[Gmecm] Any USB developers out there?

[Craig Moates]

Bill,

This is in Cadsoft Eagle 4.16 (www.cadsoft.de), it should fit in the 'Free' version but I haven't tried it that way.

Agreed on the 68HC58, it is obsolete. But I've got a few hundred laying around from another project so figured I'd try and make use 
of it. Plus you can still get it from sources like www.newark.com I think they have 700+ in stock at sub $4 each. Eventually it'll 
dry up in terms of supply, and the design will need to be updated.

Are there any updated chipsets which would handle all the VPW timing and encoding including 4x? I've seen the line level stuff like 
the MC33990, but you have to do all the pulewidth management at the micro side. I think that would be a great way to go, but would 
put more burden on the firmware development side. Maybe eventually, but for a quick-hit, the 68HC58 should cut it. Open to other 
ideas though.

Best regards,
Craig Moates


----- Original Message ----- 
From: "Bill Shaw" <b.shaw at comcast.net>
To: <gmecm at diy-efi.org>
Sent: Thursday, December 21, 2006 7:32 AM
Subject: Re: [Gmecm] Any USB developers out there?


> Hi Craig,
>
> What schematic capture are you using for this?  The first problem I see is the 68hc58,  Freescale says it's obsolete and not 
> recommended for new designs.
>
> Best,
>
> Bill
>
> Craig Moates wrote:
>> 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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