[hpsdr] FW: hpsdr] [FPGA_USB] Review/Comments FPGA_USB Board -April 5, 2006

[Phil Harman]

Phil,

Yes, the PIC 18F4550 uses the Windows  USB COM port drivers so it just looks 
like an additional COM port when you plug it in.

Phil...
----- Original Message ----- 
From: "Philip Covington" <p.covington at gmail.com>
To: "Christopher T. Day" <CTDay at lbl.gov>
Cc: <pvharman at arach.net.au>; "High Performance Software Defined Radio 
Discussion List" <hpsdr at hpsdr.org>
Sent: Thursday, April 13, 2006 9:20 PM
Subject: Re: [hpsdr] FW: hpsdr] [FPGA_USB] Review/Comments FPGA_USB 
Board -April 5, 2006


On 4/13/06, Christopher T. Day <CTDay at lbl.gov> wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> Phil,
>
> I'm sure any code you have would be really useful. I'd love to have it.
> Not having a good compiler will clearly be a pain, though.
>
> I'm not sure I fully understand your comment that the USB port has to be
> "polled". From my reading of the spec, I would have thought that with
> the Transfer Complete interrupt bit, TRNIE, enabled you'd be interrupt
> driven, and using the PingPong Buffering would mean that you always
> owned a buffer to work with for the interrupting endpoint. True, if
> you're trying to send an audio stream with Bulk Transfers - I guess the
> only thing possible over something that looks like a COM port at the PC
> end - you'll be really busy moving the data around. But then I get to
> jump back on my Isochronous Transfer hobby-horse and claim that's how
> the transfers should be done; then I could enable the Streaming Serial
> Port, hand that descriptor permanently over to the USB engine and the
> CPU wouldn't be involved in the audio transfers at all. Of course, there
> would have to be something with some intelligence attached to the SSP,
> but don't we all believe we're supposed to heave an FPGA or CPLD or
> something like that at that part of the problem?
>
> Anyway, this is rather early-morning, pre-coffee ramblings for me, so it
> could easily make no sense.
>
>
>         Chris - AE6VK

I know this was addressed to Phil H, but here are a few questions:

[WARNING I've not looked at the 18F4450 at all so this might be stupid]

Does the PIC look like a COM port because of its driver?  Could we use
something like libUSB to talk to the PIC and avoid loading its
supplied driver?  Just some thoughts...

Also, as far as Iso mode, with high speed USB the preferred method is
most always block transfers.  Iso was more important for USB 1.1.

73 de Phil N8VB



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