void printResult(uint32_t currTime)
{
Serial.print(F("Time = ")); Serial.print(currTime);
Serial.print(F(", TimerCount = ")); Serial.println(TimerCount);
}
void TimerHandler()
{
static bool toggle = false;
// Flag for checking to be sure ISR is working as Serial.print is not OK here in ISR
TimerCount++;
//timer interrupt toggles pin LED_BUILTIN
digitalWrite(LED_BUILTIN, toggle);
toggle = !toggle;
}
void setup()
{
pinMode(LED_BUILTIN, OUTPUT);
Serial.begin(115200);
while (!Serial);
delay(300);
Serial.print(F("\nStarting Change_Interval on ")); Serial.println(ARDUINO_BOARD);
Serial.println(ESP8266_TIMER_INTERRUPT_VERSION);
Serial.print(F("CPU Frequency = ")); Serial.print(F_CPU / 1000000); Serial.println(F(" MHz"));
// Interval in microsecs
if (ITimer.attachInterruptInterval(TIMER_INTERVAL_MS * 1000, TimerHandler))
{
Serial.print(F("Starting ITimer OK, millis() = ")); Serial.println(millis());
}
else
Serial.println(F("Can't set ITimer. Select another freq. or timer"));
}
#define CHECK_INTERVAL_MS 10000L
#define CHANGE_INTERVAL_MS 20000L
void loop()
{
static uint32_t lastTime = 0;
static uint32_t lastChangeTime = 0;
static uint32_t currTime;
static uint32_t multFactor = 0;
currTime = millis();
if (currTime - lastTime > CHECK_INTERVAL_MS)
{
printResult(currTime);
lastTime = currTime;
if (currTime - lastChangeTime > CHANGE_INTERVAL_MS)
{
//setInterval(unsigned long interval, timerCallback callback)
multFactor = (multFactor + 1) % 2;
ITimer.setInterval(TIMER_INTERVAL_MS * 1000 * (multFactor + 1), TimerHandler);
Serial.print(F("Changing Interval, Timer = ")); Serial.println(TIMER_INTERVAL_MS * (multFactor + 1));
lastChangeTime = currTime;
}
}
}

Debug Terminal Output Samples

1. TimerInterruptTest on ESP8266_NODEMCU_ESP12E

The following is the sample terminal output when running example TimerInterruptTest on ESP8266_NODEMCU_ESP12E to demonstrate the accuracy of Hardware Timers.

Starting TimerInterruptTest on ESP8266_NODEMCU_ESP12E ESP8266TimerInterrupt v1.6.0 CPU Frequency = 160 MHz ESP8266TimerInterrupt: _fre = 312500.00, _count = 312500 Starting ITimer OK, millis() = 262 Delta ms = 1000 Delta ms = 1000 Delta ms = 1000 Delta ms = 1000 Delta ms = 1000 Delta ms = 1000 Delta ms = 1000 Delta ms = 1000 Delta ms = 1000 Delta ms = 1000 Delta ms = 1000 Delta ms = 1000 Delta ms = 1000 Delta ms = 1000 Delta ms = 1000 Delta ms = 1000 Delta ms = 1000

2. Change_Interval on ESP8266_NODEMCU_ESP12E

The following is the sample terminal output when running example Change_Interval on ESP8266_NODEMCU_ESP12E to demonstrate how to change Timer Interval on-the-fly

Starting Change_Interval on ESP8266_NODEMCU_ESP12E ESP8266TimerInterrupt v1.6.0 CPU Frequency = 160 MHz Starting ITimer OK, millis() = 162 Time = 10001, TimerCount = 19 Time = 20002, TimerCount = 39 Changing Interval, Timer = 1000 Time = 30003, TimerCount = 49 Time = 40004, TimerCount = 59 Changing Interval, Timer = 500 Time = 50005, TimerCount = 79 Time = 60006, TimerCount = 99 Changing Interval, Timer = 1000 Time = 70007, TimerCount = 109 Time = 80008, TimerCount = 119 Changing Interval, Timer = 500 Time = 90009, TimerCount = 139 Time = 100010, TimerCount = 159 Changing Interval, Timer = 1000 Time = 110011, TimerCount = 169 Time = 120012, TimerCount = 179 Changing Interval, Timer = 500 Time = 130013, TimerCount = 199 Time = 140014, TimerCount = 219 Changing Interval, Timer = 1000 Time = 150015, TimerCount = 229 Time = 160016, TimerCount = 239 Changing Interval, Timer = 500 Time = 170017, TimerCount = 259 Time = 180018, TimerCount = 279

