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'[PIC] Select a chip and programmer for first proje'
2005\12\19@101603 by Todd Pattist

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face
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.)  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.  I'm guessing
the machine uses a microcontroller (to control temps, flow rates,
timing, etc.) , and I'm looking at a switch that has a 5 volt pullup
connected to an input to detect when the switch is pressed to drop it
low and for how long.

I can't easily get access to the microcontroller, but I can get to the
on/off switch.  Here's what I'd like to build - A separate PIC
microcontroller to turn on/off the espresso machine's on/off switch.  
The separate PIC microcontroller runs an LCD clock display with
pushbutton switches to set the clock time, a master reset switch and a
switch to cycle through displays of clock time, on time and off time.
When the on time arrives, the PIC sends a 2 second pulse to turn it off
(in case it's on) then a 4 second pulse to turn it on).  When the off
time arrives, it just sends the off time.  I don't have direct access to
5 volt power, so I think it will be battery powered.  If I can sneak 5
volt power off the machine, battery backup would be nice.

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.  
Not too expensive, for when I screw up.  Any sample code for clocks with
timer alarms would be helpful, there must be several of those.

Can you suggest a programmer.  I've seen something called the No Parts
Programmer, that uses a parallel port running under DOS.  I've got
various computers from Debian/Linux to W98 to WXP.  I've got an older UV
eraser and EPROM programmer that I can at least scavenge the 40 pin ZIF
from.  It might be nice to build something, but buying is OK if not too
expensive.

Is it likely I can scavenge an LCD display from an old clock/phone, or
will they be custom and need more inputs/outputs than I have.

Thanks for your comments.

2005\12\19@105309 by Alan B. Pearce

face picon face
>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 ...
>  I know I'll need to try some "hello world" basics
>before building this, but I'd appreciate some comments:

Haven't looked at the app note, but this sounds reasonable.

>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. Not too expensive, for when I screw up.
>Any sample code for clocks with timer alarms would be
>helpful, there must be several of those.

You do not say what chip the app note uses, but I would suggest that a
16F876 or 18F252 (or the later versions of it) would probably be the way to
go. Also note that you may be able to get some chips as samples from
Microchip.

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

A lot of people have problems with these for various reasons.

>I've got various computers from Debian/Linux to W98 to WXP.

Check out the programmers available from Olin
http://www.embedinc.com/easyprog/index.htm or Wouter
http://www.voti.nl/shop/catalog.html (look for Wisp628) which provide
extensive features for hobby use. These will save you a heap of potential
problems getting going, and allow you to be pretty certain that you have
programmed the chip correctly.

>I've got an older UV eraser and EPROM programmer that I can
>at least scavenge the 40 pin ZIF from.  It might be nice to
>build something, but buying is OK if not too expensive.

With the Flash memory parts you will not need a UV eraser, and the parts can
be programmed in circuit (with a little care in setting up the circuit).

>Is it likely I can scavenge an LCD display from an old
>clock/phone, or will they be custom and need more
>inputs/outputs than I have.

I have scavenged displays equivalent to the ones you mention are used in the
app note, from FAX machines. Any other item using a similar sort of display
is likely to be using these as well, although one does need to be a bit
careful with pin connections, as some end up being effectively back to front
because of the way the display PCB is laid out. If the display is a fully
graphic one it may also be useable if the controller is on a PCB that is
part of the display, as it is again likely to be a second source of a well
known chip.

2005\12\19@121650 by olin piclist

face picon face
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.

{Quote hidden}

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.


******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2005\12\19@165722 by Kevin

picon face
On Mon, 19 Dec 2005, Todd Pattist wrote:

{Quote hidden}

Do check out http://www.glitchbuster.com. His prices for single
chips are probably unbeatable, and his shipping and handling
is only $1.85.
Also, I believe he will burn a program in a chip for 20% of
the chip price. You could use the PIC16F88 bootloader from
http://www.sparkfun.com and get away with not buying a programmer
at all.  See Sparkfun tutorials for what a bootloader is.

Also, if you want a cheap programmer you can check out
sparkfun or http://www.phanderson.com, Peter Anderson also charges
very low S&H prices.

Have Fun,
Kevin

P.S. No affiliation to the above, just a satisfied customer.

2005\12\19@173549 by Mark Rages

face picon face
On 12/19/05, Todd Pattist <spam_OUTtpattistTakeThisOuTspamsnet.net> wrote:
>
> I can't easily get access to the microcontroller, but I can get to the
> on/off switch.  Here's what I'd like to build - A separate PIC
> microcontroller to turn on/off the espresso machine's on/off switch.
> The separate PIC microcontroller runs an LCD clock display with

Can you can figure out how to access the microcontroller?  Odds are
good that it's a PIC.  Replacing or reprogramming it would be in
interesting, elegant solution.  (But maybe not appropriate for a first
PIC project.)

Regards,
Mark
markrages@gmail
--
You think that it is a secret, but it never has been one.
 - fortune cookie

2005\12\19@184517 by Jinx

face picon face
part 1 1738 bytes content-type:text/plain; (decoded 7bit)

> time arrives, it just sends the off time.  I don't have direct access
> to 5 volt power, so I think it will be battery powered.  If I can
> sneak 5 volt power off the machine, battery backup would be
> nice

The machine may or may not have a transformer supply, which
would be the safest to use. If it doesn't, you can tap off whatever
it's using to power the micro or, less ideally, make your own

http://home.clear.net.nz/pages/joecolquitt/txlesspsu.gif

BE AWARE THAT WORKING WITH A CIRCUIT LIKE
THIS CAN BE DANGEROUS AND YOU SHOULD USE
AN ISOLATING TRANSFORMER

> Any sample code for clocks with timer alarms would be
> helpful, there must be several of those

Purely internal time-keeping is not too difficult. You just need
a few registers for hours, minutes, seconds and ticks (ie an IRQ
counter). Add a few more for output to a display. Any PIC will
have more than enough RAM for this. The source for IRQs can
be primarily mains cycles, which will be the most accurate, and
secondarily a 32kHz xtal on TMR1 for when mains power is off.
You'd want mains to be present most of the time, as plain xtals
do drift. Maxim/Philips have RTCs that are pretty stable. eg

http://www.maxim-ic.com/products/timers/real_time_clocks.cfm

but for this application you don't really need a calendar IC. See
the attached gif. It has most of the bits that you need. The PIC
monitors the "Vsense" line to know when mains is there. If it is,
then mains cycles (ticks) are counted. If it isn't, the 50Hz TMR1
IRQ takes over. The "ticks" counter counts down from d50 to d00,
at which point "seconds" is incremented, "ticks" is re-loaded with
d50, and so on


part 2 13563 bytes content-type:image/gif; (decode)


part 3 35 bytes content-type:text/plain; charset="us-ascii"
(decoded 7bit)

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