Datasheet

4.6.4.3. Busy wait
If you don’t want to use an alarm to wait for a period of time, instead use a while loop. The SDK provides various
busy_wait_ functions to do this:
SDK: https://github.com/raspberrypi/pico-sdk/tree/master/src/rp2_common/hardware_timer/timer.c Lines 57 - 102
Ê57 void busy_wait_us_32(uint32_t delay_us) {
Ê58 if (0 <= (int32_t)delay_us) {
Ê59 // we only allow 31 bits, otherwise we could have a race in the loop below with
Ê60 // values very close to 2^32
Ê61 uint32_t start = timer_hw->timerawl;
Ê62 while (timer_hw->timerawl - start < delay_us) {
Ê63 tight_loop_contents();
Ê64 }
Ê65 } else {
Ê66 busy_wait_us(delay_us);
Ê67 }
Ê68 }
Ê69
Ê70 void busy_wait_us(uint64_t delay_us) {
Ê71 uint64_t base = time_us_64();
Ê72 uint64_t target = base + delay_us;
Ê73 if (target < base) {
Ê74 target = (uint64_t)-1;
Ê75 }
Ê76 absolute_time_t t;
Ê77 update_us_since_boot(&t, target);
Ê78 busy_wait_until(t);
Ê79 }
Ê80
Ê81 void busy_wait_ms(uint32_t delay_ms)
Ê82 {
Ê83 if (delay_ms <= 0x7fffffffu / 1000) {
Ê84 busy_wait_us_32(delay_ms * 1000);
Ê85 } else {
Ê86 busy_wait_us(delay_ms * 1000ull);
Ê87 }
Ê88 }
Ê89
Ê90 void busy_wait_until(absolute_time_t t) {
Ê91 uint64_t target = to_us_since_boot(t);
Ê92 uint32_t hi_target = (uint32_t)(target >> 32u);
Ê93 uint32_t hi = timer_hw->timerawh;
Ê94 while (hi < hi_target) {
Ê95 hi = timer_hw->timerawh;
Ê96 tight_loop_contents();
Ê97 }
Ê98 while (hi == hi_target && timer_hw->timerawl < (uint32_t) target) {
Ê99 hi = timer_hw->timerawh;
100 tight_loop_contents();
101 }
102 }
4.6.4.4. Complete example using SDK
Pico Examples: https://github.com/raspberrypi/pico-examples/tree/master/timer/hello_timer/hello_timer.c Lines 11 - 57
11 volatile bool timer_fired = false;
RP2040 Datasheet
4.6. Timer 559