[Gmecm] Any USB developers out there?

[Craig Moates]

Hi Steve,

Here's a link to DB9 cables:
http://www.obd2cables.com/products/
Cheapest I could find around, sub-$10 in bulk, sub-$20 even individually.

My wife and I do the 0402 all the time by hand (she doesn't like them!), it's not bad at all but it definitely takes some getting 
used to. Of course if you drop one, might as well forget about it and grab another. Just use magnifying head gear, 0.015" organic 
core solder, tweezers, and a fine tip. Regarding paste, I've used it with hot air and not had the best of luck. Little balls tend to 
float around and up under stuff (was trying to do a TQFP144 package that way). Had a lot better luck just laying it down normally 
and coming back with the wick as needed. Not sure about the aging, but I gave up on it. I suppose it's fine for volume production 
using stencils and pick-n-place.

By the way, anyone know of a water-soluble fluxed wick that works well? The stuff I use works OK, but leaves solvent-needy residues 
instead of full water clean. I'd like to have some better wicking material.

Yes, you can supply a good 100mA or so from just about any USB bus. Fairly decent power supply, not too noisy.

I did cross-check the board dimensions compared to the recommended PCB size for the Pactec enclosure, and I have some of them in 
hand. Appears to be correct, but they'll need to be trimmed pretty closely to actually fit. Also, the hole for the USB side is 
actually for an RJ11, so it'll be slightly too big. I've seen where some folks have used a rubber O-ring around the USB connector to 
center that end of the assembly in the enclosure, that works well. But the USB side of the board might need to be set back slightly 
to allow for that placement.

I'll see about setting something initial up in C then. Been trying to force myself more in that direction on new projects. Gives a 
lot more flexibility and portability.

For PCBs, if you've got anything you want run, just let me know. I can saddleback what you've got into one of my submissions. I try 
to put some 'known good' stuff in with the proto projects so that it isn't a waste if it doesn't work out. I put in 60 square inches 
of various prototypes to www.4pcb.com at least every 2 weeks under their www.33each.com offer. For the arrays, you can squeeze a lot 
of stuff into 60 square inches (their limit) and get 3 boards (their minimum) for $99 plus $50 (their upcharge for step/repeat/array 
characteristics). Lead time is 5-7 business days. Not a bad deal. There's some other deals out there, but I've had good luck with 
these guys. As long as you keep your spacing wider than 8 mils or so, and use traces of 8 mils or better and vias of 12 mils or 
better you should be OK. I usually go with 10 mil spacing, 10 mil trace width, and 16 mil via mininums.

Best regards,
Craig Moates


----- Original Message ----- 
From: "Steve Ravet" <Steve.Ravet at arm.com>
To: <gmecm at diy-efi.org>
Sent: Wednesday, December 27, 2006 1:14 AM
Subject: RE: [Gmecm] Any USB developers out there?


Hey Craig, thanks for sharing.  I have a few questions:

Is the 9 pin to OBD2 cable something that is standard or one of your
cables?  I used a DB-15 on mine, but was planning on moving to a DB-25
to allow more of the PIC pins to be pinned out (ie misc analog and
digital I/O).  But if the DB9 is standard I may switch to it.

I guess you use solder paste to do 0402?  In your experience (or anyone
else), does solder paste really go bad within a month?

After looking at yours I realized there's no reason to have the 5V
regulator in there, might as well always have the VCC stuff powered from
USB.  Eliminates parts and makes the BOM that much cheaper.  I'm also
going to use your board layout to fit the Pactec enclosure.

I'm writing my firmware in C, since microchip assembly makes my head
hurt.  As far as the host interface, I had planned on implementing the
SAE J2534-1 API.  (Yes, this is an SAE spec that specifies a windows
API).  This is a standard API for vehicle reprogramming but the API is
generic enough to work for normal scan tool operations also.  The spec
requires support for all vehicle protocols but USBVPW will only do VPW.
That SAE spec is now on the USBVPW wiki page, take a look.

What do you think your BOM cost is, including the PCB?

Speaking of PCBs, I have a number of small (couple square inches or
less) projects I've been wanting to do but it seems like most PCB houses
get offended if you do arrayed PCBs.  Is there a PCB place that will do
a 4x6 PCB with many individual circuits on it and not want to give me
all kinds of per project charges?  Otherwise the cost for these one-offs
is prohibitive.

--steve

> -----Original Message-----
> From: gmecm-bounces at diy-efi.org
> [mailto:gmecm-bounces at diy-efi.org] On Behalf Of Craig Moates
> Sent: Monday, December 25, 2006 3:01 PM
> To: gmecm at diy-efi.org
> Subject: Re: [Gmecm] Any USB developers out there?
>
> Folks,
>
> I updated the layout, and it's probably ready for a proto
> run. Check it out if you like:
> www.moates.net/projects/
> Got tired of trying to squeeze those beefy 1206s in there so
> went to mostly 0402. They're doable with magnifier and tweezers.
>
> All the components are specified, laid out pretty well, and
> labeled on the schematic and silkscreen.
>
> I'll start working on the firmware shortly. Prefer C++ or
> ASM? Guess I'll make it compatible with some of the 'other'
> stuff out there.
>
> Best regards,
> Craig Moates
>
>
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