ESP32 Forum

Posted: **Tue Nov 02, 2021 11:54 pm**

I'm trying this example project

/* Timer group-hardware timer example

   This example code is in the Public Domain (or CC0 licensed, at your option.)

   Unless required by applicable law or agreed to in writing, this
   software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
   CONDITIONS OF ANY KIND, either express or implied.
*/

and there is no information on how to stop a timer.

I have found in the online documentation:

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esp_err_t timer_pause(timer_group_t group_num, timer_idx_t timer_num)

    Pause the counter of hardware timer.

So I tried:

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esp_err_t timer_pause(TIMER_GROUP_0, TIMER_1);

or

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esp_err_t timer_pause(timer_group_t TIMER_GROUP_0, timer_idx_t TIMER_1) ;

but none stoped the timer.

How do I do it?
Are the above commands pausing or stopping a timer?
I mean, if I resart the timer later will it restart from zero, or from the value where I paused it?

Thanks

Posted: **Wed Nov 03, 2021 8:05 am**

Hi,
First have a look at your timer configuration. Here is the the configuration I use:

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timer_config_t config;							
	config.alarm_en = TIMER_ALARM_EN;				//Alarm is the value that the timer will count to before rolling over
	config.counter_dir = TIMER_COUNT_UP;
	config.auto_reload = TIMER_AUTORELOAD_EN;
	config.counter_en = TIMER_PAUSE;				//timer_set_counter_value
	config.intr_type = TIMER_INTR_LEVEL;
	config.divider = TIMER_DIVIDER;
	timer_init(TimerGroup, TimerIdx, &config);
	timer_set_counter_value(TimerGroup, TimerIdx, 0x00000000ULL);
	timer_set_alarm_value(TimerGroup, TimerIdx, TIMER_PERIODE);
	timer_enable_intr(TimerGroup, TimerIdx);
	timer_isr_register(TimerGroup, TimerIdx, timer_group0_isr,
       (void *) TimerIdx, Interrupt_Level, NULL);

and when I want to stop the timer I do the following:

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timer_pause(TIMER_GROUP_0, TIMER_1);							//Pause Timer
timer_set_counter_value(TIMER_GROUP_0, TIMER_1, 0x00000000ULL)				//Reset Timer value

Posted: **Wed Nov 03, 2021 9:41 am**

Thank you WardMas

It works perfectly.

And I suppose to restart the same timer later when I need it, I'll do:

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timer_start(TIMER_GROUP_0, TIMER_1);

right?
*******
Any idea why the documentation says:

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esp_err_t timer_pause(TIMER_GROUP_0, TIMER_1);

but in fact we don't need this esp_err_t to make it work?

What is this esp_err_t supposed to do?
I've seen it a lot around, but I can't understand it.

Thanks again

Posted: **Wed Nov 03, 2021 10:21 pm**

HyperUniverse wrote: ↑
Wed Nov 03, 2021 9:41 am
And I suppose to restart the same timer later when I need it, I'll do:
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timer_start(TIMER_GROUP_0, TIMER_1);
right?

That's correct. You may find both methods used e.g. in this example.

HyperUniverse wrote: Any idea why the documentation says:
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esp_err_t timer_pause(TIMER_GROUP_0, TIMER_1);
but in fact we don't need this esp_err_t to make it work?

What is this esp_err_t supposed to do?
I've seen it a lot around, but I can't understand it.

That esp_err_t is the error data type which is in ESP IDF mainly used as a function return data type. From the mentioned timer_pause function reference you can read that this function call will return one of the values described in the Return paragraph (that is either ESP_OK or ESP_ERR_INVALID_ARG).

Whether to check every function return value is a subject to flame and endless war.

For the mentioned function, if you are sure that you will always pass valid parameters to its call, you will never update IDF for possible API changes, earth gravity won't rapidly change or the world won't be attacked by evil aliens, you should be fine to ignore the returned value...

Well, I'd personally check the returned value even in this case (call with valid, constant parameters), even for the price of just wasted CPU ticks for its comparison (which in turn consumes more pointless power and may cause global warming issue even worse).

Posted: **Thu Nov 04, 2021 8:42 am**

Victoria Nope wrote: ↑
Wed Nov 03, 2021 10:21 pm

Thanks for the detailed answer Victoria.

I'll save the planet, as I've been so much indoctrinated by the media, that I've almost started believing it.

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