On a Firebeetle ESP32 board, Servo.h can make it impossible to write to Onboard Flash. Reproduce like this:

1. Attach more than 8 servos (I used 9) (in software; hardware doesn't matter)
2. Sometimes required, sometimes not: Output PWM on 9th attached servo using any pin. It is not important what you do with the first 8 servos or if you use them at all.
3. Try to use Preferences.h to write to on-board Flash: Cannot write, and read only returns the default value. No error messages.
4. Detach Servos
5. Try to use Preferences.h again: Works fine

The error occurs irrespective of what pins are used for the Servo. I suspect a problem with timer allocation or something like that, but I am no expert in ESP32 timers or the two libraries involved.

it is useful to detach servo after movement in cases like:

• limit current consumption (servo mechanic could keep position without electronic control for small forces)
• limit servo vibrations (usually present in cheap servos) - sometimes we can observe vibrations after reaching designed position

In current implementation (if I understood correctly) detach() is not controlling pwm state and can disable pwm during high state and move servo to different position.

It would be great to support some safe detach, which will check if pwm is not in active state and won't change servo position.
Proposal for interface:

detach(bool isSafe=false); //false default to keep backward compatibility 
or
safeDetach();

Hello, I found that when I try to use this library with ESP32 Core 3.0, I get errors saying certain functions were not declared in scope (namely ledcSetup, ledcAttachPin, and ledcDetachPin). I found out these functions were removed in Core 3.0 and the same test sketch I use works perfectly with Core 2.0.17.

If you are having trouble try going to the board manager and changing your esp32 installation to 2.0.17

Change category to "Device control"?

Hi, I am trying to use this library on ESP32, but when I try to build the example I get more errors:

for example:
In file included from src/main.cpp:2: .pio/libdeps/esp32dev/ServoESP32/src/Servo.h:68:81: error: call to non-'constexpr' function 'const _Tp& std::min(const _Tp&, const _Tp&) [with _Tp = int]' static const int TIMER_RESOLUTION = std::min(16, SOC_LEDC_TIMER_BIT_WIDE_NUM);

Log, platformio.ini and code included.

Platform versions:
Espressif32 6.4.0
Atmel AVR 4.2.0

attachments.zip

When you write it like "#include <Servo.h>", it conflicts with the other library, so ı can't load the code on my esp32.

Unfortunately, I am unable to control a servo on the Seeed Studio XIAO ESP32C3.

Is it possible to have some compile-time check of the attach() parameters, e.g. with constexp?

https://github.com/RoboticsBrno/ESP32-Arduino-Servo-Library/blob/4b1f4a560bc0e25c51faf7ac7a7fc35773a4ba7c/src/Servo.cpp#L60

I am now thinking about modification like this:

    _minAngle = constrain(minAngle, MIN_ANGLE, MAX_ANGLE);
    _maxAngle = constrain(maxAngle, MIN_ANGLE, MAX_ANGLE);
    _minPulseWidth = constrain(minPulseWidth, MIN_PULSE_WIDTH, MAX_PULSE_WIDTH);
    _maxPulseWidth = constrain(maxPulseWidth, MIN_PULSE_WIDTH, MAX_PULSE_WIDTH);

But that is a hidden side effect and I would like rather make the check in the compile-time and show same compile message (if the parameters would be constexp). Is that possible @yaqwsx ?

Or is there some better way? Are exceptions available in the Arduino EPS32 framework or how the ESP-IDF throws the error message?

When compiling for the DOIT ESP32 DEVKIT V1 board on Arduino IDE 1.8.10 I am getting conflicts with the "default" Arduino servo library.

Due to this problem, none of the examples compiles.

This is easily fixed by changing the name of the header file to something more unique. Ideally, Arduino IDE would have a way of differentiating them, but yeah, it doesn't.

I suggest by renaming Servo.h ➡️ ESP32ArduinoServo.h. Based on the name you have chosen for your repository, this sounds like a reasonable choice to me.

