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王立帮
267
arduino-cli/libraries/ESP32_Servo/ESP32_Servo.cpp
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267
arduino-cli/libraries/ESP32_Servo/ESP32_Servo.cpp
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/*
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Copyright (c) 2017 John K. Bennett. All right reserved.
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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* Notes on the implementation:
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* The ESP32 supports 16 hardware LED PWM channels that are intended
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* to be used for LED brightness control. The low level ESP32 code
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* (esp32-hal-ledc.*) allows us to set the PWM frequency and bit-depth,
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* and then manipulate them by setting bits in the relevant control
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* registers.
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*
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* Different servos require different pulse widths to vary servo angle, but the range is
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* an approximately 500-2500 microsecond pulse every 20ms (50Hz). In general, hobbyist servos
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* sweep 180 degrees, so the lowest number in the published range for a particular servo
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* represents an angle of 0 degrees, the middle of the range represents 90 degrees, and the top
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* of the range represents 180 degrees. So for example, if the range is 1000us to 2000us,
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* 1000us would equal an angle of 0, 1500us would equal 90 degrees, and 2000us would equal 180
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* degrees. We vary pulse width (recall that the pulse period is already set to 20ms) as follows:
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*
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* The ESP32 PWM timers allow us to set the timer width (max 20 bits). Thus
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* the timer "tick" length is (pulse_period/2**timer_width), and the equation for pulse_high_width
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* (the portion of the 20ms cycle that the signal is high) becomes:
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*
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* pulse_high_width = count * tick_length
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* = count * (pulse_period/2**timer_width)
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*
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* and count = (pulse_high_width / (pulse_period/2**timer_width))
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*
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* So, for example, if I want a 1500us pulse_high_width, I set pulse_period to 20ms (20000us)
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* (this value is set in the ledcSetup call), and count (used in the ledcWrite call) to
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* 1500/(20000/65536), or 4924. This is the value we write to the timer in the ledcWrite call.
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* If we increase the timer_width, the timer_count values need to be adjusted.
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*
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* The servo signal pins connect to any available GPIO pins on the ESP32, but not all pins are
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* GPIO pins.
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*
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* The ESP32 is a 32 bit processor that includes FP support; this code reflects that fact.
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*/
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#include "ESP32_Servo.h"
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#include "esp32-hal-ledc.h"
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#include "Arduino.h"
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// initialize the class variable ServoCount
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int Servo::ServoCount = 0;
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// The ChannelUsed array elements are 0 if never used, 1 if in use, and -1 if used and disposed
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// (i.e., available for reuse)
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int Servo::ChannelUsed[MAX_SERVOS+1] = {0}; // we ignore the zeroth element
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Servo::Servo()
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{
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this->servoChannel = 0;
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// see if there is a servo channel available for reuse
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bool foundChannelForReuse = false;
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for (int i = 1; i < MAX_SERVOS+1; i++)
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{
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if (ChannelUsed[i] == -1)
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{
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// reclaim this channel
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ChannelUsed[i] = 1;
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this->servoChannel = i;
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foundChannelForReuse = true;
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break;
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}
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}
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if (!foundChannelForReuse)
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{
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// no channels available for reuse; get a new one if we can
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if (ServoCount < MAX_SERVOS)
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{
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this->servoChannel = ++ServoCount; // assign a servo channel number to this instance
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ChannelUsed[this->servoChannel] = 1;
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}
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else
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{
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this->servoChannel = 0; // too many servos in use
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}
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}
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// if we got a channel either way, finish initializing it
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if (this->servoChannel > 0)
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{
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// initialize this channel with plausible values, except pin # (we set pin # when attached)
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this->ticks = DEFAULT_PULSE_WIDTH_TICKS;
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this->timer_width = DEFAULT_TIMER_WIDTH;
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this->pinNumber = -1; // make it clear that we haven't attached a pin to this channel
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this->min = DEFAULT_uS_LOW;
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this->max = DEFAULT_uS_HIGH;
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this->timer_width_ticks = pow(2,this->timer_width);
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}
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}
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int Servo::attach(int pin)
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{
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return (this->attach(pin, DEFAULT_uS_LOW, DEFAULT_uS_HIGH));
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}
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int Servo::attach(int pin, int min, int max)
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{
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if ((this->servoChannel <= MAX_SERVOS) && (this->servoChannel > 0))
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{
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// Recommend only the following pins 2,4,12-19,21-23,25-27,32-33 (enforcement commented out)
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//if ((pin == 2) || (pin ==4) || ((pin >= 12) && (pin <= 19)) || ((pin >= 21) && (pin <= 23)) ||
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// ((pin >= 25) && (pin <= 27)) || (pin == 32) || (pin == 33))
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//{
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// OK to proceed; first check for new/reuse
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if (this->pinNumber < 0) // we are attaching to a new or previously detached pin; we need to initialize/reinitialize
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{
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// claim/reclaim this channel
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ChannelUsed[this->servoChannel] = 1;
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this->ticks = DEFAULT_PULSE_WIDTH_TICKS;
