ESP8266TimerInterrupt Library

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Table of Contents

• Important Change from v1.6.0
• Why do we need this ESP8266TimerInterrupt library
  • Features
  • Why using ISR-based Hardware Timer Interrupt is better
  • Currently supported Boards
  • Important Notes about ISR
• Changelog
• Prerequisites
• Installation
  • Use Arduino Library Manager
  • Manual Install
  • VS Code & PlatformIO
• HOWTO Fix Multiple Definitions Linker Error
• HOWTO Use PWM analogWrite() with ESP8266 running Timer1 Interrupt
  • 1. ESP8266 has only 2 hardware timers, named Timer0 and Timer1
  • 2. ESP8266 hardware timers' functions
  • 3. How to use PWM analogWrite() functions while using this library
• More useful Information
• Usage
  • 1. Using only Hardware Timer directly
    • 1.1 Init Hardware Timer
    • 1.2 Set Hardware Timer Interval and attach Timer Interrupt Handler function
    • 1.3 Set Hardware Timer Frequency and attach Timer Interrupt Handler function
  • 2. Using 16 ISR_based Timers from 1 Hardware Timer
    • 2.1 Important Note
    • 2.2 Init Hardware Timer and ISR-based Timer
    • 2.3 Set Hardware Timer Interval and attach Timer Interrupt Handler functions
    • 2.4 Set One-Shot Hardware Timer Interval
• Examples
  • 1. Argument_None
  • 2. Change_Interval.
  • 3. ISR_RPM_Measure
  • 4. RPM_Measure
  • 5. SwitchDebounce
  • 6. TimerInterruptTest
  • 7. ISR_16_Timers_Array
  • 8. ISR_16_Timers_Array_Complex
  • 9. ISR_16_Timers_Array_OneShot New
  • 10. multiFileProject New
• Example Change_Interval
• Debug Terminal Output Samples
  • 1. TimerInterruptTest on ESP8266_NODEMCU_ESP12E
  • 2. Change_Interval on ESP8266_NODEMCU_ESP12E
  • 3. ISR_16_Timers_Array on ESP8266_NODEMCU_ESP12E
  • 4. ISR_16_Timers_Array_Complex on ESP8266_NODEMCU_ESP12E
  • 5. ISR_16_Timers_Array_OneShot on ESP8266_NODEMCU_ESP12E
• Debug
• Troubleshooting
• Issues
• TO DO
• DONE
• Contributions and Thanks
• Contributing
• License
• Copyright

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Important Change from v1.6.0

Please have a look at HOWTO Fix Multiple Definitions Linker Error

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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

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Currently supported Boards

1. ESP8266-based boards

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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.

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Prerequisites

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

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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 fo