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Support absolute timings for ESP Timer (High Resolution Timer) (IDFGH-16718) #17807

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Support absolute timings for ESP Timer (High Resolution Timer) (IDFGH-16718) #17807

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0a18c4a
feat(esp_timer): support absolute timings
robot-controller Oct 31, 2025
a217dbf
feat(esp_timer): show absolute timings in example
robot-controller Oct 31, 2025
e788b4e
fix(esp_timer): reject illegal alarm times
robot-controller Nov 10, 2025
0a3bdda
feat(esp_timer): reflect absolute timing features in test
robot-controller Nov 10, 2025
80516c2
feat(esp_timer): reflect absolute timing feature in docs
robot-controller Nov 10, 2025
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58 changes: 57 additions & 1 deletion components/esp_timer/include/esp_timer.h
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
/*
* SPDX-FileCopyrightText: 2017-2024 Espressif Systems (Shanghai) CO LTD
* SPDX-FileCopyrightText: 2017-2025 Espressif Systems (Shanghai) CO LTD
*
* SPDX-License-Identifier: Apache-2.0
*/
Expand Down Expand Up @@ -157,6 +157,22 @@ esp_err_t esp_timer_create(const esp_timer_create_args_t* create_args,
*/
esp_err_t esp_timer_start_once(esp_timer_handle_t timer, uint64_t timeout_us);

/**
* @brief Start a one-shot timer
*
* Timer represented by `timer` should not be running when this function is
* called.
*
* @param timer timer handle created using esp_timer_create()
* @param alarm_us timer alarm time, in absolute microseconds (as returned by
* esp_timer_get_time())
* @return
* - ESP_OK on success
* - ESP_ERR_INVALID_ARG if the handle is invalid
* - ESP_ERR_INVALID_STATE if the timer is already running
*/
esp_err_t esp_timer_start_once_at(esp_timer_handle_t timer, uint64_t alarm_us);

/**
* @brief Start a periodic timer
*
Expand All @@ -172,6 +188,26 @@ esp_err_t esp_timer_start_once(esp_timer_handle_t timer, uint64_t timeout_us);
*/
esp_err_t esp_timer_start_periodic(esp_timer_handle_t timer, uint64_t period);

/**
* @brief Start a periodic timer
*
* Timer represented by `timer` should not be running when this function is called.
* This function starts the timer which will trigger every `period` microseconds.
* The first alarm will be triggered at `first_alarm_us` time.
*
* @param timer timer handle created using esp_timer_create()
* @param period_us timer period, in microseconds
* @param first_alarm_us timer first alarm time, in absolute microseconds (as
* returned by esp_timer_get_time())
* @return
* - ESP_OK on success
* - ESP_ERR_INVALID_ARG if the handle is invalid
* - ESP_ERR_INVALID_STATE if the timer is already running
*/
esp_err_t esp_timer_start_periodic_at(esp_timer_handle_t timer,
uint64_t period_us,
uint64_t first_alarm_us);

/**
* @brief Restart a currently running timer
*
Expand All @@ -190,6 +226,26 @@ esp_err_t esp_timer_start_periodic(esp_timer_handle_t timer, uint64_t period);
*/
esp_err_t esp_timer_restart(esp_timer_handle_t timer, uint64_t timeout_us);

/**
* @brief Restart a currently running timer
*
* Type of `timer` | Action
* --------------- | ------
* One-shot timer | Restarted immediately and times out once at `alarm_us` microseconds
* Periodic timer | Restarted immediately with a new period of `timeout_us` microseconds. Next alarm is at `alarm_us` microseconds
*
* @param timer timer handle created using esp_timer_create()
* @param period_us In case of a periodic timer, represents the new period.
* @param alarm_us timer alarm time, in absolute microseconds (as returned by
* esp_timer_get_time())
* @return
* - ESP_OK on success
* - ESP_ERR_INVALID_ARG if the handle is invalid
* - ESP_ERR_INVALID_STATE if the timer is not running
*/
esp_err_t esp_timer_restart_at(esp_timer_handle_t timer, uint64_t period_us,
uint64_t alarm_us);

/**
* @brief Stop a running timer
*
Expand Down
81 changes: 75 additions & 6 deletions components/esp_timer/src/esp_timer.c
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,13 @@ static bool timer_armed(esp_timer_handle_t timer);
static void timer_list_lock(esp_timer_dispatch_t timer_type);
static void timer_list_unlock(esp_timer_dispatch_t timer_type);

static esp_err_t esp_timer_start_once_at_impl(esp_timer_handle_t timer,
uint64_t alarm_us);
static esp_err_t esp_timer_start_periodic_at_impl(esp_timer_handle_t timer,
uint64_t period_us,
uint64_t first_alarm_us);
static esp_err_t esp_timer_restart_at_impl(esp_timer_handle_t timer, uint64_t timeout_us, uint64_t alarm_us);

