ESP8266_ISR_Servo Library

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Table of Contents

• Important Change from v1.3.0
• Why do we need this ESP8266_ISR_Servo library
  • Features
  • Important Notes about using ISR
  • Currently supported Boards
• Changelog
• Prerequisites
• Installation
  • Use Arduino Library Manager
  • Manual Install
  • VS Code & PlatformIO
• HOWTO Fix Multiple Definitions Linker Error
• More useful Information
  • ESP8266 Hardware Timers
  • New functions
  • What special in this ESP8266_ISR_Servo library
• HOWTO Usage
• Examples
  • 1. multiFileProject New
  • 2. ESP8266_ISR_MultiServos
  • 3. ESP8266_MultipleRandomServos
  • 4. ESP8266_MultipleServos
  • 5. ISR_MultiServos
  • 6. MultipleRandomServos
  • 7. MultipleServos
• Example ESP8266_MultipleRandomServos
• Debug Terminal Output Samples
  • 1. ESP8266_MultipleRandomServos on ESP8266_NODEMCU_ESP12E
  • 2. ESP8266_ISR_MultiServos on ESP8266_NODEMCU_ESP12E
• Debug
• Troubleshooting
• Issues
• TO DO
• DONE
• Contributions and Thanks
• Contributing
• License
• Copyright

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Important Change from v1.3.0

Please have a look at HOWTO Fix Multiple Definitions Linker Error

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Why do we need this ESP8266_ISR_Servo library

Features

Imagine you have a system with a mission-critical function controlling a robot arm 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.

This library enables you to use 1 Hardware Timer on an ESP8266-based board to control up to 16 independent servo motors.

Important Notes about using 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.

3. Avoid using Serial.print()-related functions inside ISR. Just for temporary debug purpose, but even this also can crash the system any time. Beware.

4. Your functions are now part of ISR (Interrupt Service Routine), and must be lean / mean, and follow certain rules. More to read on:

HOWTO Attach Interrupt

Currently supported Boards

This ESP8266_ISR_Servo library currently supports these following boards:

1. ESP8266-based boards.

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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.

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Installation

Use Arduino Library Manager

The best and easiest way is to use Arduino Library Manager. Search for ESP8266_ISR_Servo, then select / install the latest version. You can also use this link for more detailed instructions.

Manual Install

Another way to install is to:

1. Navigate to ESP8266_ISR_Servo page.
2. Download the latest release ESP8266_ISR_Servo-master.zip.
3. Extract the zip file to ESP8266_ISR_Servo-master directory
4. Copy whole ESP8266_ISR_Servo-master folder to Arduino libraries' directory such as ~/Arduino/libraries/.

VS Code & PlatformIO

1. Install VS Code
2. Install PlatformIO
3. Install ESP8266_ISR_Servo library by using Library Manager. Search for ESP8266_ISR_Servo 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

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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 include this .hpp file

// Can be included as many times as necessary, without `Multiple Definitions` Linker Error
#include "ESP8266_ISR_Servo.hpp"     //https://github.com/khoih-prog/ESP8266_ISR_Servo

in many files. But be sure to use the following .h file 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_Servo.h"           //https://github.com/khoih-prog/ESP8266_ISR_Servo

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

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More useful Information

ESP8266 Hardware Timers

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 !!!

The timer1 counters can be configured to support automatic reload.

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New functions

// returns last position in degrees if success, or -1 on wrong servoIndex
int getPosition(unsigned servoIndex);

// returns pulseWidth in microsecs (within min/max range) if success, or 0 on wrong servoIndex
unsigned int getPulseWidth(unsigned servoIndex);

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What special in this ESP8266_ISR_Servo library

Now these new 16 ISR-based Servo controllers just use one ESP8266 Hardware Timer. The number 16 is just arbitrarily chosen, and depending on application, you can increase that number to 32, 48, etc. without problem.

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 MultipleServos example, which controls 6 servos independently, will demonstrate the nearly perfect accuracy. Being ISR-based servo controllers, their executions are not blocked by bad-behaving functions / tasks, such as connecting to WiFi, Internet and Blynk services.

