1. Add example using Blynk to control servos.
2. Change example names to avoid duplication.

1. Basic 16 ISR-based servo controllers using 1 hardware timer for ESP8266.

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

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.

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

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.

1. Arduino IDE 1.8.13+
2. ESP8266 core 2.7.4+ for ESP8266 boards.

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.

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/.

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

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.

1. Add functions getPosition() and getPulseWidth()
2. Optimize the code
3. Add more complicated example

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

• ESP8266

How to use:

#define TIMER_INTERRUPT_DEBUG 1 #define ISR_SERVO_DEBUG 1 #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); Serial.println("\nStarting"); servoIndex1 = ISR_Servo.setupServo(D8, MIN_MICROS, MAX_MICROS); servoIndex2 = ISR_Servo.setupServo(D7, MIN_MICROS, MAX_MICROS); if (servoIndex1 != -1) Serial.println("Setup Servo1 OK"); else Serial.println("Setup Servo1 failed"); if (servoIndex2 != -1) Serial.println("Setup Servo2 OK"); else Serial.println("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 ISR_Servo.setPosition(servoIndex1, position); ISR_Servo.setPosition(servoIndex2, 180 - position); // waits 50ms for the servo to reach the position delay(50 /*15*/); } 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 50ms for the servo to reach the position delay(50 /*15*/); } } } 

1. ESP8266_BlynkServoControl
2. ESP8266_ISR_MultiServos
3. ESP8266_MultipleRandomServos
4. ESP8266_MultipleServos
5. ISR_MultiServos
6. MultipleRandomServos
7. MultipleServos

#ifndef ESP8266 #error This code is designed to run on ESP8266 platform, not Arduino nor ESP32! Please check your Tools->Board setting. #endif #define BLYNK_PRINT Serial //See file .../hardware/espressif/esp32/variants/(esp32|doitESP32devkitV1)/pins_arduino.h #define LED_BUILTIN 2 // Pin D4 mapped to pin GPIO2/TXD1 of ESP8266, NodeMCU and WeMoS, control on-board LED //PIN_D0 can't be used for PWM/I2C #define PIN_D0 16 // Pin D0 mapped to pin GPIO16/USER/WAKE of ESP8266. This pin is also used for Onboard-Blue LED. PIN_D0 = 0 => LED ON #define PIN_D1 5 // Pin D1 mapped to pin GPIO5 of ESP8266 #define PIN_D2 4 // Pin D2 mapped to pin GPIO4 of ESP8266 #define PIN_D3 0 // Pin D3 mapped to pin GPIO0/FLASH of ESP8266 #define PIN_D4 2 // Pin D4 mapped to pin GPIO2/TXD1 of ESP8266 #define PIN_LED 2 // Pin D4 mapped to pin GPIO2/TXD1 of ESP8266, NodeMCU and WeMoS, control on-board LED #define PIN_D5 14 // Pin D5 mapped to pin GPIO14/HSCLK of ESP8266 #define PIN_D6 12 // Pin D6 mapped to pin GPIO12/HMISO of ESP8266 #define PIN_D7 13 // Pin D7 mapped to pin GPIO13/RXD2/HMOSI of ESP8266 #define PIN_D8 15 // Pin D8 mapped to pin GPIO15/TXD2/HCS of ESP8266 #define USE_SPIFFS true //#define USE_SPIFFS false #define USE_BLYNK_WM true // https://github.com/khoih-prog/Blynk_WM //#define USE_BLYNK_WM false //LIBRARIES INCLUDED #include <ESP8266WiFi.h> #if USE_BLYNK_WM #include <BlynkSimpleEsp8266_WM.h> // https://github.com/khoih-prog/Blynk_WM #else #include <BlynkSimpleEsp8266.h> //BLYNK AUTHENTICATION TOKEN char auth[] = "******"; // MY WIFI CREDENTIALS char ssid[] = "****"; char pass[] = "****"; #endif #define TIMER_INTERRUPT_DEBUG 1 #define ISR_SERVO_DEBUG 1 #include "ESP8266_ISR_Servo.h" // MG996R servo has a running current of 500mA to 900mA @6V and a stall current of 2.5A @ 6V // Power supply must be adequate // Published values for SG90 servos; adjust if needed #define MIN_MICROS 800 //544 #define MAX_MICROS 2450 int servoIndex1 = -1; int servoIndex2 = -1; int servoIndex3 = -1; int servo1Pin = PIN_D6; //SERVO1 PIN int servo2Pin = PIN_D7; //SERVO2 PIN int servo3Pin = PIN_D8; //SERVO3 PIN BlynkTimer timer; // These are Blynk Slider or any Widget (STEP, Numeric Input, being able to output (unsigned) int value from 0-180. // You have to map from 0-180 inside widget or in your code. Otherwise, the library will remap the input for you. #define BLYNK_VPIN_SERVO1_CONTROL V21 #define BLYNK_VPIN_SERVO2_CONTROL V22 #define BLYNK_VPIN_SERVO3_CONTROL V23 //READING FROM VIRTUAL PINS // SERVO1 BLYNK_WRITE(BLYNK_VPIN_SERVO1_CONTROL) { ISR_Servo.setPosition(servoIndex1, param.asInt()); } //SERVO2 BLYNK_WRITE(BLYNK_VPIN_SERVO2_CONTROL) { ISR_Servo.setPosition(servoIndex2, param.asInt()); } //SERVO3 BLYNK_WRITE(BLYNK_VPIN_SERVO3_CONTROL) { ISR_Servo.setPosition(servoIndex3, param.asInt()); } void heartBeatPrint(void) { static int num = 1; if (WiFi.status() == WL_CONNECTED) { if (Blynk.connected()) Serial.print("B"); // B means connected to Blynk else Serial.print("H"); // H means connected to WiFi but no Blynk } else Serial.print("F"); // F means not connected to WiFi and Blynk if (num == 80) { Serial.println(); num = 1; } else if (num++ % 10 == 0) { Serial.print(" "); } } void setup() { // Debug console Serial.begin(115200); Serial.println("\nStarting"); #if USE_BLYNK_WM Blynk.begin(); #else Blynk.begin(auth, ssid, pass); #endif servoIndex1 = ISR_Servo.setupServo(servo1Pin, MIN_MICROS, MAX_MICROS); servoIndex2 = ISR_Servo.setupServo(servo2Pin, MIN_MICROS, MAX_MICROS); servoIndex3 = ISR_Servo.setupServo(servo3Pin, MIN_MICROS, MAX_MICROS); if (servoIndex1 != -1) Serial.println("Setup Servo1 OK"); else Serial.println("Setup Servo1 failed"); if (servoIndex2 != -1) Serial.println("Setup Servo2 OK"); else Serial.println("Setup Servo2 failed"); if (servoIndex3 != -1) Serial.println("Setup Servo3 OK"); else Serial.println("Setup Servo3 failed"); timer.setInterval(30000L, heartBeatPrint); } void loop() { Blynk.run(); timer.run(); }

1. Search for bug and improvement.

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

1. Add example using Blynk to control servos.
2. Change example names to avoid duplication.

1. Basic 16 ISR-based servo controllers using 1 hardware timer for ESP8266.

Submit issues to: ESP8266_ISR_Servo issues

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

• The library is licensed under MIT

Copyright 2019- Khoi Hoang