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WICED Smart Bluetooth

Anonymous
Not applicable

At the moment the lowest finetimer setting is 12.5msec.

Can i adjust this to lower value like 1msec?

Maybe by patching the cortex m3 registers directly ?

1 Solution
ArvindS_76
Employee

The 1s app timer and the fine timer are software times and the resolution if the fine timer is 12.5mS. This cannot be changed.

With SDK 2.x, there is a different timer that can run at a resolution of 1.25mS as an optional library you can add to the app. See <SDK>/Wiced-Smart/tier2/brcm/libraries/inc/bt_clock_based_timer.h

To include this library to your application, add the following line to your application's makefile.mk:

# Include this library to the application.

APP_PATCHES_AND_LIBS += bt_clock_based_periodic_timer.a

Then initialize the library in your application_create function before starting the timer:

#include "bleappevent.h"

#include "bt_clock_based_timer.h"

void application_create(void)

{

     //// All other application initialization here.

     // Initialize the BT clock based periodic timer library

     bt_clock_based_periodic_timer_Init();

}

Then to start the timer at say 50mS interval:

void application_start_50ms_timer(void)

{

     // See header for more details

     bt_clock_based_periodic_timer_Enable(application_timer_expired_callback, NULL, 50000/625)

}

int application_timer_expired_callback(void* context)

{

     // 50 ms timer callback, do something.

     // Context was not allocated and so does not need to be freed. So return no action.

     return BLE_APP_EVENT_NO_ACTION;

}

To stop timer, use bt_clock_based_periodic_timer_Disable()

View solution in original post

9 Replies
ArvindS_76
Employee

The 1s app timer and the fine timer are software times and the resolution if the fine timer is 12.5mS. This cannot be changed.

With SDK 2.x, there is a different timer that can run at a resolution of 1.25mS as an optional library you can add to the app. See <SDK>/Wiced-Smart/tier2/brcm/libraries/inc/bt_clock_based_timer.h

To include this library to your application, add the following line to your application's makefile.mk:

# Include this library to the application.

APP_PATCHES_AND_LIBS += bt_clock_based_periodic_timer.a

Then initialize the library in your application_create function before starting the timer:

#include "bleappevent.h"

#include "bt_clock_based_timer.h"

void application_create(void)

{

     //// All other application initialization here.

     // Initialize the BT clock based periodic timer library

     bt_clock_based_periodic_timer_Init();

}

Then to start the timer at say 50mS interval:

void application_start_50ms_timer(void)

{

     // See header for more details

     bt_clock_based_periodic_timer_Enable(application_timer_expired_callback, NULL, 50000/625)

}

int application_timer_expired_callback(void* context)

{

     // 50 ms timer callback, do something.

     // Context was not allocated and so does not need to be freed. So return no action.

     return BLE_APP_EVENT_NO_ACTION;

}

To stop timer, use bt_clock_based_periodic_timer_Disable()

View solution in original post

Anonymous
Not applicable

I am using BCM920737TAG board and the timer works with 2.5msec configuration.

bt_clock_based_periodic_timer_Enable(application_timer_expired_callback, NULL, 2500/625); -- works

But it doesn't work with 1.25msec configuration

bt_clock_based_periodic_timer_Enable(application_timer_expired_callback, NULL, 1250/625);

I am toggling one of port pin to monitor the timing

int application_timer_expired_callback(void* context)

{

     // 50 ms timer callback, do something.

    if(gpio_getPinOutput(APPLICATION_LED_GREEN_PORT, APPLICATION_LED_GREEN_PIN) == APPLICATION_LED_GREEN_ON)

  {

       application_turn_off_green_led();

  }

  else

  {

       application_turn_on_green_led();

  }

     // Context was not allocated and so does not need to be freed. So return no action.

     return BLE_APP_EVENT_NO_ACTION;

}

Is there any limitation on using 1.25msec as timer period?

0 Likes
ArvindS_76
Employee

Periods of less than ~5mS should not be used because this will severely affect connections/advertisements/scans. This timer uses the BT scheduler which runs off BT slots (625uS). Since most things BT are scheduled in periods of slots or frames (1.25mS), setting this timer to 1.25mS won't work because there are higher priority tasks that the BT scheduler has to perform and will always preempt this timer.

Anonymous
Not applicable

Is it possible t read the slot count(625usec) form application?

0 Likes
ArvindS_76
Employee

No, this is not possible.

Anonymous
Not applicable

Thanks for information and I need more information about this timer.

I want to configure this timer for 5msec and in call back function I want to execute my application code. Is there any limitation how much code we can execute without effecting the performance.

0 Likes
ArvindS_76
Employee

The callback is serialized to the application thread. Since all time critical activity happens in interrupt context, you should be OK to use say 3-4mS of the processing time. Just remember that it is the idle thread that pets the watch dog (WD). If you don't let the idle thread run at least once in 2s, you will trip the watchdog and the chip will reset (you can pet the WD using wdog_restart() in your app code, but you should be a bit careful with this approach).

Also remember that there are a number of commands and events the BT stack will need to handle (the stack runs in the same thread context). Your app will also need to handle other callbacks and interrupt handlers and these are also serialized to the application thread. So you cannot take up all the processing time in this timer callback (and you have to return from this function).

Anonymous
Not applicable

Can i use SDK 2...  for a 20732s Design? Is there a solution for SDK 1.1?

0 Likes
MichaelF_56
Moderator
Moderator

Unfortunately, you will need to use SDK 1.1 for BCM20732S designs.  I will let the development team respond with a work around if one exists.

0 Likes