Martin,
> Hi Andreas,
(Just nitpicking, my name is Andras, as in Andr\'as (TeX syntax).)
> As you discovered it, would you mind to explain? My understanding was the
> DISCON pin would float pretty long at H (maybe due to some similar
> soft-pullup like they have on the ports) so it is required to actively
> drive it L. However, I have never used the simple setup with the 1k5
> resistor on USBD+ directly connected to the pin - I've always added a
> transistor there like they did on the development board. So I have never
> seen any issue with disconnect not working.
Ah, OK. I used the 1.5k resistor, no external transistor. I don't know
what the actual cause was, but it looks like the DISCON pin never went
floating or didn't have sufficient impedance for a USB disconnect to
occur. The guys at Cypress recommended setting both DISCON and DISCOE
to 1, thus forcing the pin to go low. I don't think it hurts, so it
might be worth doing for the FX regardless of the version.
How good that they got rid of that external 1.5k resistor in the FX2!
> I cannot tell for the FX2 but I've never seen any problem with INT2CLR or
> INT4CLR. I'm running the FX with up to 100000 interrupts per second,
> mostly USB and GPIF, so I'm pretty sure I would have noticed. I'm sure you
> have it enabled in the USBBAV and INT4SETUP registers respectively?
> And you still need the EXIF first with INTxCLR as well, it's only a
> replacement for the USBIRQ or IN/OUT07IRQ.
Oh, maybe it's worth another try? It's a long time ago that I last
tried, but it caused me days of frustration, so I think I did
everything as it was in the TRM...
> Patches welcome of course ;-)
I'll test it once I have some time.
> Yes it's really a shame they've killed the DMA engine in the FX2. I've
> complained to them and they said it was because the 8051 couldn't keep
> with HS bandwidth anyway. This is right of course but there are other
> benefits f.e. when combining GPIF/FIFO transfer with XMEM buffering, which
> are lost without DMA. In fact this was the main reason not to use the FX2
> in some project recently.
Their idea is that the 8051 is too slow for hi-speed USB anyway, and
how right they are! The FX2 is probably capable of doing everything
the FX could do with DMA, but in a very different way. I think Cypress
didn't make it very easy for FX users to transition to the FX2 because
you have to read at least three full chapters of the TRM to understand
its new philosophy.
Andras
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Major Andras
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www: http://andras.webhop.org/
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