RFAL issue

[Marcin_Gasiorek]

Hi,

In the RFAL implementation I found issue where the timer ID is compared with system time.

In the /source/rfal_nfc.c file the following snippet looks suspected (lines from 2288 to 2292):

if( ((platformGetSysTick() + RFAL_NFC_T_FIELD_OFF) > gNfcDev.discTmr) || (aux) ) /* In case Total Duration has expired or expring in less than tFIELD_OFF */
                {
                    platformTimerDestroy( gNfcDev.discTmr );
                    gNfcDev.discTmr = (uint32_t)platformTimerCreate( RFAL_NFC_T_FIELD_OFF );     /* Ensure that Operating Field is in Off condition at least tFIELD_OFF */
                }

 The `discTmr` can contains a timer ID returned by the `platformTimerCreate()` function. When the timer ID value is less than sum of the `platformGetSysTick() + RFAL_NFC_T_FIELD_OFF` it can cause false result on the first condition:

((platformGetSysTick() + RFAL_NFC_T_FIELD_OFF) > gNfcDev.discTmr)

[Brian TIDAL]

Hi,

do you use a bare metal implementation or a RTOS based implementation?

Rgds

BT

[Marcin_Gasiorek]

Hi,

I'm using RTOS based implementation. However I posted here to just communicate the possible issue.

Regards

Marcin

[Brian TIDAL]

Hi,

a bare metal implementation will not be impacted by this issue but a RTOS implementation returning an index or a timeID is likely impacted. I'll report this internally and will keep you posted as soon as a fix or a workaround is available.

Thanks for reporting

Rgds

BT

[Grégoire Poulain · Accepted solution]

Hi,

Thank you for your analysis and reporting.
Your analysis is correct, and indeed this usage is inconsistent with the timer interface.

As Brian detailed before such usage is functional when using the ST provided timer abstraction, where the timer ID/reference is the expiration time/tick itself.
Such arithmetics shall not be performed directly on the timer ID/reference, and the appropriate solution is to make use of an additional API to provide the remaining time until timer expiration.

An upcoming version of the RFAL will incorporate/make use of this new timer API.

For the time being, one can proceed as follow :

((platformGetSysTick() + RFAL_NFC_T_FIELD_OFF) > gNfcDev.discTmr)

// Change to:
(platformTimerGetRemaining(gNfcDev.discTmr) < RFAL_NFC_T_FIELD_OFF)

Where platformTimerGetRemaining() shall return the remaining time (ms) until expiration, for example on FreeRTOS, see the example within  TimerGetExpiryTime.

Kind regards
GP