#if WITH_PROFILING
static void timer_insert_inactive(esp_timer_handle_t timer);
static void timer_remove_inactive(esp_timer_handle_t timer);
Expand Down Expand Up @@ -134,8 +141,19 @@ esp_err_t esp_timer_create(const esp_timer_create_args_t* args,
*/
esp_err_t ESP_TIMER_IRAM_ATTR esp_timer_restart(esp_timer_handle_t timer, uint64_t timeout_us)
{
esp_err_t ret = ESP_OK;
if (timer == NULL) {
return ESP_ERR_INVALID_ARG;
}

if (!is_initialized() || !timer_armed(timer)) {
return ESP_ERR_INVALID_STATE;
}

return esp_timer_restart_at_impl(timer, timeout_us, 0);
}

esp_err_t ESP_TIMER_IRAM_ATTR esp_timer_restart_at(esp_timer_handle_t timer, uint64_t period_us, uint64_t alarm_us)
{
if (timer == NULL) {
return ESP_ERR_INVALID_ARG;
}
Expand All @@ -144,6 +162,14 @@ esp_err_t ESP_TIMER_IRAM_ATTR esp_timer_restart(esp_timer_handle_t timer, uint64
return ESP_ERR_INVALID_STATE;
}

return esp_timer_restart_at_impl(timer, period_us, alarm_us);
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@KonstantinKondrashov KonstantinKondrashov Nov 4, 2025

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Seems like we have to check alarm_us, != 0, and greater than the current time, and return an error.
For all 3 functions.

}

static esp_err_t ESP_TIMER_IRAM_ATTR
esp_timer_restart_at_impl(esp_timer_handle_t timer, uint64_t timeout_us, uint64_t alarm_us)
{
esp_err_t ret = ESP_OK;

esp_timer_dispatch_t dispatch_method = timer->flags & FL_ISR_DISPATCH_METHOD;
timer_list_lock(dispatch_method);

Expand All @@ -169,6 +195,12 @@ esp_err_t ESP_TIMER_IRAM_ATTR esp_timer_restart(esp_timer_handle_t timer, uint64
timer->alarm = now + timeout_us;
timer->period = 0;
}

/* If the alarm time is explicitly specified, override the calculated one */
if (alarm_us != 0) {
timer->alarm = alarm_us;
}

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@cursor cursor bot Oct 31, 2025

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Bug: Deadlock in esp_timer_restart_at_impl with timer_lock

The esp_timer_restart_at_impl function causes a deadlock by calling timer_remove while already holding the non-recursive timer_list_lock. It also inconsistently ignores an alarm_us value of 0, preventing absolute alarm times at boot, unlike other _at timer functions.

Fix in Cursor Fix in Web

ret = timer_insert(timer, false);
}

Expand All @@ -185,7 +217,23 @@ esp_err_t ESP_TIMER_IRAM_ATTR esp_timer_start_once(esp_timer_handle_t timer, uin
if (!is_initialized()) {
return ESP_ERR_INVALID_STATE;
}
int64_t alarm = esp_timer_get_time() + timeout_us;
return esp_timer_start_once_at_impl(timer, esp_timer_get_time() + timeout_us);
}

esp_err_t ESP_TIMER_IRAM_ATTR esp_timer_start_once_at(esp_timer_handle_t timer, uint64_t alarm_us)
{
if (timer == NULL) {
return ESP_ERR_INVALID_ARG;
}
if (!is_initialized()) {
return ESP_ERR_INVALID_STATE;
}
return esp_timer_start_once_at_impl(timer, alarm_us);
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@KonstantinKondrashov KonstantinKondrashov Nov 4, 2025

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Add the check of alarm_us

}

static ESP_TIMER_IRAM_ATTR esp_err_t
esp_timer_start_once_at_impl(esp_timer_handle_t timer, uint64_t alarm_us)
{
esp_timer_dispatch_t dispatch_method = timer->flags & FL_ISR_DISPATCH_METHOD;
esp_err_t err;

