How to count milliseconds on the Raspberry Pi Pico? - c++

Question

I want to count milliseconds on my Pico to make nonblocking code in C++.
Arduino has the millis() function, but after looking though all the example programs and scouring the internet I couldn't find anything like that for the Pico using C++.
This is the BlinkWithoutDelay sketch from the Arduino examples that shows what I want to do:
const int ledPin = LED_BUILTIN;// the number of the LED pin
// Variables will change:
int ledState = LOW; // ledState used to set the LED
// Generally, you should use "unsigned long" for variables that hold time
// The value will quickly become too large for an int to store
unsigned long previousMillis = 0; // will store last time LED was updated
// constants won't change:
const long interval = 1000; // interval at which to blink (milliseconds)
void setup() {
// set the digital pin as output:
pinMode(ledPin, OUTPUT);
}
void loop() {
// here is where you'd put code that needs to be running all the time.
// check to see if it's time to blink the LED; that is, if the difference
// between the current time and last time you blinked the LED is bigger than
// the interval at which you want to blink the LED.
unsigned long currentMillis = millis();
if (currentMillis - previousMillis >= interval) {
// save the last time you blinked the LED
previousMillis = currentMillis;
// if the LED is off turn it on and vice-versa:
if (ledState == LOW) {
ledState = HIGH;
} else {
ledState = LOW;
}
// set the LED with the ledState of the variable:
digitalWrite(ledPin, ledState);
}
}

Answer 1

I decided to go with a repeating timer as suggested by some comments and the examples that used it really difficult to understand for me. So I'll try to explain it the best I can.
*Note that I don't really understand some of the values being passed into functions but I know enough to make this work. Please feel free to correct me
#include "pico/stdlib.h"
bool led_state;
//Function Called by the timer
bool timer_callback( repeating_timer_t *rt )
{
//Blinks the LED
led_state = !led_state;
gpio_put(25, led_state);
return (true);
}
int main(){
//From what I can tell this creates an identifier for the timer
static repeating_timer_t timer;
stdio_init_all();
//GPIO setting (GPIO_25 is the LED pin on the pico)
gpio_init(25);
gpio_set_dir(25, GPIO_OUT);
//Sets a repeating timer to call a function every 1000 milliseconds
//add_repeating_timer_ms( int interval_in_milliseconds, ?&function to call?, ???, ?timer identifier? );
add_repeating_timer_ms( 1000, &timer_callback, NULL, &timer );
while(true){
//Blinks LED briefly at a different interval than the repeating timer
//This is to show that my code isn't blocked
gpio_put(25, !led_state);
sleep_ms(50);
gpio_put(25, led_state);
sleep_ms(450);
}
return 0;
}