Todd Pattist wrote:
> Here's my first project:  My wife has an espresso machine and she wants
> a timer to turn it on in the morning.  It uses rubber pad switches to
> turn on/off.  Holding the switch pad down for 4 seconds turns it on (if
> it's off - otherwise it enters programming mode).  Holding it down for 2
> seconds turns it off (if it's on - otherwise it does nothing.)

Wow, that has got to be one of the worst user interface I've ever heard of.

> The
> voltage on the on/off switch pad is 5 volts on side 1 and ground on the
> other side.  About 0.5 ma flows when the switch is closed.

Good.  This means you can put a NPN transistor in parallel with the switch.

> I've looked at the Microchip App Note AN582 Low-Power Real-Time Clock
> that uses an Hitachi 2 x 20 LCD display.  If  I use the same, I figure
> I'll need 7 outputs for the display, and 4 switch inputs (select units
> to change, increment units, zero seconds reset and select
> clock/on_time/off_time display), and it looks like MCLR is used for a
> master reset.  I have some assembler programming experience, and I've
> studied a few PIC listings.  I know I'll need to try some "hello world"
> basics before building this, but I'd appreciate some comments:
>
> What chip might be good to select for this ultimate design?  Something
> with lots of sample programs on the web I can look at would be good.

Just about any PIC will do here.  It seems you're only asking for about 12
I/O lines.  However, you won't want to buy just one PIC and they are cheaper
if you buy a handful, so I suggest a PIC that will be good for other
projects too.  It sounds like a PIC in the standard 18 pin footprint will be
fine.  In that case I would go for the 16F648A or 16F88 as these are the
biggest bestest in the 16 family with 18 pins.

> Not too expensive, for when I screw up.

That actual PIC price will be relatively little compared to all the other
project costs.

> Can you suggest a programmer.

You should be thinking about how you're going to debug this.  For that the
ICD2 is the best answer as it's a programmer too.

> I've seen something called the No Parts
> Programmer, that uses a parallel port running under DOS.

All those "no parts", "El Flako", and other programmers without a controller
are going to be frustrating, especially when things don't work right and you
don't have the experience to take a good guess at which of the 20 possible
reasons it is.

If you really want just a programmer, consider my EasyProg
(http://www.embedinc.com/products) or Wouter's Wisp.

> I've got an older UV
> eraser and EPROM programmer that I can at least scavenge the 40 pin ZIF
> from.

Other than that, maybe a museum would want it.


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