Re: [avr-gcc-list] programming header, pinout?

[Richard Urwin]

On Tuesday 14 Dec 2004 2:27 pm, Graham Davies wrote:
> I wonder at what operating frequency and cable length the interleaved
> grounds become significant?  If I had to waste some wires, I'd
> interleave grounds on them too, but I'm not sure one should shy away
> from the more compact 6-pin layout just to get them.

The PC printer port has interleaved grounds, and a maximum specified 
cable length of 2 metres. It seems to me that the frequencies are 
probably comparable, so if you're in that order of length then they 
would be a good idea. Six inch cables probably don't need them, I'd get 
worried around 12-18 inches.

> Polarized / non-polarised / headers / sockets / whatever, 10-pin are
> easier to find (in small quantity at least) than 6-pin.  The same for
> the cable itself.  Neither Mouser nor Digi-Key have the 6-pin stuff.

I got mine from Farnell (.co.uk).

>
> "Richard Urwin" wrote:
> > NB. The pinout has pins 1 and 2 across the width of the pinout, and
> > odd numbers down one side and even numbers down the other. IIRC
> > that's not the standard numbering for IDC sockets, but it does
> > match the ribbon cable.
>
> This zig-zag numbering is standard for two-row headers, probably
> because of their common use with ribbon cable.  Mating IDC sockets
> only have pin 1 marked, so how the other pins are numbered is up to
> you.  Where you can get really confused is with IDC DB9s where the
> pins are numbered along one row first and then along the other.  Only
> pin 1 matches up end-to-end.

If you're only doing cables, yes. If you're designing PCB's it can catch 
you out if you put down an IDC socket rather than a pin header, for 
example to get the real-estate and silk screen correct.

> (Is this the most off-topic thing to 
> appear here, or what?)

(Probably :-)

-- 
Richard Urwin