/** * Copyright (c) 2020 Raspberry Pi (Trading) Ltd. * * SPDX-License-Identifier: BSD-3-Clause */ // Fade an LED between low and high brightness. An interrupt handler updates // the PWM slice's output level each time the counter wraps. #include "pico/stdlib.h" #include <stdio.h> #include "pico/time.h" #include "hardware/irq.h" #include "hardware/pwm.h" #ifdef PICO_DEFAULT_LED_PIN void on_pwm_wrap() { static int fade = 0; static bool going_up = true; // Clear the interrupt flag that brought us here pwm_clear_irq(pwm_gpio_to_slice_num(PICO_DEFAULT_LED_PIN)); if (going_up) { ++fade; if (fade > 255) { fade = 255; going_up = false; } } else { --fade; if (fade < 0) { fade = 0; going_up = true; } } // Square the fade value to make the LED's brightness appear more linear // Note this range matches with the wrap value pwm_set_gpio_level(PICO_DEFAULT_LED_PIN, fade * fade); } #endif int main() { #ifndef PICO_DEFAULT_LED_PIN #warning pwm/led_fade example requires a board with a regular LED #else // Tell the LED pin that the PWM is in charge of its value. gpio_set_function(PICO_DEFAULT_LED_PIN, GPIO_FUNC_PWM); // Figure out which slice we just connected to the LED pin uint slice_num = pwm_gpio_to_slice_num(PICO_DEFAULT_LED_PIN); // Mask our slice's IRQ output into the PWM block's single interrupt line, // and register our interrupt handler pwm_clear_irq(slice_num); pwm_set_irq_enabled(slice_num, true); irq_set_exclusive_handler(PWM_DEFAULT_IRQ_NUM(), on_pwm_wrap); irq_set_enabled(PWM_DEFAULT_IRQ_NUM(), true); // Get some sensible defaults for the slice configuration. By default, the // counter is allowed to wrap over its maximum range (0 to 2**16-1) pwm_config config = pwm_get_default_config(); // Set divider, reduces counter clock to sysclock/this value pwm_config_set_clkdiv(&config, 4.f); // Load the configuration into our PWM slice, and set it running. pwm_init(slice_num, &config, true); // Everything after this point happens in the PWM interrupt handler, so we // can twiddle our thumbs while (1) tight_loop_contents(); #endif }

This firmware image was imported from the pico-examples repository. 


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