How to USB in combination with a barcode scanner (as a host only peripheral for reading)?

[wh_it_11193]

I have a USB device in HOST only mode using the CDC middleware to receive data from a barcode scanner set in RS232 mode. This is working accept for the enormous amount of (spurious) host channels interrupt USB_OTG_GINTSTS_HCINT. When I monitor the number of received interrupt they add up to more 65000 a second. This will have a real bad influence on the rest of the system behavior. I there anyone who had the same experience? Is there a good example somewhere that show the right way to do it?

(When I disable the USB_OTG_GINTSTS_HCINT interrupt the performance improves but then I don't receive any data anymore)

Thanks in advance

Wim

[waclawek.jan]

Which STM32?

This is most probably the infamous "NAK flood" - when a bulk endpoint in the device does not have data to send or can't receive more data, it NAKs the host's request; but the handler in Cube upon receiving the NAK immediately retries again. This has been discussed here already.

There's no hardware support for scheduling this in some less aggressive manner; in software, the solution is to avoid retrying communication at the given endpoint for some time. I know this may be not simple and even less so, if you use some ready-made library such as Cube. In the thread linked above, there is a solution offered in the form of disabling NAK interrupts when they occur the first time, and then reenabling them at SOF; I personally don't use it but IMO this may work satisfactorily probably for most practical applications.

JW

[wh_it_11193]

Thank you for the answer!!! Looks like this is the problem. By the way I'm using the STM32L476 device. I'll dive into the discussion link to see how I can solve the problem. Perhaps someone out there already has some example code available. It would really help me out.

Thanks again,

Wim