Triode wrote: 
> Just read through the usb section of the data sheet again - it doesn't
> seem to be the same as EHCI, but lets hope it works... EHCI keeps a
> schedule of the next several frames worth of transactions in a shared
> memory block and doesn't require interrupts per packet/frame - it looks
> like this does..  [In contrast the AM37x technical reference manual
> includes all the details of EHCI and register maps I would expect -
> there's definitely a difference between it and the AM335x from the data
> sheet.]
> 
> Lets keep our fingers crossed!  Could you test full speed and high speed
> devices.  There is no mention of split transactions in the datasheet, so
> I wonder how TT works - perhaps if we only have support for native full
> speed or native high speed this does not matter.

How about the AM3874? This is what I was planning on using For Gen2
since it has all the display stuff builtin. According to the technical
manual the USB system DOES have a hardware scheduler, checking the
details you can turn off packet interrupts if using DMA so it looks like
this might be better. 

If this looks like a better USB architecture to use, I could go with
this processor for Gen1 and leave off all the display stuff, just do a
quick and dirty Gen1 implementation. If the USB implementations are
significantly different enough that there are questions about it's
usefullness then it is probably better to use the same processor for
both Gen1 and Gen2. The problem is that I think it's going to take an 8
layer board to do the AM3874, that will add a little more cost to the
board -- I just checked it's only $6 more per board to go with 8 layer.
OK I think I just convinced myself to go with the AM3874 for both Gen1
and Gen2. 

I'll still check and see if the BeagleBone works with the UAC1, UAC2
etc. If it does that probably means that the AM3874 will probably also
work. Unfortunately I have not found out what USB module it uses. I
guess I will have to download the linux SDK and find out! 

John S.


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