- Why do we need this ESP8266_ISR_Servo library
- Changelog
- Prerequisites
- Installation
- More useful Information
- HOWTO Usage
- Examples
- Example ESP8266_BlynkServoControl
- Debug Terminal Output Samples
- Debug
- Troubleshooting
- Releases
- Issues
- TO DO
- DONE
- Contributions and Thanks
- Contributing
- License
- Copyright
Why do we need this ESP8266_ISR_Servo library
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.
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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.
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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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Avoid using Serial.print()-related functions inside ISR. Just for temporary debug purpose, but even this also can crash the system any time. Beware.
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Your functions are now part of ISR (Interrupt Service Routine), and must be
lean / mean, and follow certain rules. More to read on:
This ESP8266_ISR_Servo library currently supports these following boards:
- ESP8266-based boards.
- Update to match new ESP8266 core v3.0.0
- Fix bug. See Fixed count >= min comparison for servo enable
- Clean-up all compiler warnings possible.
- Add Table of Contents
- Add Version String
- Fix and Optimize old examples
- Add example using Blynk to control servos.
- Change example names to avoid duplication.
- Basic 16 ISR-based servo controllers using 1 hardware timer for ESP8266.
Arduino IDE 1.8.19+for Arduino.
ESP8266 Core 3.0.2+for ESP8266-based boards.
. To use ESP8266 core 2.7.1+ for LittleFS.Blynk_WM library v1.6.2+to use with some examples. To install. check
ESP_DoubleResetDetector library v1.2.1+to use with some examples. To install. check
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:
- Navigate to ESP8266_ISR_Servo page.
- Download the latest release
ESP8266_ISR_Servo-master.zip. - Extract the zip file to
ESP8266_ISR_Servo-masterdirectory - Copy whole
ESP8266_ISR_Servo-masterfolder to Arduino libraries' directory such as~/Arduino/libraries/.
- Install VS Code
- Install PlatformIO
- Install ESP8266_ISR_Servo library by using Library Manager. Search for ESP8266_ISR_Servo in Platform.io Author's Libraries
- 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.
// 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); 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
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); 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); } } - ESP8266_BlynkServoContro
- ESP8266_ISR_MultiServos
- ESP8266_MultipleRandomServos
- ESP8266_MultipleServos
- ISR_MultiServos
- MultipleRandomServos
- MultipleServos
Example ESP8266_BlynkServoControl
1. File ESP8266_BlynkServoControl.ino
// Please use the default Config Portal password MyESP_XXXXXX, where ESP_XXXXXX is the Config Portal SSID #include "defines.h" #include "Credentials.h" #include "dynamicParams.h" //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 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(F("B")); // B means connected to Blynk else Serial.print(F("H")); // H means connected to WiFi but no Blynk } else Serial.print(F("F")); // F means not connected to WiFi and Blynk if (num == 80) { Serial.println(); num = 1; } else if (num++ % 10 == 0) { Serial.print(F(" ")); } } void setup() { // Debug console Serial.begin(115200); while (!Serial); delay(200); #if (USE_LITTLEFS) Serial.print(F("\nStarting ESP8266_BlynkServoControl using LITTLEFS")); #elif (USE_SPIFFS) Serial.print(F("\nStarting ESP8266_BlynkServoControl using SPIFFS")); #else Serial.print(F("\nStarting ESP8266_BlynkServoControl using EEPROM")); #endif #if USE_SSL Serial.print(F(" with SSL on ")); Serial.println(ARDUINO_BOARD); #else Serial.print(F(" without SSL on ")); Serial.println(ARDUINO_BOARD); #endif Serial.println(BLYNK_WM_VERSION); Serial.println(ESP_DOUBLE_RESET_DETECTOR_VERSION); Serial.println(ESP8266_ISR_SERVO_VERSION); Blynk.begin(HOST_NAME); 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(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")); if (servoIndex3 != -1) Serial.println(F("Setup Servo3 OK")); else Serial.println(F("Setup Servo3 failed")); timer.setInterval(30000L, heartBeatPrint); } void loop() { Blynk.run(); timer.run(); }Starting ESP8266_BlynkServoControl using LITTLEFS with SSL on ESP8266_NODEMCU_ESP12E Blynk_WM v1.5.0 ESP_DoubleResetDetector v1.1.1 ESP8266_ISR_Servo v1.2.0 [290] Hostname=8266-Master-Controller [309] LoadCfgFile [309] OK [309] CCSum=0x3817,RCSum=0x3817 [312] LoadCredFile [312] OK [312] CrCCsum=0x2670,CrRCsum=0x2670 [312] Hdr=SSL_ESP8266,BrdName=ESP8266_ISR_Servo [313] SSID=HueNet1,PW=12345678 [316] SSID1=HueNet2,PW1=12345678 [319] Server=account.duckdns.org,Token=token1 [325] Server1=account.duckdns.org,Token1=token2 [331] Port=9443 [333] ======= End Config Data ======= [336] Connecting MultiWifi... [6594] WiFi connected after time: 1 [6594] SSID: HueNet1, RSSI = -36 [6594] Channel: 2, IP address: 192.168.2.166 [6594] bg: WiFi OK. Try Blynk [6596] ___ __ __ / _ )/ /_ _____ / /__ / _ / / // / _ \/ '_/ /____/_/\_, /_//_/_/\_\ /___/ v0.6.1 on ESP8266_NODEMCU_ESP12E [22618] NTP time: Sun Jan 3 07:08:22 2021 [22619] BlynkArduinoClient.connect: Connecting to account.duckdns.org:9443 [23287] Certificate OK [23295] Ready (ping: 2ms). [23366] Connected to Blynk Server = account.duckdns.org, Token = token1 [23366] bg: WiFi+Blynk OK [ISR_SERVO] ESP8266FastTimerInterrupt: _fre = 5000000.00 , _count = 50 [ISR_SERVO] Starting ITimer OK Setup Servo1 OK Setup Servo2 OK Setup Servo3 OK Starting ESP8266_MultipleRandomServos on ESP8266_NODEMCU_ESP12E ESP8266_ISR_Servo v1.2.0 [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 Starting ESP8266_ISR_MultiServos on ESP8266_NODEMCU_ESP12E ESP8266_ISR_Servo v1.2.0 [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 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 1If 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.
- Update to match new ESP8266 core v3.0.0
- Fix bug. See Fixed count >= min comparison for servo enable
- Clean-up all compiler warnings possible.
- Add Table of Contents
- Add Version String
- Fix and Optimize old examples
- Add example using Blynk to control servos.
- Change example names to avoid duplication.
- Basic 16 ISR-based servo controllers using 1 hardware timer for ESP8266.
Submit issues to: ESP8266_ISR_Servo issues
- Search for bug and improvement.
- Similar features for Arduino (UNO, Mega, etc...) and ESP32
- Add functions
getPosition()andgetPulseWidth() - Optimize the code
- Add more complicated examples
- Update to match new ESP8266 core v3.0.0
- 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 |
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