timer_lowlevel.c (timer_lowlevel sample)

/** * Copyright (c) 2020 Raspberry Pi (Trading) Ltd. * * SPDX-License-Identifier: BSD-3-Clause */ #include <stdio.h> #include "pico/stdlib.h" #include "hardware/timer.h" #include "hardware/irq.h" // Note on RP2350 timer_hw is the default timer instance (as per PICO_DEFAULT_TIMER) /// \tag::get_time[] // Simplest form of getting 64 bit time from the timer. // It isn't safe when called from 2 cores because of the latching // so isn't implemented this way in the sdk static uint64_t get_time(void) { // Reading low latches the high value uint32_t lo = timer_hw->timelr; uint32_t hi = timer_hw->timehr; return ((uint64_t) hi << 32u) | lo; } /// \end::get_time[] /// \tag::alarm_standalone[] // Use alarm 0 #define ALARM_NUM 0 #define ALARM_IRQ hardware_alarm_get_irq_num(timer_hw, ALARM_NUM) // Alarm interrupt handler static volatile bool alarm_fired; static void alarm_irq(void) { // Clear the alarm irq hw_clear_bits(&timer_hw->intr, 1u << ALARM_NUM); // Assume alarm 0 has fired printf("Alarm IRQ fired\n"); alarm_fired = true; } static void alarm_in_us(uint32_t delay_us) { // Enable the interrupt for our alarm (the timer outputs 4 alarm irqs) hw_set_bits(&timer_hw->inte, 1u << ALARM_NUM); // Set irq handler for alarm irq irq_set_exclusive_handler(ALARM_IRQ, alarm_irq); // Enable the alarm irq irq_set_enabled(ALARM_IRQ, true); // Enable interrupt in block and at processor // Alarm is only 32 bits so if trying to delay more // than that need to be careful and keep track of the upper // bits uint64_t target = timer_hw->timerawl + delay_us; // Write the lower 32 bits of the target time to the alarm which // will arm it timer_hw->alarm[ALARM_NUM] = (uint32_t) target; } int main() { stdio_init_all(); printf("Timer lowlevel!\n"); // Set alarm every 2 seconds while (1) { alarm_fired = false; alarm_in_us(1000000 * 2); // Wait for alarm to fire while (!alarm_fired); } } /// \end::alarm_standalone[]