#10 should solve this issue.

Hi and thanks for this library.

It seems like the frequency parameter that can be passed to the attach function is not actually changing the frequency but the pulse width.
I have initialized two Servos like this:

  myservo1.attach(servoPin1, Servo::CHANNEL_NOT_ATTACHED, Servo::DEFAULT_MIN_ANGLE,
            Servo::DEFAULT_MAX_ANGLE, Servo::DEFAULT_MIN_PULSE_WIDTH_US,
            Servo::DEFAULT_MAX_PULSE_WIDTH_US, 200);

  myservo2.attach(servoPin2);

Here are signals measured on two pins, the first (yellow) one was set at 200Hz, and the second (blue) one was left at default value which is 50Hz
And both signals are actually at 50Hz

Here is what is expected: the yellow signal has a frequency 4 times higher:

The channel allocation mechanism in this library is primitive and buggy. As a result, if you use the automatic channel allocation feature, repeated calls to detach and attach will cause the library to exhaust the supply of channels and it will stop functioning.

I have worked around this by avoiding the automatic allocation and instead passing servo-specific channel references in the call to attach. However, this bug can be easily fixed as follows:

Instead of treating the "channel_next_free" static integer as single channel number, treat it as a bitfield. Then, when allocating a channel in attach(), set the bit associated with that channel to mark it as in use. Finally, clear said bit in the detach() function.

In other words in the implementation of attach() replace this code:

    if(channel == CHANNEL_NOT_ATTACHED) {
        if(channel_next_free == CHANNEL_MAX_NUM) {
            return false;
        }
        _channel = channel_next_free;
        channel_next_free++;
    } else {
        _channel = channel;
    }

with this:

    if(channel == CHANNEL_NOT_ATTACHED) {
        for (int mask = 1; mask != 0; mask <<= 1)  {
            ++channel;
            if((channel_next_free & mask) == 0) {
                break;
            }
        }
    }
    if(channel > CHANNEL_NOT_ATTACHED && channel < CHANNEL_MAX_NUM) {
        _channel = channel;
        channel_next_free |= (1 << channel);
    } else {
        return false;
    }

and in the implementation of detach() replace this code:

    if(_channel == (channel_next_free - 1))
        channel_next_free--;

with this:

    channel_next_free &= ~(1 << _channel);

I use this lib in PlatformIO for CLion, but the console print these msgs shown in the img after PlatformIO build.

So I clone this repository, and also can not find the methods was not declared.

Thanks for this library, first of all! I am using it to flip the light switch in my workshop after receiving a command over MQTT. Works nicely!

I was looking into testing my code a bit more and wanted to fake (mock) the real servos in my test code. I found ArdiunoFake, which is based on FakeIt. Both are focused on providing mocks of interfaces, which is hard (impossible?) to do with concrete classes like Servo.

Looking at the code, it seems quite possible to rename the current Servo class to e.g. ServoESP32 and then extract a new Servo interface from it. Doing this would make mocking and testing the code using Servo possible or at least much easier.

The downside would that it breaks backward compatibility. If that is an issue, keeping Servo and extracting IServo would be a possibility (not preferred by me, at least).

Before investing time into that, I wanted to check if there is interest in a contribution like this, or if there are alternative suggestions how to unit-test code that is using this library without having to attach an actual servo during testing.

Hi,
First of all thanks for your code.
I am starting with ESP32 and I did a small snippet to control a servo with a webpage. All works good but I add an api route to the server to read the position of the servo, and there is always a difference of 1 degree. I do for example myServo.write(90), and when I do myServo.read() I get 89, is this normal? is because of my servo?
I am using one old hitec HS-300

Thanks!

https://github.com/RoboticsBrno/ESP32-Arduino-Servo-Library/blob/4b1f4a560bc0e25c51faf7ac7a7fc35773a4ba7c/src/Servo.cpp#L60

Set up a GitHub Action for building the examples in Arduino IDE and PlatformIO environment.

