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89 lines
3.3 KiB
C
89 lines
3.3 KiB
C
/**
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* @file servo.c
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* @brief Implementation of a simple SG90 servo driver using PWM (50Hz)
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* @author Kevin Thomas
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* @date 2025
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*
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* MIT License
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*
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* Copyright (c) 2025 Kevin Thomas
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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#include "servo.h"
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#include "pico/stdlib.h"
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#include "hardware/pwm.h"
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#include "hardware/clocks.h"
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// Default servo pulse range (SG90 typical)
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static const uint16_t SERVO_DEFAULT_MIN_US = 1000;
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static const uint16_t SERVO_DEFAULT_MAX_US = 2000;
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// internal state
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static uint8_t servo_pin = 0;
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static uint servo_slice = 0;
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static uint servo_chan = 0;
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static uint32_t servo_wrap = 20000 - 1; // wrap to map microseconds for 50Hz
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static float servo_hz = 50.0f;
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// Convert microsecond pulse to PWM level based on wrap and frequency
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static uint32_t pulse_us_to_level(uint32_t pulse_us) {
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const float period_us = 1000000.0f / servo_hz; // 20000us
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float counts_per_us = (servo_wrap + 1) / period_us;
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return (uint32_t)(pulse_us * counts_per_us + 0.5f);
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}
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void servo_init(uint8_t pin) {
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servo_pin = pin;
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// Configure GPIO for PWM
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gpio_set_function(servo_pin, GPIO_FUNC_PWM);
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servo_slice = pwm_gpio_to_slice_num(servo_pin);
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servo_chan = pwm_gpio_to_channel(servo_pin);
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pwm_config config = pwm_get_default_config();
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// Calculate clock divider to achieve 50 Hz with our chosen wrap
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const uint32_t sys_clock_hz = clock_get_hz(clk_sys);
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float clock_div = (float)sys_clock_hz / (servo_hz * (servo_wrap + 1));
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pwm_config_set_clkdiv(&config, clock_div);
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pwm_config_set_wrap(&config, servo_wrap);
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pwm_init(servo_slice, &config, true);
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}
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void servo_set_pulse_us(uint16_t pulse_us) {
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if (servo_pin == 0) return; // not initialized
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// clamp to defaults
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if (pulse_us < SERVO_DEFAULT_MIN_US) pulse_us = SERVO_DEFAULT_MIN_US;
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if (pulse_us > SERVO_DEFAULT_MAX_US) pulse_us = SERVO_DEFAULT_MAX_US;
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uint32_t level = pulse_us_to_level(pulse_us);
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pwm_set_chan_level(servo_slice, servo_chan, level);
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}
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void servo_set_angle(float degrees) {
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if (degrees < 0.0f) degrees = 0.0f;
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if (degrees > 180.0f) degrees = 180.0f;
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// linear map 0..180 -> min_us..max_us
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float ratio = degrees / 180.0f;
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uint16_t pulse = (uint16_t)(SERVO_DEFAULT_MIN_US + ratio * (SERVO_DEFAULT_MAX_US - SERVO_DEFAULT_MIN_US) + 0.5f);
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servo_set_pulse_us(pulse);
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}
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# |