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

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HOWTO Usage

How to use:

ESP8266_ISR_Servo/examples/ESP8266_ISR_MultiServos/ESP8266_ISR_MultiServos.ino

Lines 70 to 151 in 114dc0c

	#ifndef ESP8266
	#error This code is designed to run on ESP8266 platform! Please check your Tools->Board setting.
	#endif
	#define TIMER_INTERRUPT_DEBUG 1
	#define ISR_SERVO_DEBUG 1
	// To be included only in main(), .ino with setup() to avoid `Multiple Definitions` Linker Error
	#include "ESP8266_ISR_Servo.h"
	// Published values for SG90 servos; adjust if needed
	#define MIN_MICROS 800 //544
	#define MAX_MICROS 2450
	int servoIndex1 = -1;
	int servoIndex2 = -1;
	void setup()
	{
	Serial.begin(115200);
	while (!Serial);
	delay(200);
	Serial.print(F("\nStarting ESP8266_ISR_MultiServos on "));
	Serial.println(ARDUINO_BOARD);
	Serial.println(ESP8266_ISR_SERVO_VERSION);
	servoIndex1 = ISR_Servo.setupServo(D8, MIN_MICROS, MAX_MICROS);
	servoIndex2 = ISR_Servo.setupServo(D7, MIN_MICROS, MAX_MICROS);
	if (servoIndex1 != -1)
	Serial.println(F("Setup Servo1 OK"));
	else
	Serial.println(F("Setup Servo1 failed"));
	if (servoIndex2 != -1)
	Serial.println(F("Setup Servo2 OK"));
	else
	Serial.println(F("Setup Servo2 failed"));
	}
	void loop()
	{
	int position;
	if ( ( servoIndex1 != -1) && ( servoIndex2 != -1) )
	{
	for (position = 0; position <= 180; position++)
	{
	// goes from 0 degrees to 180 degrees
	// in steps of 1 degree
	if (position % 30 == 0)
	{
	Serial.print(F("Servo1 pos = "));
	Serial.print(position);
	Serial.print(F(", Servo2 pos = "));
	Serial.println(180 - position);
	}
	ISR_Servo.setPosition(servoIndex1, position);
	ISR_Servo.setPosition(servoIndex2, 180 - position);
	// waits 15ms for the servo to reach the position
	delay(50 /*15*/);
	}
	delay(5000);
	for (position = 180; position >= 0; position--)
	{
	// goes from 180 degrees to 0 degrees
	ISR_Servo.setPosition(servoIndex1, position);
	ISR_Servo.setPosition(servoIndex2, 180 - position);
	// waits 15ms for the servo to reach the position
	delay(50 /*15*/);
	}
	delay(5000);
	}
	}

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Examples:

1. multiFileProject New
2. ESP8266_ISR_MultiServos
3. ESP8266_MultipleRandomServos
4. ESP8266_MultipleServos
5. ISR_MultiServos
6. MultipleRandomServos
7. MultipleServos

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Example ESP8266_MultipleRandomServos

ESP8266_ISR_Servo/examples/ESP8266_MultipleRandomServos/ESP8266_MultipleRandomServos.ino

