[Arm-netbook] Early UART output vs. housing board discovery

[Jonathan Neuschäfer]

Thanks for your explanations. That's all I really have to say after that
mail.


On Fri, Jan 12, 2018 at 10:29:14AM +0000, Luke Kenneth Casson Leighton wrote:
[...]
> > * If the CPU card spontaneously resets without first bringing the
> >   housing into a state where it tolerates early debug output
> >   (some housings might require such preparation before shutdown).
> 
>  exactly.  and that is far too complicated.  right now there is *zero*
> need - at all - for *any* kind of complexity on the Housings.  the
> Micro-Desktop is.... it's just a bunch of connectors.  as in, that's
> *all* that's needed.

I wasn't aware housings tend to be *this* simple.

> > Here's a *completely different* and significantly simpler proposal,
> > which also fulfills these goals. You probably won't like it because
> > (a) it takes away a pin from general purpose use, (b) it breaks
> > compatibility [see footnote 1] with current hardware.
> >
> >   Replace one of the GPIO pins (such as pin 21, GPIO 20) with a single-
> >   purpose Debug UART TX pin, where the CPU card may print debug messages
> >   in 8N1 format. Debug UART TX high/low is measured against VREFTTL.
> 
>  nope.  not enough pins.  you're thinking in terms of prioritising
> "Technical End-User" over "End-User".
> 
>  the volume of sales to "End User" is intended to be HUNDREDS OF MILLIONS.
> 
>  the volume of sales to "Technical End User" is expected to measure in
> the thousands.

Ok, makes sense. That's a valid design point.


Thanks,
Jonathan Neuschäfer