Let's think about hardware for a minute:

I assume youa re not going to build more than one of these.  Neither am I.
 Therefore the hardware does not have to be absolutely cheap, in fact if
it is easier to produce that is better.  If the whole cost of parts is
under a hundred clams then the Misses won't scream about it.

Power the thing with a 12 or 18V DC wall wart, and add a 5V regulator and
the power supply is done.

I am assuming that any 20MHz PIC will probably do the job, as long as it
has timer2 and enough pins.  I usually prototype with something out of the
16F87x series, since they have all the mid range peripherals.  16F873,
perhaps, would be plenty of overkill.  Crystal frequency is still a design
issue, IMHO

A serial LCD screen is hard to beat for a quick and dirty interface.  You
just write to it with an RS232 port.  Scott Edwards  BPI216N is a simple
unit that fills the bill  http://www.seetron.com/prices.htm#BPK216  $45.

If you are a real cheapskate then a Hantronics display can be had for $7
or $8, however wyou have to talk to it in Hitachi, which is a barrier
AFAIK. I would rather design something that takes minimum head-scratching.


Generally I would prefer to code something like this in C.  CCS or Hitech
either one is OK, CCS would be easiest to get up and running, since it has
the serial INVERT mode that saves messing about with a MAX232 serial level
converter.  If you are using a software UART this works, if you use a
hardware UART then a MAX232 is definitely required.

and of course, the speaker.  A large diameter piezo make sense, but it
will never sound that great being a cheap speaker.  That may be all we
need though.  Tie it to 18V across a resistor, power it with a 2N2222A
common emitter, and run the base to the PIC through a 1K resistor.  That
is the simplest sound output you can find, and will work fine for simple
sounds.  We are not playing MP3's here you know.

Any of this make sense?


-- Lawrence Lile





Koen van Leeuwen <koen@VANLEEUWEN.XS4ALL.NL>
Sent by: pic microcontroller discussion list <PICLIST@MITVMA.MIT.EDU>
01/07/2004 12:27 PM
Please respond to pic microcontroller discussion list


        To:     PICLIST@MITVMA.MIT.EDU
        cc:
        Subject:        Re: [PIC:] Frequency dividing to 440 Hz


On Wednesday 07 January 2004 18:24, you wrote:
> Yeah, these things can be bought cheap, the point is to have fun
improving
> it! (as you well know)
>
>
> -- Lawrence Lile

uhm, as a side note, the thing I intend to build is primarily a metronome
and
has the tuning feature as an improvement :o)
Of course, it would be interesting to add a freqmixer and a
freq-to-voltage
converter to do some neat "the BPM is 130 and your piano is 4.52 Hz wrong"
(and with a DTMF chip "should I call the piano tuner yes/no" or with a
modified accu drill, directly adjust the snares ) but that's not what I
originally intended. Heck, I dont even have a piano.
But I would like to have an accurate reference frequency...

Thanks for thinking, all.

Koen

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