3. ISR_16_Timers_Array on ESP8266_NODEMCU_ESP12E

The following is the sample terminal output when running example ISR_16_Timers_Array on ESP8266_NODEMCU_ESP12E to demonstrate of ISR Hardware Timer, especially when system is very busy or blocked. The 16 independent ISR timers are programmed to be activated repetitively after certain intervals, is activated exactly after that programmed interval !!!

Starting ISR_16_Timers_Array on ESP8266_NODEMCU_ESP12E ESP8266TimerInterrupt v1.6.0 CPU Frequency = 160 MHz Starting ITimer OK, millis() = 175 1s: Delta ms = 1003, ms = 1178 1s: Delta ms = 999, ms = 2177 2s: Delta ms = 2002, ms = 2177 1s: Delta ms = 1000, ms = 3177 3s: Delta ms = 3002, ms = 3177 1s: Delta ms = 1000, ms = 4177 2s: Delta ms = 2000, ms = 4177 4s: Delta ms = 4002, ms = 4177 1s: Delta ms = 1000, ms = 5177 5s: Delta ms = 5002, ms = 5177 1s: Delta ms = 1000, ms = 6177 2s: Delta ms = 2001, ms = 6178 3s: Delta ms = 3001, ms = 6178 6s: Delta ms = 6003, ms = 6178 1s: Delta ms = 1000, ms = 7177 7s: Delta ms = 7002, ms = 7177 1s: Delta ms = 1000, ms = 8177 2s: Delta ms = 1999, ms = 8177 4s: Delta ms = 4000, ms = 8177 8s: Delta ms = 8002, ms = 8177 1s: Delta ms = 1000, ms = 9177 3s: Delta ms = 2999, ms = 9177 9s: Delta ms = 9002, ms = 9177 simpleTimerDoingSomething2s: Delta programmed ms = 2000, actual = 10002 1s: Delta ms = 1000, ms = 10177 2s: Delta ms = 2000, ms = 10177 5s: Delta ms = 5001, ms = 10178 10s: Delta ms = 10006, ms = 10181 1s: Delta ms = 1000, ms = 11177 11s: Delta ms = 11003, ms = 11178 1s: Delta ms = 1000, ms = 12177 2s: Delta ms = 2000, ms = 12177 3s: Delta ms = 3000, ms = 12177 4s: Delta ms = 4000, ms = 12177 6s: Delta ms = 5999, ms = 12177 12s: Delta ms = 12005, ms = 12180 1s: Delta ms = 1000, ms = 13177 13s: Delta ms = 13002, ms = 13177 1s: Delta ms = 1000, ms = 14177 2s: Delta ms = 2000, ms = 14177 7s: Delta ms = 7000, ms = 14177 14s: Delta ms = 14002, ms = 14177 1s: Delta ms = 1000, ms = 15177 3s: Delta ms = 3000, ms = 15177 5s: Delta ms = 4999, ms = 15177 15s: Delta ms = 15002, ms = 15177 1s: Delta ms = 1000, ms = 16177 2s: Delta ms = 2000, ms = 16177 4s: Delta ms = 4001, ms = 16178 8s: Delta ms = 8001, ms = 16178 16s: Delta ms = 16003, ms = 16178 1s: Delta ms = 1000, ms = 17177 1s: Delta ms = 1000, ms = 18177 2s: Delta ms = 2000, ms = 18177 3s: Delta ms = 3000, ms = 18177 6s: Delta ms = 6000, ms = 18177 9s: Delta ms = 9001, ms = 18178 1s: Delta ms = 1000, ms = 19177 simpleTimerDoingSomething2s: Delta programmed ms = 2000, actual = 10000

4. ISR_16_Timers_Array_Complex on ESP8266_NODEMCU_ESP12E

The following is the sample terminal output when running example ISR_16_Timers_Array_Complex on ESP8266_NODEMCU_ESP12E to demonstrate the ISR Hardware Timer, especially when system is very busy or blocked. The 16 independent ISR timers are programmed to be activated repetitively after certain intervals, is activated exactly after that programmed interval !!!