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this->timer_width = DEFAULT_TIMER_WIDTH;
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this->timer_width_ticks = pow(2,this->timer_width);
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}
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this->pinNumber = pin;
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//}
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//else
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//{
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// return 0;
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//}
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// min/max checks
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if (min < MIN_PULSE_WIDTH) // ensure pulse width is valid
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min = MIN_PULSE_WIDTH;
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if (max > MAX_PULSE_WIDTH)
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max = MAX_PULSE_WIDTH;
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this->min = min; //store this value in uS
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this->max = max; //store this value in uS
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// Set up this channel
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// if you want anything other than default timer width, you must call setTimerWidth() before attach
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ledcSetup(this->servoChannel, REFRESH_CPS, this->timer_width); // channel #, 50 Hz, timer width
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ledcAttachPin(this->pinNumber, this->servoChannel); // GPIO pin assigned to channel
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}
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else return 0;
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}
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void Servo::detach()
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{
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if (this->attached())
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{
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ledcDetachPin(this->pinNumber);
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//keep track of detached servos channels so we can reuse them if needed
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ChannelUsed[this->servoChannel] = -1;
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this->pinNumber = -1;
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}
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}
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void Servo::write(int value)
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{
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// treat values less than MIN_PULSE_WIDTH (500) as angles in degrees (valid values in microseconds are handled as microseconds)
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if (value < MIN_PULSE_WIDTH)
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{
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if (value < 0)
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value = 0;
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else if (value > 180)
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value = 180;
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value = map(value, 0, 180, this->min, this->max);
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}
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this->writeMicroseconds(value);
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}
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void Servo::writeMicroseconds(int value)
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{
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// calculate and store the values for the given channel
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if ((this->servoChannel <= MAX_SERVOS) && (this->attached())) // ensure channel is valid
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{
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if (value < this->min) // ensure pulse width is valid
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value = this->min;
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else if (value > this->max)
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value = this->max;
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value = usToTicks(value); // convert to ticks
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this->ticks = value;
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// do the actual write
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ledcWrite(this->servoChannel, this->ticks);
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}
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}
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int Servo::read() // return the value as degrees
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{
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return (map(readMicroseconds()+1, this->min, this->max, 0, 180));
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}
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int Servo::readMicroseconds()
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{
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int pulsewidthUsec;
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if ((this->servoChannel <= MAX_SERVOS) && (this->attached()))
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{
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pulsewidthUsec = ticksToUs(this->ticks);
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}
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else
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{
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pulsewidthUsec = 0;
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}
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return (pulsewidthUsec);
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}
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bool Servo::attached()
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{
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return (ChannelUsed[this->servoChannel]);
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}
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void Servo::setTimerWidth(int value)
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{
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// only allow values between 16 and 20
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if (value < 16)
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value = 16;
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else if (value > 20)
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value = 20;
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// Fix the current ticks value after timer width change
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// The user can reset the tick value with a write() or writeUs()
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int widthDifference = this->timer_width - value;
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// if positive multiply by diff; if neg, divide
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if (widthDifference > 0)
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{
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this->ticks << widthDifference;
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}
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else
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{
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this->ticks >> widthDifference;
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}
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this->timer_width = value;
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this->timer_width_ticks = pow(2,this->timer_width);
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// If this is an attached servo, clean up
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if ((this->servoChannel <= MAX_SERVOS) && (this->attached()))
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{
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// detach, setup and attach again to reflect new timer width
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ledcDetachPin(this->pinNumber);
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ledcSetup(this->servoChannel, REFRESH_CPS, this->timer_width);
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ledcAttachPin(this->pinNumber, this->servoChannel);
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}
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}
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int Servo::readTimerWidth()
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{
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return (this->timer_width);
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}
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int Servo::usToTicks(int usec)
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{
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return (int)((float)usec / ((float)REFRESH_USEC / (float)this->timer_width_ticks));
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}
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int Servo::ticksToUs(int ticks)
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{
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return (int)((float)ticks * ((float)REFRESH_USEC / (float)this->timer_width_ticks));
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}
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