/** * Copyright (c) 2020 Raspberry Pi (Trading) Ltd. * * SPDX-License-Identifier: BSD-3-Clause */ #include <stdio.h> #include "pico/stdlib.h" #include "pico/util/queue.h" bool timer_callback(repeating_timer_t *rt); queue_t sample_fifo; // using struct as an example, but primitive types can be used too typedef struct element { uint value; } element_t; const int FIFO_LENGTH = 32; int main() { stdio_init_all(); int hz = 25; queue_init(&sample_fifo, sizeof(element_t), FIFO_LENGTH); repeating_timer_t timer; // negative timeout means exact delay (rather than delay between callbacks) if (!add_repeating_timer_us(-1000000 / hz, timer_callback, NULL, &timer)) { printf("Failed to add timer\n"); return 1; } // read some blocking for (int i = 0; i < 10; i++) { element_t element; queue_remove_blocking(&sample_fifo, &element); printf("Got %d: %d\n", i, element.value); } // now retrieve all that are available periodically (simulate polling) for (int i = 0; i < 10; i++) { int count = queue_get_level(&sample_fifo); if (count) { printf("Getting %d, %d:\n", i, count); for (; count > 0; count--) { element_t element; queue_remove_blocking(&sample_fifo, &element); printf(" got %d\n", element.value); } } sleep_us(5000000 / hz); // sleep for 5 times the sampling period } cancel_repeating_timer(&timer); // drain any remaining element_t element; while (queue_try_remove(&sample_fifo, &element)) { printf("Got remaining %d\n", element.value); } queue_free(&sample_fifo); printf("Done\n"); return 0; } bool timer_callback(__unused repeating_timer_t *rt) { static int v = 100; element_t element = { .value = v }; v += 100; if (!queue_try_add(&sample_fifo, &element)) { printf("FIFO was full\n"); } return true; // keep repeating }

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


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