raspberrypi-utils-sys 0.0.4

Low-level unsafe bindings to raspberrypi-utils
Documentation 
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/**
 * Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

#include <stdio.h>
#include <stdlib.h>

#include "pico/stdlib.h"
#include "hardware/pio.h"
#include "pwm.pio.h"

// Write `period` to the input shift register
void pio_pwm_set_period(PIO pio, uint sm, uint32_t period) {
    pio_sm_set_enabled(pio, sm, false);
    pio_sm_put_blocking(pio, sm, period);
    pio_sm_exec(pio, sm, pio_encode_pull(false, false));
    pio_sm_exec(pio, sm, pio_encode_out(pio_isr, 32));
    pio_sm_set_enabled(pio, sm, true);
}

// Write `level` to TX FIFO. State machine will copy this into X.
void pio_pwm_set_level(PIO pio, uint sm, uint32_t level) {
    pio_sm_put_blocking(pio, sm, level);
}

int main(int argc, const char **argv) {
    stdio_init_all();

    PIO pio = pio0;
    int sm = pio_claim_unused_sm(pio, true);
    uint offset = pio_add_program(pio, &pwm_program);
    uint gpio = 4;
    if (argc == 2)
        gpio = (uint)strtoul(argv[1], NULL, 0);
    printf("Loaded program at %d, using sm %d, gpio %d\n", offset, sm, gpio);

    pwm_program_init(pio, sm, offset, gpio);
    pio_pwm_set_period(pio, sm, (1u << 16) - 1);

    int level = 0;
    while (true) {
        //printf("Level = %d\n", level);
        pio_pwm_set_level(pio, sm, level * level);
        level = (level + 1) % 256;
        sleep_ms(50);
    }
}