Lines 61 to 237 in 114dc0c

	#ifndef ESP8266
	#error This code is designed to run on ESP8266 platform! Please check your Tools->Board setting.
	#endif
	#define TIMER_INTERRUPT_DEBUG 1
	#define ISR_SERVO_DEBUG 0
	// To be included only in main(), .ino with setup() to avoid `Multiple Definitions` Linker Error
	#include "ESP8266_ISR_Servo.h"
	// Published values for SG90 servos; adjust if needed
	#define MIN_MICROS 800 //544
	#define MAX_MICROS 2450
	#define NUM_SERVOS 6
	typedef struct
	{
	int servoIndex;
	uint8_t servoPin;
	} ISR_servo_t;
	ISR_servo_t ISR_servo[NUM_SERVOS] =
	{
	{ -1, D0 }, { -1, D1 }, { -1, D2 }, { -1, D5 }, { -1, D6 }, { -1, D7 }
	};
	void setup()
	{
	Serial.begin(115200);
	while (!Serial);
	delay(200);
	Serial.print(F("\nStarting ESP8266_MultipleRandomServos on "));
	Serial.println(ARDUINO_BOARD);
	Serial.println(ESP8266_ISR_SERVO_VERSION);
	for (int index = 0; index < NUM_SERVOS; index++)
	{
	ISR_servo[index].servoIndex = ISR_Servo.setupServo(ISR_servo[index].servoPin, MIN_MICROS, MAX_MICROS);
	if (ISR_servo[index].servoIndex != -1)
	{
	Serial.print(F("Setup OK Servo index = "));
	Serial.println(ISR_servo[index].servoIndex);
	}
	else
	{
	Serial.print(F("Setup Failed Servo index = "));
	Serial.println(ISR_servo[index].servoIndex);
	}
	}
	}
	void printServoInfo(int indexServo)
	{
	Serial.print(F("Servos idx = "));
	Serial.print(indexServo);
	Serial.print(F(", act. pos. (deg) = "));
	Serial.print(ISR_Servo.getPosition(ISR_servo[indexServo].servoIndex) );
	Serial.print(F(", pulseWidth (us) = "));
	Serial.println(ISR_Servo.getPulseWidth(ISR_servo[indexServo].servoIndex));
	}
	void loop()
	{
	int position; // position in degrees
	position = 0;
	Serial.println(F("Servos @ 0 degree"));
	for (int index = 0; index < NUM_SERVOS; index++)
	{
	ISR_Servo.setPosition(ISR_servo[index].servoIndex, position );
	printServoInfo(index);
	}
	// waits 5s between test
	delay(5000);
	position = 90;
	Serial.println(F("Servos @ 90 degree"));
	for (int index = 0; index < NUM_SERVOS; index++)
	{
	ISR_Servo.setPosition(ISR_servo[index].servoIndex, position );
	printServoInfo(index);
	}
	// waits 5s between test
	delay(5000);
	position = 180;
	Serial.println(F("Servos @ 180 degree"));
	for (int index = 0; index < NUM_SERVOS; index++)
	{
	ISR_Servo.setPosition(ISR_servo[index].servoIndex, position );
	printServoInfo(index);
	}
	// waits 5s between test
	delay(5000);
	Serial.println(F("Servos sweeps from 0-180 degress"));
	for (position = 0; position <= 180; position += 1)
	{
	// goes from 0 degrees to 180 degrees
	// in steps of 1 degree
	for (int index = 0; index < NUM_SERVOS; index++)
	{
	ISR_Servo.setPosition(ISR_servo[index].servoIndex, position );
	}
	// waits 50ms for the servo to reach the position
	delay(50);
	}
	// waits 5s between test
	delay(5000);
	Serial.println(F("Servos sweeps from 180-0 degress"));
	for (position = 180; position >= 0; position -= 1)
	{
	// goes from 0 degrees to 180 degrees
	// in steps of 1 degree
	for (int index = 0; index < NUM_SERVOS; index++)
	{
	ISR_Servo.setPosition(ISR_servo[index].servoIndex, position );
	}
	// waits 50ms for the servo to reach the position
	delay(50);
	}
	// waits 5s between test
	delay(5000);
	Serial.println(F("Servos, index depending, be somewhere from 0-180 degress"));
	for (position = 0; position <= 180; position += 1)
	{
	// goes from 0 degrees to 180 degrees
	// in steps of 1 degree
	for (int index = 0; index < NUM_SERVOS; index++)
	{
	ISR_Servo.setPosition(ISR_servo[index].servoIndex, (position + index * (180 / NUM_SERVOS)) % 180 );
	}
	// waits 50ms for the servo to reach the position
	delay(50);
	}
	delay(5000);
	Serial.println(F("Servos, index depending, be somewhere from 180-0 degress"));
	for (position = 180; position >= 0; position -= 1)
	{
	// goes from 0 degrees to 180 degrees
	// in steps of 1 degree
	for (int index = 0; index < NUM_SERVOS; index++)
	{
	ISR_Servo.setPosition(ISR_servo[index].servoIndex, (position + index * (180 / NUM_SERVOS)) % 180 );
	}
	// waits 50ms for the servo to reach the position
	delay(50);
	}
	// waits 5s between test
	delay(5000);
	}

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Debug Terminal Output Samples

