random delay

[Ridhi]

I want to add a random delay in range 2000 to 3000 ms before my device perfrom any activity.

pls tell how can do this at earliest

usins some  timer or something else

[Håkon Alseth]

Hi,

 

I want to add a random delay in range 2000 to 3000 ms before my device perfrom any activity.

pls tell how can do this at earliest

usins some  timer or something else

What SDK, and what are you delaying? For nRF5, you can use an app_timer instance for this. For NCS, you can use k_sleep().

 

Kind regards,

Håkon

[Ridhi]

i  am using nrf sdk vrsn 17.1.0 

nrf52832 board softdevc s132.

i  have added simple single shot and repeated timers in the code attached.

i have two nrf 52832 boards and want to add a random timer.

but i dont get how to add a random timer.

i have to do that before timer used in line 357, i should add a  random ms value 

such that one board when works operates with one random value delay while other board works with another random value  

[Håkon Alseth]

Hi,

 

You can setup a one-shot timer with a random value. Here's some pseudo code for you:

uint16_t rand_value;
uint8_t bytes_available = 0;

(void)sd_rand_application_bytes_available_get(&bytes_available);
if (bytes_available >= sizeof(rand_value))
{
    err_code = sd_rand_application_vector_get(&rand_value, sizeof(rand_value));        
    APP_ERROR_CHECK(err_code);
} else {
  /* implement your error handling if no rand bytes available */
}

err_code = app_timer_start(m_my_timer_instance, APP_TIMER_TICKS((rand_value % 1000) + 2000), NULL);
...

You'll need to initialize the app timer instance in addition to the above logic.

  

Kind regards,

Håkon

[Ridhi]

pls tell what is this rand_value, bytes_available

kindly assist me in logic understanding i am new to it.

how to add instance 

also where in my code shared above can i add this so before timer used in line 357

[Håkon Alseth]

You're fetching the amount of random numbers available from the softdevice, and if that number is greater or equal to two 2bytes, you populate the "rand_value" with those random bytes.

Ridhi said:

also where in my code shared above can i add this so before timer used in line 357

It seems that you have already several app_timer instances set up. I would recommend that you follow the same way of initializing and starting the timer, just that you change the functionality to "one shot" here.

Please see the app_timer documentation if anything is unclear: https://infocenter.nordicsemi.com/topic/sdk_nrf5_v17.1.0/lib_timer.html?cp=8_1_3_53

 

Kind regards,

Håkon

[Ridhi]

Hakon i added:

1). defined insatnce:  

APP_TIMER_DEF(m_my_timer_instance);

2). created a single shot timer in timers_init():

err_code = app_timer_create(&m_my_timer_instance,
APP_TIMER_MODE_SINGLE_SHOT,
sensor_timer_handler);
APP_ERROR_CHECK(err_code);

3). now i am not getting how to use this shared by you:

uint16_t rand_value;
uint8_t bytes_available = 0;

(void)sd_rand_application_bytes_available_get(&bytes_available);
if (bytes_available >= sizeof(rand_value))
{
err_code = sd_rand_application_vector_get(&rand_value, sizeof(rand_value));
APP_ERROR_CHECK(err_code);
} else {
/* implement your error handling if no rand bytes available */
}

err_code = app_timer_start(m_my_timer_instance, APP_TIMER_TICKS((rand_value % 1000) + 2000), NULL);

as i dont know how to use it in handler, also i have to add this timer before timer used in line 357 of my code.

pls hlp

[Ridhi]

gentle reminder

[Ridhi]

Hakon pls assist at earliest

[Håkon Alseth]

Could you please explain what is the issue that you are seeing?

 

Kind regards,

Håkon

[Ridhi]

1). in line 158: i have added

APP_TIMER_DEF(m_my_timer_instance);

2). in line 573: i have added

err_code = app_timer_create(&m_my_timer_instance,
APP_TIMER_MODE_SINGLE_SHOT,
battery_level_meas_timeout_handler);
APP_ERROR_CHECK(err_code);

3). i aim to add a random delay before the repeated timer of line 374 starts.

as suggested by you: in line 357 i have added

uint16_t rand_value;
uint8_t bytes_available = 0;

(void)sd_rand_application_bytes_available_get(&bytes_available);
if (bytes_available >= sizeof(rand_value))
{
err_code = sd_rand_application_vector_get(&rand_value, sizeof(rand_value));
APP_ERROR_CHECK(err_code);
} else {
/* implement your error handling if no rand bytes available */
}

err_code = app_timer_start(m_my_timer_instance, APP_TIMER_TICKS((rand_value % 1000) + 2000), NULL);
 

4). i am getting error as shown in pic

5). i am not able to add the random delay

[Håkon Alseth]

The warning you're seeing is due to the types not matching.

You can either cast the input, like so:

        err_code = sd_rand_application_vector_get((uint8_t *)&rand_value, sizeof(rand_value));

or declare rand_value as a uint8_t array: uint8_t rand_value[2];

For the sd_rand_* API to provide you with random bytes, you need to call this after the softdevice has been initialized (ie. after ble_stack_init()).

 

Kind regards,

Håkon