PServo

An Arduino library designed to make working with multiple servo motors simpler and more intuitive, especially for those building complex robots. With PServo, you can easily control the movements of multiple servos at the same time and even create more advanced motion sequences. The library introduces a design pattern that I call Scene-Oriented Programming, making it easier to choreograph and synchronize servo movements for your projects.

PServo demo

Installation

PServo is built as a state machine, so it requires the Servo.h library to function properly. Make sure you have that installed as well.

Option 1: Manual Installation

• Visit the releases page on GitHub.
• Download the .zip file for the version you want.
• Extract the .zip file into your Arduino libraries folder:
  • On Linux or Mac: ~/Arduino/libraries
  • On Windows: Documents\Arduino\libraries

Option 2: Using Arduino CLI (Recommended)

If you prefer a faser method, you can use the following Arduino CLI command:

arduino-cli lib install --git-url https://github.com/kevinmarquesp/PServo

‍[!NOTE] If you haven’t configured the Arduino CLI to allow unsafe library installations, you might need to follow this documentation to enable it. In short, run arduino-cli config init, open the generated file, and set library.enable_unsafe_install to true. That’s it!

Usage

This library doesn’t use the delay() function to control the speed of movements, as it would pause the entire program, which isn’t suitable for most Arduino applications. Instead, it relies on the millis() function to determine when to wait and when to execute movements, similar to other Arduino projects.

The general structure of your application should look something like this:

unsigned long timer = 0;
 
void setup(void) {
  // ...rest of the code...
}
 
void loop(void) {
  timer = millis();
 
  // ...rest of the code...
}

First, import the Servo.h and PServo.h libraries, then create the servo objects you want to control, along with a PServo object for each servo. The PServo object will calculate the servo position, and you'll need to update the actual servo object with these calculated values.

#include <Servo.h>
#include <PServo.h>
 
unsigned long timer = 0;
 
Servo servo_right;
Servo servo_left;
 
PServo machine_right(&timer, 0, 180, true);
PServo machine_left(&timer, 0, 180, true);
 
void setup(void) {
  servo_right.attach(7);
  servo_left.attach(6);
}

‍In this example, the line PServo machine_left(&timer, 0, 180, true); initializes a PServo object with a minimum value of 0, a maximum value of 180, and the true parameter indicates that this machine allows looping. When the movement sequence ends, it will automatically restart.

Since the timer pointer lets the PServo object track the current time in your application, you'll need to update the servo positions within the loop() function. The process involves getting the current position from each PServo object and then writing that position to the corresponding servo object:

void loop(void) {
    timer = millis();
 
    servo_right.write(machine_right.get_pos());
    servo_left.write(machine_left.get_pos());
 
    // ...rest of the code...
}

To configure the moveset for the servos, start with the .begin() method, followed by a series of move() calls. The .begin() method indicates the start of a new movement sequence, while each move() method specifies a movement to be performed. The PServo object will manage which movement is currently active and which should be skipped. It’s important to define this moveset within the loop() function:

void loop(void) {
    // ...rest of the code...
 
    machine_right.begin();
    machine_right.move(180, 15);  // Go to 180º waiting 15 ms for each deg update.
    machine_right.move(0, 20);    // Go to 0º waiting 0 ms for each deg update.
 
    machine_left.begin();
    machine_left.move(180, 20);
    machine_left.move(0, 0);
}

Since repeatedly writing the machine name can be tedious, this library provides a syntax shortcut to simplify your code. The following code does the same as the one above:

void loop(void) {
    // ...rest of the code...
 
    machine_right.begin()
        ->move(180, 15)
        ->move(0, 20);
 
    machine_left.begin()
        ->move(180, 20)
        ->move(0, 0);
}

This is just a basic example. For more details on what this library can do and how to implement additional features, check out the official documentation and the example sketches to learn more.

Contributing

If you’d like to contribute to the development of PServo, follow these steps:

Getting Started

1. Clone the repository:

git clone https://github.com/kevinmarquesp/PServo
cd PServo

1. Set up dependencies:

make deps # Clone and/or build vendorized libraries.

Testing (Arduino Board not Required)

You can run tests without needing an Arduino board.

Run All Tests

To run the entire test suite:

make deps
make test

Run a Specific Test

To run a specific test, specify the test file with the GTEST_UNITS variable:

make deps
make test GTEST_UNITS=extra/gtest/test_gtest.cpp