Question: What special code changes does my application and firmware require for interrupt endpoint?
When it comes to handling interrupt endpoint, it is very similar to the way bulk endpoint is handled. Here the difference being that the endpoint is declared as type interrupt and you specify a polling period.
The USB stack handles retries on the Endpoint on polling time periods if the Endpoint is NAKing. New requests for IN data must be made by the application after completion of each transfer. The driver polls the endpoint for data only when there is a request for data from the application. The stack drivers handle the polling at regular interval. Therefore the examples that we provide which use bulk endpoint can be easily modified to work with interrupt endpoint. These examples can be found divided in folders as per the product in C:\Cypress\USB\Examples after installing FX2LP DVK and FX2 DVK. In these examples there is a bulktest example for our older parts AN21xx and FX which use interrupt endpoint. All the other examples primarily use bulk endpoint.