Not very good implementation of the selecting and releasing the channels for the ledcSetup() function:
https://github.com/RoboticsBrno/ESP32-Arduino-Servo-Library/blob/master/src/Servo.cpp#L49

Tip: implement by std:bitset to remember used channels.

hi
this servo (SUMO 1143HB) has a mechanical 360 degree rotation.
I'm testing this servo on ESP32 and using this library is not possible to obtain more than 180 degree rotation.
For my use I need a 260 degree rotation
I tried to modify the .h and .cpp but i'm not smart in c++, so at moment i found no solution.
someone may help me to do this ?
I saw a lot of video but all them make a hardware modification.
I'm sure that with this kind of servo is possible to obtain 260 degree via software too.
Please look the video that solve the problem without opening of servo
https://www.aliexpress.com/item/1005002973104855.html?spm=a2g0o.order_list.order_list_main.19.21ef1802XnKwfL

your help is appreciated

Hi, fist of all, thx for your lib!

I can't build my sketch because of these errors, I'm using PlatformIO, but I've tested ArduinoIDE and received diferent erro on the same file and line of code:

PlatformIO
Executing task in folder Nykko_Brat_rsuzano: platformio run --target upload

Processing esp32dev (platform: espressif32; board: esp32dev; framework: arduino)

Verbose mode can be enabled via -v, --verbose option
CONFIGURATION: https://docs.platformio.org/page/boards/espressif32/esp32dev.html
PLATFORM: Espressif 32 (5.2.0) > Espressif ESP32 Dev Module
HARDWARE: ESP32 240MHz, 320KB RAM, 4MB Flash
DEBUG: Current (cmsis-dap) External (cmsis-dap, esp-bridge, esp-prog, iot-bus-jtag, jlink, minimodule, olimex-arm-usb-ocd, olimex-arm-usb-ocd-h, olimex-arm-usb-tiny-h, olimex-jtag-tiny, tumpa)
PACKAGES:

• framework-arduinoespressif32 @ 3.20005.220925 (2.0.5)
• tool-esptoolpy @ 1.40201.0 (4.2.1)
• tool-mkfatfs @ 2.0.1
• tool-mklittlefs @ 1.203.210628 (2.3)
• tool-mkspiffs @ 2.230.0 (2.30)
• toolchain-xtensa-esp32 @ 8.4.0+2021r2-patch3
  LDF: Library Dependency Finder -> https://bit.ly/configure-pio-ldf
  LDF Modes: Finder ~ chain, Compatibility ~ soft
  Found 37 compatible libraries
  Scanning dependencies...
  Dependency Graph
  |-- DabbleESP32 @ 1.5.1
  |-- PWMMotorControl @ 2.1.0
  |-- ESP32 AnalogWrite @ 0.2.0
  |-- ServoESP32 @ 1.1.1
  |-- Preferences @ 2.0.0
  Building in release mode
  Compiling .pio/build/esp32dev/src/main.cpp.o
  In file included from src/main.h:5,
  from src/main.cpp:1:
  .pio/libdeps/esp32dev/ServoESP32/src/Servo.h:68:81: error: call to non-'constexpr' function 'const _Tp& std::min(const _Tp&, const _Tp&) [with _Tp = int]'
  static const int TIMER_RESOLUTION = std::min(16, SOC_LEDC_TIMER_BIT_WIDE_NUM);
  ^
  .pio/libdeps/esp32dev/ServoESP32/src/Servo.h: In member function 'T ServoTemplate::mapTemplate(T, T, T, T, T) const':
  .pio/libdeps/esp32dev/ServoESP32/src/Servo.h:256:12: warning: 'if constexpr' only available with -std=c++17 or -std=gnu++17
  if constexpr (std::is_floating_point_v) {
  ^~~~~~~~~
  .pio/libdeps/esp32dev/ServoESP32/src/Servo.h:256:28: error: 'is_floating_point_v' is not a member of 'std'
  if constexpr (std::is_floating_point_v) {
  ^~~~~~~~~~~~~~~~~~~
  .pio/libdeps/esp32dev/ServoESP32/src/Servo.h:256:28: note: suggested alternative: 'is_floating_point'
  if constexpr (std::is_floating_point_v) {
  ^~~~~~~~~~~~~~~~~~~
  is_floating_point
  .pio/libdeps/esp32dev/ServoESP32/src/Servo.h:256:49: error: expected primary-expression before '>' token
  if constexpr (std::is_floating_point_v) {
  ^
  .pio/libdeps/esp32dev/ServoESP32/src/Servo.h:256:50: error: expected primary-expression before ')' token
  if constexpr (std::is_floating_point_v) {
  ^
  .pio/libdeps/esp32dev/ServoESP32/src/Servo.h: In member function 'T ServoTemplate::mapTemplate(T, T, T, T, T) const [with T = int]':
  .pio/libdeps/esp32dev/ServoESP32/src/Servo.h:262:5: warning: control reaches end of non-void function [-Wreturn-type]