Expand All @@ -199,7 +247,7 @@ esp_err_t ESP_TIMER_IRAM_ATTR esp_timer_start_once(esp_timer_handle_t timer, uin
if (timer_armed(timer)) {
err = ESP_ERR_INVALID_STATE;
} else {
timer->alarm = alarm;
timer->alarm = alarm_us;
timer->period = 0;
#if WITH_PROFILING
timer->times_armed++;
Expand All @@ -210,7 +258,22 @@ esp_err_t ESP_TIMER_IRAM_ATTR esp_timer_start_once(esp_timer_handle_t timer, uin
return err;
}

esp_err_t ESP_TIMER_IRAM_ATTR esp_timer_start_periodic(esp_timer_handle_t timer, uint64_t period_us)
esp_err_t ESP_TIMER_IRAM_ATTR esp_timer_start_periodic_at(
esp_timer_handle_t timer, uint64_t period_us, uint64_t first_alarm_us)
{
if (timer == NULL) {
return ESP_ERR_INVALID_ARG;
}
if (!is_initialized()) {
return ESP_ERR_INVALID_STATE;
}

period_us = MAX(period_us, esp_timer_impl_get_min_period_us());
return esp_timer_start_periodic_at_impl(timer, period_us, first_alarm_us);
}

esp_err_t ESP_TIMER_IRAM_ATTR esp_timer_start_periodic(esp_timer_handle_t timer,
uint64_t period_us)
{
if (timer == NULL) {
return ESP_ERR_INVALID_ARG;
Expand All @@ -219,7 +282,13 @@ esp_err_t ESP_TIMER_IRAM_ATTR esp_timer_start_periodic(esp_timer_handle_t timer,
return ESP_ERR_INVALID_STATE;
}
period_us = MAX(period_us, esp_timer_impl_get_min_period_us());
int64_t alarm = esp_timer_get_time() + period_us;
return esp_timer_start_periodic_at_impl(timer, period_us,
esp_timer_get_time() + period_us);
}

