Handling of Wait Time Extension (WTX)

[DGabc.1]

Hi,

In ST25RFAL library, version 2.8.0, in rfal_isoDep.c, function rfalIsoDepHandleControlMsg(), when ISODEP_S_WTX messages is handled, the code limits how many times a card can request wait time extension, specifically, this line:

 

 

if( (gIsoDep.cntSWtxRetrys++ > gIsoDep.maxRetriesSWTX) && (gIsoDep.maxRetriesSWTX != RFAL_ISODEP_MAX_WTX_RETRYS_ULTD) )

 

 

 

By default it limits to 20 (RFAL_ISODEP_MAX_WTX_RETRYS) wait time extension requests.

What is the reason for having such a limit?

Thank you,

D.

[Brian TIDAL]

Hi,

this is to prevent the Reader/Writer from being blocked by arbitrarily long Listener processing times as stated in NFC Forum Digital Protocol v2.0 16.2.5.2.

Anyway, this is configurable through rfalIsoDepInitializeWithParams() if your application needs to support more retries. 

Feel free to share more details about your application, in particular about your need for more WTX retries.

Rgds

BT