ArduinoIDE
In file included from /home/rsuzano/Arduino/libraries/ServoESP32/examples/01-SimpleServo/01-SimpleServo.ino:1:0:
/home/rsuzano/Arduino/libraries/ServoESP32/src/Servo.h:68:54: error: 'SOC_LEDC_TIMER_BIT_WIDE_NUM' was not declared in this scope
static const int TIMER_RESOLUTION = std::min(16, SOC_LEDC_TIMER_BIT_WIDE_NUM);
^
/home/rsuzano/Arduino/libraries/ServoESP32/src/Servo.h: In member function 'bool ServoTemplate::attach(int, int, T, T, int, int, int)':
/home/rsuzano/Arduino/libraries/ServoESP32/src/Servo.h:52:24: error: 'SOC_LEDC_CHANNEL_NUM' was not declared in this scope
#define LEDC_CHANNELS (SOC_LEDC_CHANNEL_NUM)
^
/home/rsuzano/Arduino/libraries/ServoESP32/src/Servo.h:132:38: note: in expansion of macro 'LEDC_CHANNELS'
if (channel_next_free == LEDC_CHANNELS) {
^
/home/rsuzano/Arduino/libraries/ServoESP32/src/Servo.h: In member function 'T ServoTemplate::mapTemplate(T, T, T, T, T) const':
/home/rsuzano/Arduino/libraries/ServoESP32/src/Servo.h:256:12: error: expected '(' before 'constexpr'
if constexpr (std::is_floating_point_v) {
^
/home/rsuzano/Arduino/libraries/ServoESP32/src/Servo.h:258:11: error: 'else' without a previous 'if'
} else {

This library changes the order of parameters in the attach() function as compared to the standard arduino library, please change this or document it!
Thanks

The link to platformio page need to changed to https
http will 404
https://platformio.org/lib/show/1739/ServoESP32

error: 'ledcRead' was not declared in this scope

This library works perfectly with regular servos, like SG90, but when I tried high torque MG996R, behavior is stochastic. I know, MG996R is continuous servo but motor don't want "behave" even as described here (in answer).

Any suggestions guys? Or please share a link to the standard high torque servos, not expensive as a hell 😉

Hello, thank you for developing this library. I am using the ESP32-S2 and from expressif's documentation, the PWM's are limited to 14-bits. As written, I have not been able to get the code to work on an S2, however, once I changed the ledcSetup call to 14, it works well.

From:
ledcSetup(_channel, 50, 16); // channel X, 50 Hz, 16-bit depth

To:
ledcSetup(_channel, 50, 14); // channel X, 50 Hz, 14-bit depth

You may want to consider with passing this as a variable or creating a function that allows this to be set. Thanks again.