[Gmecm] Any USB developers out there?

[Craig Moates]

Steve,

I've put together an 'alternate' layout for USB-to-VPW. Feel free to take a look. I have yet to stitch together all of the 
connections, but given about an hour or so, it can be cleaned up and made to be pretty tight. Check the readme.txt for comments.

I just did it from scratch, based on the datasheets and takeoffs from what I've done before. But it could be made to be pretty tight 
and workable, and very low cost as well. It doesn't have integrated USB in the micro, but on the other hand, it would be able to use 
standard COM port protocols. You could set it up with a bootloader as well to make it field updateable.

Y'all are welcome to play however you like. I'm going to beat on it some more and get all the connectivity together. Might even hit 
on the firmware if I can find a spare day or two. Ha! Feel free to put it in as part of the Wiki for the GMECM stuff. It's a work in 
progress to be sure, but I figured I'd share what I had thus far.

www.moates.net/projects/class2/

Best regards,
Craig Moates


----- Original Message ----- 
From: "Steve Ravet" <Steve.Ravet at arm.com>
To: <gmecm at diy-efi.org>
Sent: Sunday, November 19, 2006 11:41 PM
Subject: RE: [Gmecm] Any USB developers out there?




> -----Original Message-----
> From: gmecm-bounces at diy-efi.org
> [mailto:gmecm-bounces at diy-efi.org] On Behalf Of Craig Moates
> Sent: Thursday, November 09, 2006 11:51 AM
> To: gmecm at diy-efi.org
> Subject: Re: [Gmecm] Any USB developers out there?
>
> Steve,
>
> Definitely check the crystal and capacitor areas. Those are
> ceramics you are using for the 18pF set? Check that it's set
> up for 18pf on the xtal desired capacitance?

The crystal is 20 MHz 18pf according to the digikey datasheet.  They're
ceramic caps.

I don't know what the problem with the crystal circuit is, but I removed
it and used a 4 MHz OSC instead, changing the firmware accordingly, and
now it works.  I tried with and without the load resistor (on the
crystal) but no change.  The demo board has an external load resistor
but the data sheet shows a resistor internal to the part.

I decided that I want USB power after all so I can reflash the PIC
without external power.  You mentioned the circuit you use but I can't
find the note now.  What is it?

Craig, what do you use for schematic capture and PCB layout?

Maybe there'll be a USB <-> VPW project working by Christmas now...

thanks for the suggestions everyone,

--steve

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