1. ESP8266_MultipleRandomServos on ESP8266_NODEMCU_ESP12E

Starting ESP8266_MultipleRandomServos on ESP8266_NODEMCU_ESP12E
ESP8266_ISR_Servo v1.3.0
[ISR_SERVO] ESP8266FastTimerInterrupt: _fre = 5000000.00 , _count = 50
[ISR_SERVO] Starting  ITimer OK
Setup OK Servo index = 0
Setup OK Servo index = 1
Setup OK Servo index = 2
Setup OK Servo index = 3
Setup OK Servo index = 4
Setup OK Servo index = 5
Servos @ 0 degree
[ISR_SERVO] Idx = 0
[ISR_SERVO] cnt = 80 , pos = 0
Servos idx = 0, act. pos. (deg) = [ISR_SERVO] Idx = 0
[ISR_SERVO] cnt = 80 , pos = 0
0, pulseWidth (us) = [ISR_SERVO] Idx = 0
[ISR_SERVO] cnt = 80 , pos = 0
800
[ISR_SERVO] Idx = 1
[ISR_SERVO] cnt = 80 , pos = 0
Servos idx = 1, act. pos. (deg) = [ISR_SERVO] Idx = 1
[ISR_SERVO] cnt = 80 , pos = 0
0, pulseWidth (us) = [ISR_SERVO] Idx = 1
[ISR_SERVO] cnt = 80 , pos = 0
800
[ISR_SERVO] Idx = 2
[ISR_SERVO] cnt = 80 , pos = 0
Servos idx = 2, act. pos. (deg) = [ISR_SERVO] Idx = 2
[ISR_SERVO] cnt = 80 , pos = 0
0, pulseWidth (us) = [ISR_SERVO] Idx = 2
[ISR_SERVO] cnt = 80 , pos = 0
800
[ISR_SERVO] Idx = 3
[ISR_SERVO] cnt = 80 , pos = 0
Servos idx = 3, act. pos. (deg) = [ISR_SERVO] Idx = 3
[ISR_SERVO] cnt = 80 , pos = 0
0, pulseWidth (us) = [ISR_SERVO] Idx = 3
[ISR_SERVO] cnt = 80 , pos = 0
800
[ISR_SERVO] Idx = 4
[ISR_SERVO] cnt = 80 , pos = 0
Servos idx = 4, act. pos. (deg) = [ISR_SERVO] Idx = 4
[ISR_SERVO] cnt = 80 , pos = 0
0, pulseWidth (us) = [ISR_SERVO] Idx = 4
[ISR_SERVO] cnt = 80 , pos = 0
800
[ISR_SERVO] Idx = 5
[ISR_SERVO] cnt = 80 , pos = 0
Servos idx = 5, act. pos. (deg) = [ISR_SERVO] Idx = 5
[ISR_SERVO] cnt = 80 , pos = 0
0, pulseWidth (us) = [ISR_SERVO] Idx = 5
[ISR_SERVO] cnt = 80 , pos = 0
800
Servos @ 90 degree
[ISR_SERVO] Idx = 0
[ISR_SERVO] cnt = 162 , pos = 90
Servos idx = 0, act. pos. (deg) = [ISR_SERVO] Idx = 0
[ISR_SERVO] cnt = 162 , pos = 90
90, pulseWidth (us) = [ISR_SERVO] Idx = 0
[ISR_SERVO] cnt = 162 , pos = 90
1620
[ISR_SERVO] Idx = 1
[ISR_SERVO] cnt = 162 , pos = 90
Servos idx = 1, act. pos. (deg) = [ISR_SERVO] Idx = 1
[ISR_SERVO] cnt = 162 , pos = 90
90, pulseWidth (us) = [ISR_SERVO] Idx = 1
[ISR_SERVO] cnt = 162 , pos = 90
1620
[ISR_SERVO] Idx = 2
[ISR_SERVO] cnt = 162 , pos = 90
Servos idx = 2, act. pos. (deg) = [ISR_SERVO] Idx = 2
[ISR_SERVO] cnt = 162 , pos = 90
90, pulseWidth (us) = [ISR_SERVO] Idx = 2
[ISR_SERVO] cnt = 162 , pos = 90
1620
[ISR_SERVO] Idx = 3
[ISR_SERVO] cnt = 162 , pos = 90
Servos idx = 3, act. pos. (deg) = [ISR_SERVO] Idx = 3
[ISR_SERVO] cnt = 162 , pos = 90
90, pulseWidth (us) = [ISR_SERVO] Idx = 3
[ISR_SERVO] cnt = 162 , pos = 90
1620
[ISR_SERVO] Idx = 4
[ISR_SERVO] cnt = 162 , pos = 90
Servos idx = 4, act. pos. (deg) = [ISR_SERVO] Idx = 4
[ISR_SERVO] cnt = 162 , pos = 90
90, pulseWidth (us) = [ISR_SERVO] Idx = 4
[ISR_SERVO] cnt = 162 , pos = 90
1620
[ISR_SERVO] Idx = 5
[ISR_SERVO] cnt = 162 , pos = 90
Servos idx = 5, act. pos. (deg) = [ISR_SERVO] Idx = 5
[ISR_SERVO] cnt = 162 , pos = 90
90, pulseWidth (us) = [ISR_SERVO] Idx = 5
[ISR_SERVO] cnt = 162 , pos = 90
1620

