[Gmecm] Any USB developers out there?

Wed Dec 27 18:00:08 UTC 2006

Craig,

I have used an Alpha-Metals solder with a water soluble flux core, available through Digi-Key (www.digikey.com) I think.  Any reason you jumped directly to 0402 components from 1206 (or 0805)?  I have found I can squeeze most designs, with the exception of high-complexity small space boards like cell phones, using 0603 parts; though I haven't looked at your scematic or layout yet to see how tight a fit everything is.

Cheers
Dave

----- Original Message -----
From: Craig Moates <craig.moates at cox.net>
Date: Wednesday, December 27, 2006 10:23 am
Subject: Re: [Gmecm] Any USB developers out there?

> 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 
> anyoneelse), 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 
> housesget 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
> > [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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