Some key RP2040 code points I thought I'd explain

Some stuff I don't think the RP2040 SDK documentation explains super well https://www.raspberrypi.com/documentation/pico-sdk/

Simple Timers

Vars & Refs

alarm_pool_t *ack_alarm_pool;
alarm_id_t ack_alarm_id;
static int64_t ack_timer_callback(alarm_id_t id, void *user_data);

Create a new alarm pool to use

ack_alarm_pool = alarm_pool_create_with_unused_hardware_alarm(4);

Set an alarm to run ack_timer_callback() in 1000 milliseconds

ack_alarm_id = alarm_pool_add_alarm_in_ms(ack_alarm_pool, 1000, ack_timer_callback, NULL, true);

Timer callback function example

static int64_t ack_timer_callback(alarm_id_t id, void *user_data) {
    send_ack = true;
    return 0;  // don't repeat
}