ESP32_C3_ISR_Servo Library

ESP32_C3_ISR_Servo libraryGitHub release

Why do we need this ESP32_C3_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 ESP32_C3-based board to control up to 16 independent servo motors.

Currently supported Boards

  1. ESP32_C3-based boards, such as ESP32C3_DEV, etc

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.


Releases v1.1.0

  1. Basic 16 ISR-based servo controllers using 1 hardware timer for ESP32_C3.
  2. Tested with ESP32 core v2.0.0-rc1 and v1.0.6


  1. ESP32_C3_ISR_MultiServos
  2. ESP32_C3_MultipleRandomServos
  3. ESP32_C3_MultipleServos
  4. ISR_MultiServos
  5. MultipleRandomServos
  6. MultipleServos

Example ESP32_C3_ISR_MultiServos on ESP32C3_DEV

The following is the sample terminal output when running example ESP32_C3_ISR_MultiServos to demonstrate how to control multiple Servos using 1 hardware timer.

Starting ESP32_C3_ISR_MultiServos on ESP32C3_DEV
ESP32_C3_ISR_Servo v1.1.0
[ISR_SERVO] ESP32_C3_FastTimerInterrupt: _timerNo = 3 , _fre = 1000000
[ISR_SERVO] Starting  ITimer OK
Setup Servo1 OK
Setup Servo2 OK
Servo1 pos = 0, Servo2 pos = 180
Servo1 pos = 30, Servo2 pos = 150
Servo1 pos = 60, Servo2 pos = 120
Servo1 pos = 90, Servo2 pos = 90
Servo1 pos = 120, Servo2 pos = 60
Servo1 pos = 150, Servo2 pos = 30
Servo1 pos = 180, Servo2 pos = 0

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