Callback parameter in stm32 freeRTOS software timer - stm32

Question

I'm trying to use a software timer with cubeMx integration of freeRTOS (basically, it's freeRTOS with a nearly transparent layer above).
I thought I would be able to pass a pointer to a structure as timer parameter and getting it as a parameter in the callback function. Something like this:
typedef struct{
uint8_t a;
uint8_t b;
uint8_t c;
}T;
T t = {1, 2, 3};
osTimerDef(myTimer01, Callback01);
myTimer01Handle = osTimerCreate(osTimer(myTimer01), osTimerPeriodic, (void*) &t);
osTimerStart(myTimer01Handle, 5000);
callback:
void Callback01(void const * argument)
{
T* a = argument;
}
Unfortunately argument does not point to the same address as &t. When I look to freeRTOS code, it appears that the lib passes a structure "Timer_t" casted as void* to the callback function (see end of the code below):
static void prvProcessExpiredTimer( const TickType_t xNextExpireTime, const TickType_t xTimeNow )
{
BaseType_t xResult;
Timer_t * const pxTimer = ( Timer_t * ) listGET_OWNER_OF_HEAD_ENTRY( pxCurrentTimerList );
/* Remove the timer from the list of active timers. A check has already
been performed to ensure the list is not empty. */
( void ) uxListRemove( &( pxTimer->xTimerListItem ) );
traceTIMER_EXPIRED( pxTimer );
/* If the timer is an auto reload timer then calculate the next
expiry time and re-insert the timer in the list of active timers. */
if( pxTimer->uxAutoReload == ( UBaseType_t ) pdTRUE )
{
/* The timer is inserted into a list using a time relative to anything
other than the current time. It will therefore be inserted into the
correct list relative to the time this task thinks it is now. */
if( prvInsertTimerInActiveList( pxTimer, ( xNextExpireTime + pxTimer->xTimerPeriodInTicks ), xTimeNow, xNextExpireTime ) != pdFALSE )
{
/* The timer expired before it was added to the active timer
list. Reload it now. */
xResult = xTimerGenericCommand( pxTimer, tmrCOMMAND_START_DONT_TRACE, xNextExpireTime, NULL, tmrNO_DELAY );
configASSERT( xResult );
( void ) xResult;
}
else
{
mtCOVERAGE_TEST_MARKER();
}
}
else
{
mtCOVERAGE_TEST_MARKER();
}
/* Call the timer callback. */
pxTimer->pxCallbackFunction( ( TimerHandle_t ) pxTimer );
}
The structure is:
typedef struct tmrTimerControl
{
const char *pcTimerName; /*<< Text name. This is not used by the kernel, it is included simply to make debugging easier. */ /*lint !e971 Unqualified char types are allowed for strings and single characters only. */
ListItem_t xTimerListItem; /*<< Standard linked list item as used by all kernel features for event management. */
TickType_t xTimerPeriodInTicks;/*<< How quickly and often the timer expires. */
UBaseType_t uxAutoReload; /*<< Set to pdTRUE if the timer should be automatically restarted once expired. Set to pdFALSE if the timer is, in effect, a one-shot timer. */
void *pvTimerID; /*<< An ID to identify the timer. This allows the timer to be identified when the same callback is used for multiple timers. */
TimerCallbackFunction_t pxCallbackFunction; /*<< The function that will be called when the timer expires. */
} xTIMER;
typedef xTIMER Timer_t;
This structure contains the data pointer I passed when I created the timer. It is stored in pvTimerId.
This means that I should cast the callback parameter as Timer_t in order to have access to pvTimerId. Something like this:
void Callback01(void const * argument)
{
T* a =((Timer_t*)argument)->pvTimerID;
}
BUT this Timer_t structure is not public. I don't really understand why the callback is called with this structure as parameter and moreover casted as const void*...
How should I do?

Answer 1

Considering the call to the osTimerCreate function in your version of cmsis stores realy the argument parameter to the pvTimerID of the Timer_t structure then you could use pvTimerGetTimerID to get your passed data back:
void Callback01(void const * argument)
{
T* data = (T*)pvTimerGetTimerID((TimerHandle_t)argument);
}