Re: gEDA-user: Ok, who moved pin 4?

[Greg Cunningham <greg@xxxxxxxxxxxxxxxxxxxx>]

On Mon, 2007-11-26 at 02:51 -0500, DJ Delorie wrote:
> Spent the day building two r8c-based boards, thought I'd give a quick
> status, since I did some new things with this.
> 
> First off, I've got a board that has a USB chip (FTDI232R) connected
> to an R8C/20, connected to a bunch of headers.  In other words, it's a
> programmable USB GPIO port.  The only design flaw so far is that the
> mini-B connector has an extra pin, and ground is on pin 5 instead of
> pin 4 like all other USB connectors.  Fortunately, pin 4 is not
> connected on the device end, so I just shorted pins 4 and 5, and it
> worked just fine.  Haven't talked with the R8C yet, I need to adapt my
> R8C programmer to the FTDI driver.  This board also used the global
> puller, as I was able to coerce it to give me useful results.
> 
> Second, I've got an R8C/27 (TQFP-32) adapter (files are at
> http://www.delorie.com/pcb/r8c-27-adapter/).  Along with being a TQFP

The closing bracket breaks Evolution's auto-hyperlink thingy (tech-talk
for software)
-- 
Greg

> to DIP converter, it includes some pullups and the oscillator, so
> aside from programming you shouldn't need any support parts.  This
> board takes advantage of the ability to rotate parts 45 degrees.
> 
> Now, for the new things...
> 
> The DIP adapter is a two-layer board.  However, I did it using two
> separate SS boards, taped together.  This lets me line up the two
> etched boards after etching, instead of before etching.  The clad is
> 16 mil (1/64") with 1 oz copper, resulting in a 36 mil board.  The
> tape is 3M 7953 laminate adhesive, about 4 mil thick.
> 
> The USB board is a home-etched four layer board.  Yes, four.  The core
> is a 32 mil DS board, where I lined up the resist before etching.
> What I did here is iron on one side, drill out the alignment holes,
> and use those to line up the resist for the other side.  This core
> held the ground and power planes.  Then I taped the outer layers to
> it.  Those were 8 mil 1/2oz SS, and are pretty much transparent, so
> easy to line up and tape on.
> 
> The tricky part is the vias.  What I ended up doing is drilling big
> holes in the outer layers before taping them on, then drilling small
> holes through the full stack.  That left some of the inner layer
> copper exposed through the holes in the outer layers.  For signal
> vias, I only did the small holes, like a 2 layer board.  If I do more
> of these, I'm going to have to add some support to PCB for it, because
> I mis-drilled a lot of the holes.  For example, to connect a top
> signal (layer 1) to power (layer 3), I had to drill a big (35-45 mil)
> hole in layer 4, and no hole in layer 1, then a 14 mil hole through
> the stack.  To connect it to ground instead, I drill a 22 mil hole in
> layer one and no other holes.  To connect both sides to an inner layer
> means drilling a 22, a 25, and a 14 mil hole.  Plus, it would have
> gone better if I could have had different size copper (or no copper)
> on different layers based on connectivity.
> 
> I had to print each layer separately, because PCB wouldn't let me
> paste two boards into one layout and flip one, which would have let me
> etch both sides on one board then cut them apart and tape them
> together.
> 
> I also tried using glossy magazine paper instead of my usual coated TT
> paper.  I wanted to use some of my 64 mil (1/16") clad that won't fit
> through the laminator, too, so I ended up ironing it on.  The paper
> rubbed off like "they" said, but I was back to the original problem of
> getting the toner to stick completely, without getting so hot it
> smears.  I think the paper might work in the laminator though, and I
> have more clad than coated paper at the moment.
> 
> 
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