static ESP_TIMER_IRAM_ATTR esp_err_t esp_timer_start_periodic_at_impl(
esp_timer_handle_t timer, uint64_t period_us, uint64_t first_alarm_us)
{
esp_timer_dispatch_t dispatch_method = timer->flags & FL_ISR_DISPATCH_METHOD;
esp_err_t err;
timer_list_lock(dispatch_method);
Expand All @@ -228,7 +297,7 @@ esp_err_t ESP_TIMER_IRAM_ATTR esp_timer_start_periodic(esp_timer_handle_t timer,
if (timer_armed(timer)) {
err = ESP_ERR_INVALID_STATE;
} else {
timer->alarm = alarm;
timer->alarm = first_alarm_us;
timer->period = period_us;
#if WITH_PROFILING
timer->times_armed++;
Expand Down
99 changes: 68 additions & 31 deletions examples/system/esp_timer/README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -86,36 +86,73 @@ If you see the following console output, your example should be running correctl

```
...
I (294) example: Started timers, time since boot: 9662 us
periodic 500000 509644 1 0 0 0
one-shot 0 5009654 1 0 0 0
I (794) example: Periodic timer called, time since boot: 509694 us
I (1294) example: Periodic timer called, time since boot: 1009671 us
I (1794) example: Periodic timer called, time since boot: 1509671 us
I (2294) example: Periodic timer called, time since boot: 2009671 us
periodic 500000 2509644 1 4 0 542
one-shot 0 5009654 1 0 0 0
I (2794) example: Periodic timer called, time since boot: 2509671 us
I (3294) example: Periodic timer called, time since boot: 3009671 us
I (3794) example: Periodic timer called, time since boot: 3509671 us
I (4294) example: Periodic timer called, time since boot: 4009671 us
periodic 500000 4509644 1 8 0 1026
one-shot 0 5009654 1 0 0 0
I (4794) example: Periodic timer called, time since boot: 4509671 us
I (5294) example: Periodic timer called, time since boot: 5009669 us
I (5294) example: One-shot timer called, time since boot: 5009788 us
I (5294) example: Restarted periodic timer with 1s period, time since boot: 5012675 us
I (6294) example: Periodic timer called, time since boot: 6012692 us
periodic 1000000 7012666 2 11 0 1391
one-shot 0 0 1 1 0 11472
I (7294) example: Periodic timer called, time since boot: 7012692 us
I (8294) example: Periodic timer called, time since boot: 8012692 us
periodic 1000000 9012666 2 13 0 1639
one-shot 0 0 1 1 0 11472
I (9294) example: Periodic timer called, time since boot: 9012692 us
I (10294) example: Periodic timer called, time since boot: 10012692 us
I (10314) example: Entering light sleep for 0.5s, time since boot: 10024351 us
I (10314) example: Woke up from light sleep, time since boot: 10525143 us
I (266) example: Started timers, time since boot: 30808 us
Timer stats:
Name Period Alarm Times_armed Times_trigg Times_skip Cb_exec_time
periodic 500000 530773 1 0 0 0
timed periodic 500000 3000000 1 0 0 0
one-shot 0 5030792 1 0 0 0
timed one-shot 0 6000000 1 0 0 0
I (766) example: Periodic timer called, time since boot: 530850 us
I (1266) example: Periodic timer called, time since boot: 1030802 us
I (1766) example: Periodic timer called, time since boot: 1530802 us
I (2266) example: Periodic timer called, time since boot: 2030802 us
Timer stats:
Name Period Alarm Times_armed Times_trigg Times_skip Cb_exec_time
periodic 500000 2530773 1 4 0 999
timed periodic 500000 3000000 1 0 0 0
one-shot 0 5030792 1 0 0 0
timed one-shot 0 6000000 1 0 0 0
I (2766) example: Periodic timer called, time since boot: 2530826 us
I (3236) example: Timed periodic timer called, time since boot: 3000029 us
I (3266) example: Periodic timer called, time since boot: 3030802 us
I (3736) example: Timed periodic timer called, time since boot: 3500029 us
I (3766) example: Periodic timer called, time since boot: 3530802 us
I (4236) example: Timed periodic timer called, time since boot: 4000029 us
I (4266) example: Periodic timer called, time since boot: 4030802 us
Timer stats:
Name Period Alarm Times_armed Times_trigg Times_skip Cb_exec_time
timed periodic 500000 4500000 1 3 0 709
periodic 500000 4530773 1 8 0 1947
one-shot 0 5030792 1 0 0 0
timed one-shot 0 6000000 1 0 0 0
I (4736) example: Timed periodic timer called, time since boot: 4500053 us
I (4766) example: Periodic timer called, time since boot: 4530802 us
I (5236) example: Timed periodic timer called, time since boot: 5000030 us
I (5266) example: Periodic timer called, time since boot: 5030803 us
I (5266) example: One-shot timer called, time since boot: 5031025 us
I (5266) example: Restarted periodic timer with 1s period, time since boot: 5031920 us
I (5736) example: Timed periodic timer called, time since boot: 5500029 us
I (6236) example: Timed one-shot timer called, time since boot: 6000028 us
I (6236) example: Restarted timed periodic timer with 1s period, time since boot: 6000268 us
I (6266) example: Periodic timer called, time since boot: 6031945 us
Timer stats:
Name Period Alarm Times_armed Times_trigg Times_skip Cb_exec_time
timed periodic 1000000 7000000 1 6 0 1438
periodic 1000000 7031916 2 11 0 2644
timed one-shot 0 0 1 1 0 3722
one-shot 0 0 1 1 0 8517
I (7236) example: Timed periodic timer called, time since boot: 7000053 us
I (7266) example: Periodic timer called, time since boot: 7031945 us
I (8236) example: Timed periodic timer called, time since boot: 8000029 us
I (8266) example: Periodic timer called, time since boot: 8031945 us
Timer stats:
Name Period Alarm Times_armed Times_trigg Times_skip Cb_exec_time
timed periodic 1000000 9000000 1 8 0 1940
periodic 1000000 9031916 2 13 0 3106
timed one-shot 0 0 1 1 0 3722
one-shot 0 0 1 1 0 8517
I (9236) example: Timed periodic timer called, time since boot: 9000053 us
I (9266) example: Periodic timer called, time since boot: 9031945 us
I (10236) example: Timed periodic timer called, time since boot: 10000029 us
I (10266) example: Periodic timer called, time since boot: 10031945 us
I (10476) example: Entering light sleep for 0.5s, time since boot: 10239360 us
I (10476) example: Woke up from light sleep, time since boot: 10739673 us
I (10736) example: Timed periodic timer called, time since boot: 11000033 us
I (10766) example: Periodic timer called, time since boot: 11031945 us
I (11736) example: Timed periodic timer called, time since boot: 12000029 us
I (11766) example: Periodic timer called, time since boot: 12031945 us
I (12486) example: Stopped and deleted timers
...
```

Expand All @@ -127,7 +164,7 @@ The subsections below walk you through the important parts of the application ex

### Creating Callback Functions

Timers are used to execute a callback function as a delayed action. So the callback functions `periodic_timer_callback()` and `oneshot_timer_callback()` are crucial parts of this application example.
Timers are used to execute a callback function as a delayed action. So the callback functions `periodic_timer_callback()`, `timed_periodic_timer_callback()`, `oneshot_timer_callback()` and `timed_oneshot_timer_callback()`, are crucial parts of this application example.


### Printing Timer Dumps
Expand Down
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