USB Microframe interrupt?

Hi Amit,

I have weird findings regarding SOF on TM4C1294 test:

For example, from USB interrupt, I see SOFs of 1,2,3,4,5,6,......

but once a while,

1) I will see 1,2,3,4,0,0,0,8, 9..., SOF of 0 in place of the missing 5, 6 and 7
2) and I also saw 1,2,3,4,4,6,7,8... a duplicated SOF of 4 in place of the missing 5

Could this be some bugs in TM4C1294's USB module or stack? (btw, My coworker uses Renesas, and he said Renesas' USB will take care case 1 which is usually caused by broken USB packets, but he never saw case 2.)

Thanks for your time!

David

Hello David

Where are you seeing the SOF's? Is it on a LeCroy or some variable in the USB module stack?

Regards
Amit

In startup_ccs.c, I hooked the following to USB interrupt vector, and traps non-sequential SOFs

HWREGH(USB0_BASE + USB_O_FRAME);

Hello David,

Can you double check this against a USB Tester to make sure that the FRAME numbers are incrementing correctly on the bus as they get captured?

Regards
Amit

Unfortunately I don't have a USB tester :(

Hello David,

Is this USB Full Speed Frame?

Regards
Amit

Yes, it is Full Speed

Hello David,

Is the strange SOF sequence creating a software issue?

Regards
Amit

Not obvious, it seems to affect the throughput rate, but I can't be 100% sure yet

It is more an application issue

Hello David,

It would be a host controller issue if the SOF sequencing is incorrect. I believe snooping the USB Bus should give a more definitive answer,

Regards
Amit

OK, I will looking into that and let you know if I can find out more about it

Have a nice weekend!