Author Topic: rejecting usbFunctionSetup request?  (Read 266 times)

ulao

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rejecting usbFunctionSetup request?
« on: July 01, 2017, 04:33:46 pm »
If i wanted to set a busy flag in my USB firmware so that any request feature or normal get/set request is rejected, could I some how return data that would force an error?

Or would I have to return some flagged data in my payload to catch on the receiving end?

a)
usbMsgLen_t  usbFunctionSetup(uchar data[8])
{      
   if (_BUSY) return 0; //reject with 0
...

b)
usbMsgLen_t  usbFunctionSetup(uchar data[8])
{      
   if (_BUSY) { Buffer[0xff] return 0; } //reject with first byte of FF to tell the software there we are busy.
...

As it stands if the USB has some type of  error (i.e. PID STALL) it returns an error and I catch that in my code. I'm just not sure how error handling works.  I'm pretty sure the return to usbFunctionSetup is the length of the data. Guessing a return of 0 means data length of 8 but not sure.

usbMsgLen_t is my return type for usbFunctionSetup
usbMsgPtr points to my payload array
I don't see any room for error handling.

« Last Edit: July 01, 2017, 11:20:22 pm by ulao »

Jan Axelson

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Re: rejecting usbFunctionSetup request?
« Reply #1 on: July 01, 2017, 04:52:18 pm »
STALL means request not supported.

NAK means busy (temporary state).

For a vendor-defined Get_Feature request, you can define codes for the firmware to return to indicate "rejected" or other conditions.

Not sure if that answers your question.

ulao

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Re: rejecting usbFunctionSetup request?
« Reply #2 on: July 01, 2017, 11:20:08 pm »
it helps a bit, so I'm trying to figure out how to get my firmware to report NAK (aka busy) based on some condition. I'm just not certain no how I can return this via code(firmware). This may be a question for the usb firmware API...

« Last Edit: July 01, 2017, 11:22:18 pm by ulao »

Jan Axelson

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Re: rejecting usbFunctionSetup request?
« Reply #3 on: July 03, 2017, 09:11:19 am »
How to return NAK varies with the chip architecture as defined in the data sheet.