Servo Library for ESP32

This library attempts to faithfully replicate the semantics of the Arduino Servo library (see http://www.arduino.cc/en/Reference/Servo) for the ESP32, with two (optional) additions. The two new functions expose the ability of the ESP32 PWM timers to vary timer width.

License

Copyright (c) 2017 John K. Bennett. All right reserved.

This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA

Library Description:

Servo - Class for manipulating servo motors connected to ESP32 pins.
int attach(pin )  - Attaches the given GPIO pin to the next free channel
    (channels that have previously been detached are used first),
    returns channel number or 0 if failure. All pin numbers are allowed,
    but only pins 2,4,12-19,21-23,25-27,32-33 are recommended.
int attach(pin, min, max  ) - Attaches to a pin setting min and max
    values in microseconds; enforced minimum min is 500, enforced max
    is 2500. Other semantics are the same as attach().
void write () - Sets the servo angle in degrees; a value below 500 is
    treated as a value in degrees (0 to 180). These limit are enforced,
    i.e., values are constrained as follows:
        Value                                   Becomes
        -----                                   -------
        < 0                                        0
        0 - 180                                 value (treated as degrees)
        181 - 499                                 180
        500 - (min-1)                             min
        min-max (from attach or default)   value (treated as microseconds)
        (max+1) - 2500                            max

void writeMicroseconds() - Sets the servo pulse width in microseconds.
    min and max are enforced (see above).
int read() - Gets the last written servo pulse width as an angle between 0 and 180.
int readMicroseconds()   - Gets the last written servo pulse width in microseconds.
bool attached() - Returns true if this servo instance is attached to a pin.
void detach() - Stops an the attached servo, frees the attached pin, and frees
    its channel for reuse.

• New ESP32-specific functions ** setTimerWidth(value) - Sets the PWM timer width (must be 16-20) (ESP32 ONLY); as a side effect, the pulse width is recomputed. int readTimerWidth() - Gets the PWM timer width (ESP32 ONLY)

Useful Defaults:

default min pulse width for attach(): 1000us default max pulse width for attach(): 2000us default timer width 16 (if timer width is not set) default pulse width 1500us (servos are initialized with this value) MINIMUM pulse with: 500us MAXIMUM pulse with: 2500us MAXIMUM number of servos: 16 (this is the number of PWM channels in the ESP32)