Starting ISR_16_Timers_Array_Complex on ESP8266_NODEMCU_ESP12E ESP8266TimerInterrupt v1.6.0 CPU Frequency = 160 MHz Starting ITimer OK, millis() = 177 SimpleTimer : 2, ms : 10179, Dms : 10000 Timer : 0, programmed : 5000, actual : 5008 Timer : 1, programmed : 10000, actual : 0 Timer : 2, programmed : 15000, actual : 0 Timer : 3, programmed : 20000, actual : 0 Timer : 4, programmed : 25000, actual : 0 Timer : 5, programmed : 30000, actual : 0 Timer : 6, programmed : 35000, actual : 0 Timer : 7, programmed : 40000, actual : 0 Timer : 8, programmed : 45000, actual : 0 Timer : 9, programmed : 50000, actual : 0 Timer : 10, programmed : 55000, actual : 0 Timer : 11, programmed : 60000, actual : 0 Timer : 12, programmed : 65000, actual : 0 Timer : 13, programmed : 70000, actual : 0 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 SimpleTimer : 2, ms : 20232, Dms : 10053 Timer : 0, programmed : 5000, actual : 5000 Timer : 1, programmed : 10000, actual : 10000 Timer : 2, programmed : 15000, actual : 15008 Timer : 3, programmed : 20000, actual : 20008 Timer : 4, programmed : 25000, actual : 0 Timer : 5, programmed : 30000, actual : 0 Timer : 6, programmed : 35000, actual : 0 Timer : 7, programmed : 40000, actual : 0 Timer : 8, programmed : 45000, actual : 0 Timer : 9, programmed : 50000, actual : 0 Timer : 10, programmed : 55000, actual : 0 Timer : 11, programmed : 60000, actual : 0 Timer : 12, programmed : 65000, actual : 0 Timer : 13, programmed : 70000, actual : 0 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 SimpleTimer : 2, ms : 30286, Dms : 10054 Timer : 0, programmed : 5000, actual : 5000 Timer : 1, programmed : 10000, actual : 10000 Timer : 2, programmed : 15000, actual : 15000 Timer : 3, programmed : 20000, actual : 20008 Timer : 4, programmed : 25000, actual : 25008 Timer : 5, programmed : 30000, actual : 30008 Timer : 6, programmed : 35000, actual : 0 Timer : 7, programmed : 40000, actual : 0 Timer : 8, programmed : 45000, actual : 0 Timer : 9, programmed : 50000, actual : 0 Timer : 10, programmed : 55000, actual : 0 Timer : 11, programmed : 60000, actual : 0 Timer : 12, programmed : 65000, actual : 0 Timer : 13, programmed : 70000, actual : 0 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 SimpleTimer : 2, ms : 40341, Dms : 10055 Timer : 0, programmed : 5000, actual : 5000 Timer : 1, programmed : 10000, actual : 10000 Timer : 2, programmed : 15000, actual : 15000 Timer : 3, programmed : 20000, actual : 20000 Timer : 4, programmed : 25000, actual : 25008 Timer : 5, programmed : 30000, actual : 30008 Timer : 6, programmed : 35000, actual : 35008 Timer : 7, programmed : 40000, actual : 40008 Timer : 8, programmed : 45000, actual : 0 Timer : 9, programmed : 50000, actual : 0 Timer : 10, programmed : 55000, actual : 0 Timer : 11, programmed : 60000, actual : 0 Timer : 12, programmed : 65000, actual : 0 Timer : 13, programmed : 70000, actual : 0 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 SimpleTimer : 2, ms : 50396, Dms : 10055 Timer : 0, programmed : 5000, actual : 5000 Timer : 1, programmed : 10000, actual : 10000 Timer : 2, programmed : 15000, actual : 15000 Timer : 3, programmed : 20000, actual : 20000 Timer : 4, programmed : 25000, actual : 25000 Timer : 5, programmed : 30000, actual : 30008 Timer : 6, programmed : 35000, actual : 35008 Timer : 7, programmed : 40000, actual : 40008 Timer : 8, programmed : 45000, actual : 45008 Timer : 9, programmed : 50000, actual : 50008 Timer : 10, programmed : 55000, actual : 0 Timer : 11, programmed : 60000, actual : 0 Timer : 12, programmed : 65000, actual : 0 Timer : 13, programmed : 70000, actual : 0 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 SimpleTimer : 2, ms : 60452, Dms : 10056 Timer : 0, programmed : 5000, actual : 5000 Timer : 1, programmed : 10000, actual : 10000 Timer : 2, programmed : 15000, actual : 15000 Timer : 3, programmed : 20000, actual : 20000 Timer : 4, programmed : 25000, actual : 25000 Timer : 5, programmed : 30000, actual : 30000 Timer : 6, programmed : 35000, actual : 35008 Timer : 7, programmed : 40000, actual : 40008 Timer : 8, programmed : 45000, actual : 45008 Timer : 9, programmed : 50000, actual : 50008 Timer : 10, programmed : 55000, actual : 55008 Timer : 11, programmed : 60000, actual : 60008 Timer : 12, programmed : 65000, actual : 0 Timer : 13, programmed : 70000, actual : 0 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 SimpleTimer : 2, ms : 70509, Dms : 10057 Timer : 0, programmed : 5000, actual : 5000 Timer : 1, programmed : 10000, actual : 10000 Timer : 2, programmed : 15000, actual : 15000 Timer : 3, programmed : 20000, actual : 20000 Timer : 4, programmed : 25000, actual : 25000 Timer : 5, programmed : 30000, actual : 30000 Timer : 6, programmed : 35000, actual : 35000 Timer : 7, programmed : 40000, actual : 40008 Timer : 8, programmed : 45000, actual : 45008 Timer : 9, programmed : 50000, actual : 50008 Timer : 10, programmed : 55000, actual : 55008 Timer : 11, programmed : 60000, actual : 60008 Timer : 12, programmed : 65000, actual : 65008 Timer : 13, programmed : 70000, actual : 70008 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 SimpleTimer : 2, ms : 80566, Dms : 10057 Timer : 0, programmed : 5000, actual : 5000 Timer : 1, programmed : 10000, actual : 10000 Timer : 2, programmed : 15000, actual : 15000 Timer : 3, programmed : 20000, actual : 20000 Timer : 4, programmed : 25000, actual : 25000 Timer : 5, programmed : 30000, actual : 30000 Timer : 6, programmed : 35000, actual : 35000 Timer : 7, programmed : 40000, actual : 40000 Timer : 8, programmed : 45000, actual : 45008 Timer : 9, programmed : 50000, actual : 50008 Timer : 10, programmed : 55000, actual : 55008 Timer : 11, programmed : 60000, actual : 60008 Timer : 12, programmed : 65000, actual : 65008 Timer : 13, programmed : 70000, actual : 70008 Timer : 14, programmed : 75000, actual : 75008 Timer : 15, programmed : 80000, actual : 80008

