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From: Tomás Ó hÉilidhe on 6 May 2008 17:57
On May 6, 9:11 pm, linnix <m...(a)linnix.info-for.us> wrote:

> You keep avoiding the question:
> What wrong with using 13 pins?
> There are tons of uC with more than 13 pins.


Well they only microcontroller I've ever worked with is the PIC16F684,
and it has 12 pins to play with. That's the only reason. I'm new to
embedded systems so I don't have much clue about what microcontroller
to pick for the job.
From: Tomás Ó hÉilidhe on 6 May 2008 18:00
On May 6, 8:30 pm, "John Speth" <johnsp...(a)yahoo.com> wrote:
> > 1) Should we worry about "noise" and "static", or should we rely on
> > the chips doing their job perfectly?
>
> I've a question for you: When was the last time anything was perfect?


The PC I'm typing on right now is perfect. It's working exactly as
intended. When I press "e", an "e" appears on the screen. Even if I
press "e" one million times I'll still only ever get an "e". That's
perfect.


> The question is your How much imperfection can you tolerate?


Well if something could go wrong *inside* my microcontroller then I'm
f**ked. If a register changes from 100 to 110 then the whole program
will behave erratically, perhaps even setting pin values that will
result in a short circuit that will burn out components.

If something can only go wrong on the pins *outside* of the chips,
then I suppose it isn't too bad if my LED matrix has a dodgy flash
once every couple of weeks. It'd be a bit much though if it happened
once every minute.
From: Tomás Ó hÉilidhe on 6 May 2008 18:02
On May 6, 8:18 pm, Arlet Ottens <usene...(a)c-scape.nl> wrote:

> Some other things that could upset the state, that you might not have tried:
>
> - Wiggle the power connector such that the power is briefly interrupted.
>
> - Zap the exposed parts with some static electricity. You can charge
> yourself on a carpet. For best effect, hold some metal object like a
> screwdriver, and tap your device with it.
>
> - Plug some heavy duty electrical equipment into an outlet on the same
> strip, and quickly power cycle it, or wiggle the prongs in the outlet.
>
> - Put your cell phone near the device, and call it


Will all of these things only result in erratic behaviour on the
*outside* of the chips, i.e. on the pins. If it were to result in
erratic behaviour *inside* the chip, then what hope have we? I mean if
a register's value gets changed then the program will go haywire.
From: Jim Granville on 7 May 2008 06:55
Tom�s � h�ilidhe wrote:
> On May 6, 10:21 pm, Electroniker <no...(a)wrenchman.com> wrote:
>
>
>>You can still use the one pin method and have "zap proof" recovery.
>>You can shift out enough zero data to ensure that all LEDs have been
>>cleared and then shift out your desired pattern. You control the 1's.
>
>
>
> Please show me how you'd do this using only one microcontroller pin.

Some reading on 1 wire BUS systems :

http://en.wikipedia.org/wiki/1-Wire

and a new one, the Uni/O
http://ww1.microchip.com/downloads/en/DeviceDoc/DS-22076B.pdf

LIN bus is another 1 pin IO standard.

and, there are bus designs that use the 3 state's of a typical
uC port, as another encoding system. Low, Light Hi, for CLK,
and Hard-Hi for RST.

-jg


From: CBFalconer on 7 May 2008 11:32
Tom�s � h�ilidhe wrote:
> Electroniker <no...(a)wrenchman.com> wrote:
>
>> You can still use the one pin method and have "zap proof"
>> recovery. You can shift out enough zero data to ensure that all
>> LEDs have been cleared and then shift out your desired pattern.
>> You control the 1's.
>
> Please show me how you'd do this using only one microcontroller
> pin.

For a simple example, ship UART codes (10 sequential bits)
producing 8 bits. Use 3 to control position (i.e. which LED block)
and 5 to control the bits. No persistent errors. Rep. rate
depends on UART speed.

--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: <http://cbfalconer.home.att.net>
Try the download section.


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