Feeding an application timer?

RE: Feeding an application timer?

Jørgen Holmefjord — Wed, 14 Oct 2020 13:23:37 GMT

There is no standardized way to do this, as all applications will have different requirements and resources. You need to define some test-cases that will be is expected to put the larges amount of pressure on your application, in terms of high activity, interrupt handling delays, etc.

You can check the utilization of the atomic FIFO using the head and tail parameters of the nrf_atfifo_t instance, which is created inside the NRF_ATFIFO_DEF() macro. You can also just make sure that you do not get the NO_MEM during the stress-testing. You should anyway implement some way of handling this error, in case it should happen anyway in a corner-case you have not thought about.

RE: Feeding an application timer?

nordev — Tue, 13 Oct 2020 17:39:47 GMT

Thanks for the recommendation Jorgen.

[quote userid="14926" url="~/f/nordic-q-a/66910/feeding-an-application-timer/274509#274509"]I would recommend that you profile the FIFO usage in your application during stress-testing to determine the max utilization of the FIFO[/quote]

How do I do this? If you also have links to other resources that explain how to do stress-testing, that would be very helpful.

RE: Feeding an application timer?

Jørgen Holmefjord — Tue, 13 Oct 2020 08:32:56 GMT

A single FIFO is shared by all timers created in the app_timer library. The main limitation is the available RAM in your application/chip. Larger FIFO size will require more static memory.

I would recommend that you profile the FIFO usage in your application during stress-testing to determine the max utilization of the FIFO, and then add some margin on top of that .

RE: Feeding an application timer?

nordev — Tue, 13 Oct 2020 06:01:07 GMT

Thank you so much for the helpful answer, Jorgen.

I see the default queue size is 10, does that mean up to 10 start/stop timer operations can be queued at once, for all timers in the application? Or is this per timer instance?

Is there a practical upper bound or recommended max for how big this queue can be?

Thanks!

RE: Feeding an application timer?

Jørgen Holmefjord — Fri, 09 Oct 2020 12:23:12 GMT

Hi,

[quote user=""]1. how much memory does this queue have, and how much memory does one app_timer_start() or app_timer_stop() operation take?[/quote]

You can configure the size of the operation queue in your sdk_config.h file by setting APP_TIMER_CONFIG_OP_QUEUE_SIZE. This will create an atomic FIFO holding elements of type timer_req_t which holds a pointer to the timer instance and the request type:

/**
 * @brief Timer requests types.
 */
typedef enum
{
    TIMER_REQ_START,
    TIMER_REQ_STOP,
    TIMER_REQ_STOP_ALL
} app_timer_req_type_t;

/**
 * @brief Operation request structure.
 */
typedef struct
{
    app_timer_req_type_t type;    /**< Request type. */
    app_timer_t *        p_timer; /**< Timer instance. */
} timer_req_t;

/* Request FIFO instance. */
NRF_ATFIFO_DEF(m_req_fifo, timer_req_t, APP_TIMER_CONFIG_OP_QUEUE_SIZE);

[quote user=""]2. is there a way to modify the timer register to feed the timer directly?[/quote]

As far as I can see, there is currently no such functionality in the app_timer implementation.

Best regards,
Jørgen