5. ISR_16_Timers_Array_OneShot on ESP8266_NODEMCU_ESP12E

The following is the sample terminal output when running example ISR_16_Timers_Array_OneShot on ESP8266_NODEMCU_ESP12E to demonstrate the One-Shot ISR Hardware Timer, especially when system is very busy or blocked. The 16 independent ISR timers are programmed to be activated repetitively after certain intervals, is activated exactly after that programmed interval !!!

Starting ISR_16_Timers_Array_OneShot on ESP8266_NODEMCU_ESP12E ESP8266TimerInterrupt v1.6.0 CPU Frequency = 160 MHz Starting ITimer OK, millis() = 365 1s: Delta ms = 1002, ms = 1367 2s: Delta ms = 2002, ms = 2367 3s: Delta ms = 3002, ms = 3367 4s: Delta ms = 4002, ms = 4367 5s: Delta ms = 5002, ms = 5367 6s: Delta ms = 6002, ms = 6367 7s: Delta ms = 7002, ms = 7367 8s: Delta ms = 8002, ms = 8367 9s: Delta ms = 9002, ms = 9367 10s: Delta ms = 10002, ms = 10367 simpleTimerDoingSomething2s: Delta programmed ms = 2000, actual = 10002 11s: Delta ms = 11002, ms = 11367 12s: Delta ms = 12002, ms = 12367 13s: Delta ms = 13002, ms = 13367 14s: Delta ms = 14002, ms = 14367 15s: Delta ms = 15002, ms = 15367 16s: Delta ms = 16002, ms = 16367 simpleTimerDoingSomething2s: Delta programmed ms = 2000, actual = 10000 simpleTimerDoingSomething2s: Delta programmed ms = 2000, actual = 10000 simpleTimerDoingSomething2s: Delta programmed ms = 2000, actual = 10001 simpleTimerDoingSomething2s: Delta programmed ms = 2000, actual = 10000 simpleTimerDoingSomething2s: Delta programmed ms = 2000, actual = 10000 simpleTimerDoingSomething2s: Delta programmed ms = 2000, actual = 10000 simpleTimerDoingSomething2s: Delta programmed ms = 2000, actual = 10000