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2. ESP8266_ISR_MultiServos on ESP8266_NODEMCU_ESP12E

Starting ESP8266_ISR_MultiServos on ESP8266_NODEMCU_ESP12E
ESP8266_ISR_Servo v1.3.0
[ISR_SERVO] ESP8266FastTimerInterrupt: _fre = 5000000.00 , _count = 50
[ISR_SERVO] Starting  ITimer OK
Setup Servo1 OK
Setup Servo2 OK
Servo1 pos = 0, Servo2 pos = 180
[ISR_SERVO] Idx = 0
[ISR_SERVO] cnt = 80 , pos = 0
[ISR_SERVO] Idx = 1
[ISR_SERVO] cnt = 245 , pos = 180
[ISR_SERVO] Idx = 0
[ISR_SERVO] cnt = 80 , pos = 1
[ISR_SERVO] Idx = 1
[ISR_SERVO] cnt = 244 , pos = 179
[ISR_SERVO] Idx = 0
[ISR_SERVO] cnt = 81 , pos = 2
[ISR_SERVO] Idx = 1
[ISR_SERVO] cnt = 243 , pos = 178
[ISR_SERVO] Idx = 0
[ISR_SERVO] cnt = 82 , pos = 3
[ISR_SERVO] Idx = 1
[ISR_SERVO] cnt = 242 , pos = 177
[ISR_SERVO] Idx = 0
[ISR_SERVO] cnt = 83 , pos = 4
[ISR_SERVO] Idx = 1
[ISR_SERVO] cnt = 241 , pos = 176
[ISR_SERVO] Idx = 0
[ISR_SERVO] cnt = 84 , pos = 5
[ISR_SERVO] Idx = 1
[ISR_SERVO] cnt = 240 , pos = 175
[ISR_SERVO] Idx = 0
[ISR_SERVO] cnt = 85 , pos = 6
[ISR_SERVO] Idx = 1
[ISR_SERVO] cnt = 239 , pos = 174
[ISR_SERVO] Idx = 0
[ISR_SERVO] cnt = 86 , pos = 7
[ISR_SERVO] Idx = 1
[ISR_SERVO] cnt = 238 , pos = 173

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Debug

Debug is enabled by default on Serial.

You can also change the debugging level from 0 to 2. Be careful and using level 2 only for temporary debug purpose only.

#define TIMER_INTERRUPT_DEBUG       1
#define ISR_SERVO_DEBUG             1

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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.

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Issues

Submit issues to: ESP8266_ISR_Servo issues

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TO DO

1. Search for bug and improvement.

DONE

1. Similar features for Arduino (UNO, Mega, etc...) and ESP32
2. Add functions getPosition() and getPulseWidth()
3. Optimize the code
4. Add more complicated examples
5. Update to match new ESP8266 core v3.0.0
6. Convert to h-only style.
7. Add example multiFileProject to demo for multiple-file project
8. Optimize code by using passing by reference instead of by value
9. Add astyle using allman style. Restyle the library

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Contributions and Thanks

1. Thanks to raphweb for the PR Fixed count >= min comparison for servo enable. to fix bug and leading to the new releases v1.1.0

⭐️ raphweb

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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

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License

• The library is licensed under MIT

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Copyright

Copyright (c) 2019- Khoi Hoang