wangchdo opened a new pull request, #17065:
URL: https://github.com/apache/nuttx/pull/17065
Add a high resolution timer module in sched
to support hard real time cases
*Note: Please adhere to [Contributing
Guidelines](https://github.com/apache/nuttx/blob/master/CONTRIBUTING.md).*
## Summary
Nuttx only provide wdog for delayed function execution, wdog is mainly used
for OS-internal timeouts (e.g., task scheduling, time slicing) and periodic
callbacks. Resolution depends on system tick.
This PR introduces hrtimer to Nuttx acting as a high-resolution timer, it
can deliver deliver precise timing events (nanosecond or microsecond accuracy).
**Aspect | NuttX hrtimer
| NuttX wdog
--------------------+---------------------------------------------------------------------+---------
Purpose | High-resolution timer |
Lightweight software timer
| for precise event scheduling.
| for delayed callbacks and OS timeouts.
Resolution | Nanosecond / microsecond accuracy, | tick-based (ms
level)
| independent of system tick. |
Accuracy | Very high, suitable for |
Limited by system tick;
| hard real-time and
| not sufficient for hard real-time control.
| multimedia workloads.
Implementation | min-queue tree for timers. | Linked
list of timers, sorted by expiration,
| sorted by expiration,
| integrated into scheduler.
Usage Pattern | Create `hrtimer_int()`, |
Allocate `wdog_t`,
| start with `hrtimer_start()`,
| start with `wd_start()`,
| cancel with `hrtimer_cancel()`.
| cancel with `wd_cancel()`.
Callback Context | Runs in interrupt |
Runs in interrupt context
| context
|(scheduler tick or hrtimer).
Use Cases | Precise scheduling, |
Task time slicing,
| hard RT tasks, multimedia,
| timeout handling,
| networking,
| simple periodic events.
| low-latency wake-ups.
Complexity | A little Complex |
Simple and lightweight;
| but optimized for embedded RTOS,
| no rb-tree, but use priority-queue
Footprint | Larger memory and CPU overhead. | Minimal
memory and CPU usage.**
## Impact
A new module added in sched,
**if it is enabled:**
1. new functions will be introduced, hrtimer_init(), hrtimer_start(),
hrtimer_cancel()
2. wdog will be driven by hrtimer as a timer
**if it is not enabled:**
nothing happen
## Testing
**enable** hrtimer in a2g-tc397-5v-tft:
<img width="699" height="529" alt="image"
src="https://github.com/user-attachments/assets/d5a88118-e8a0-4c57-98e3-1fb920deb45f";
/>
**ostest passed**
<img width="649" height="714" alt="image"
src="https://github.com/user-attachments/assets/7cfa7afa-b527-4d41-a28b-a92f00e480b3";
/>
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