Debug

Debug is enabled by default on Serial.

You can also change the debugging level (TIMERINTERRUPT_LOGLEVEL) from 0 to 4

// These define's must be placed at the beginning before #include "ESP8266TimerInterrupt.h" // _TIMERINTERRUPT_LOGLEVEL_ from 0 to 4 // Don't define _TIMERINTERRUPT_LOGLEVEL_ > 0. Only for special ISR debugging only. Can hang the system. #define TIMER_INTERRUPT_DEBUG 0 #define _TIMERINTERRUPT_LOGLEVEL_ 0

Troubleshooting

If you get compilation errors, more often than not, you may need to install a newer version of the core for Arduino boards.

Sometimes, the library will only work if you update the board core to the latest version because I am using newly added functions.

Issues

Submit issues to: ESP8266TimerInterrupt issues

TO DO

  1. Search for bug and improvement.

DONE

  1. Basic hardware timers for ESP8266.
  2. More hardware-initiated software-enabled timers
  3. Longer time interval
  4. Similar features for remaining Arduino boards such as AVR, Teensy, SAMD21, SAMD51, SAM-DUE, nRF52, ESP32, STM32, etc.
  5. Update to match new ESP8266 core v3.0.0
  6. Fix compiler errors due to conflict to some libraries.
  7. Add complex examples.
  8. Update to match new ESP8266 core v3.0.2
  9. Fix multiple-definitions linker error. Drop src_cpp and src_h directories
  10. Add feature to select among highest, medium or lowest accuracy for Timers for shortest, medium or longest time
  11. Convert to h-only style.
  12. Optimize code by using passing by reference instead of by value
  13. Add example multiFileProject to demo for multiple-file project
  14. Add example ISR_16_Timers_Array_OneShot to demo how to use one-shot ISR-based timer

Contributions and thanks

  1. Thanks to Holger Lembke to report ESP8266TimerInterrupt Issue 8: ESP8266Timer and PWM --> wdt reset, leading to the HOWTO Use PWM analogWrite() with ESP8266 running Timer1 Interrupt notes.
  2. Thanks to Eugene to make bug-fixing PR and discussion in bugfix: reattachInterrupt() pass wrong frequency value to setFrequency() #19, leading to v1.5.0
  3. Thanks to absalom-muc to make enhancement request in One shot operating mode #20, leading to v1.6.0 to add example to demo how to use one-shot ISR-based timer
holgerlembke
Holger Lembke
 RushOnline
Eugene
 absalom-muc
absalom-muc

Contributing

If you want to contribute to this project:

  • Report bugs and errors
  • Ask for enhancements
  • Create issues and pull requests
  • Tell other people about this library

License

  • The library is licensed under MIT

Copyright

Copyright 2019- Khoi Hoang

About

This library enables you to use Interrupt from Hardware Timers on an ESP8266-based board. It now supports 16 ISR-based timers, while consuming only 1 hardware Timer. Timers' interval is very long (ulong millisecs). The most important feature is they're ISR-based timers. Therefore, their executions are not blocked by bad-behaving functions or tas…

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arduino esp8266 board delay wifi accuracy espressif isr non-blocking timers interrupt esp8266-arduino millis mission-critical arduino-libraries hardware-timers timerinterrupt timerinterrupt-library isr-based-timer one-shot-timer

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v1.6.0 to optimize code by using passing by `reference` instead of by `value`, to add examples to demo one-shot timer and multiple-file projects Latest
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