I need to use a microcontroller, microprocessor, or some other IC to
receive binary or hexidecimal data from a computer to light up any
possible combination of 48 LEDs.  For example, a possible option would
be to use a BASIC Stamp to process the data and route the power to the
correct LEDs.  However, this would most likely be more complicated
than it has to be.  There must be an IC or microcontroller/processor
that is devoted to doing this kinda of task.

What are some possibilities of completing this task, approximately how
much does each cost, and how difficult would it be to implement?  I am
an undergraduate in Electrical Engineering, so I have some knowledge
in the subject, leading to an easier time understanding and
implementing the asnwer.  A wide variety of answers
is possible because I have not decided on a specific technology (i.e.
using logic as opposed to a microprocessor) or a specific transmission
method from the computer to the controller.

Thanks!

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Request for Question Clarification by endo-ga on 27 May 2003 18:21 PDT

Hi,

One possible solution would involve a 64 pin PIC, a programmer that
you could either borrow from your school, build or buy. Then you can
send the data to the PIC serially from the PC using 2 wires (ground
and data). You can then use a max233 chip to convert from RS232 to
TTL. I can tell you how to get the max233 and the PIC for free if you
live in the USA, but you would need to find a programmer and have a
compiler that you are comfortable with using.

Please let me know what you think.
Thanks.

---

Clarification of Question by mikerlester-ga on 28 May 2003 08:14 PDT

I do live in the US and do want to know how to get the max233 and PIC
for free.  That method was a possible solution that I was thinking of.
 Also, there is a good chance that I can find the programmer and
compiler at school.  If not, do you know where I could find/buy them? 
I'm sure between myself, other people here, and instructions, we can
figure it out.  Let me know if you need any other clarification.

Thanks
Mike

---

Request for Question Clarification by endo-ga on 28 May 2003 16:08 PDT

Hi,

Would you consider it an acceptable answer if I provided you with a
way to get the PIC and the MAX233 for free, and a programmer for
either $60 or $99, but you would need to find a compiler yourself,
sort out the connection to the LEDs and write the code yourself.

Please let me know what you think.
Thanks.

---

Clarification of Question by mikerlester-ga on 31 May 2003 13:04 PDT

That answer would be acceptable.  Let me know what you've found.  I
would aprreciate any quick hints, tips, or tricks with the MAX233/TTL
also, but it's not necessary.

Thanks
Mike

Hi,

To get the max233 go to
http://www.maxim-ic.com/samplescart.cfm?Action=Step1 and under enter
part number put "max233". Then do complete order, and fill out the
rest of the forms as they ask.
You can find the datasheet here:
http://pdfserv.maxim-ic.com/arpdf/MAX220-MAX249.pdf

You can use the max233 to convert the RS232 signals from your PC's
serial port into the TTL signals that the PIC will expect. From there
on, it will be a matter of programming the PIC to read the serial
data.

For the free PICs, go to http://sample.microchip.com/ . You need to
register, and then log in. Under sample item search go to PIC micro
Microcontrollers. Then choose PIC18F8620, or PIC18F8720 . Both those
chips will have more than enough pins for you to play with! Then you
just need to click 'add' next to e.g. PIC18F8720-I/PT . By doing this
a few times you can sample 5 different types of microcontrollers, and
get up to 3 of each for a total of 15 free PICs. :)

You can try this programmer
http://www.newfoundelectronics.com/warp-13a.htm but a cheaper
alternative could be http://www.didya.com/PicProg.asp

You can then have a look here:
http://www.diyha.co.uk/electronics/comm1.html 
For the PC's serial port you will only need to use two pins for this
project: pin 5 for ground, and pin 3 for transmit.

Check page 21 of this spec sheet for the max233 connections
http://pdfserv.maxim-ic.com/arpdf/MAX220-MAX249.pdf
 
As you can see, you connect pins 6/9 to ground and pin 7 to a+5v
supply. From my experience, using a molex connector from your PC's
power supply provides a very convenient power supply for the max233.

Now just connect the transmit pin from the serial port to pin 4 on the
max233, and on pin 3 you will see the TTL out. Also if things aren't
working as expected you might want to jumper pins 11&15, 16&10, 12&17
as suggested on the datasheet.

The 64+ pin PICs come in a package that will make programming
difficult.
i.e. You can't just drop the PIC into the ZIF socket of the
programmer.
You will need to use the ICP (in circuit programming) header, and need
to do some soldering to program it. The PIC's datasheet will contain a
section about ICP and will help you find the relevant pins to connect.
With the warp-13 it's very easy, just five connections to make and the
header's pins are clearly labeled Vdd, RB7, RB6 etc.

I highly recommend CCS PCWH compiler, but it costs hundreds of
dollars, unless your school can give you a license.

Hope you can work it all out, if you need any more information please
don't hesitate to ask.

Kind regards,

endo


I got most of the information from my cousin who has some experience
with this particular domain.

Search strategy:

max233 serial
://www.google.com/search?q=max233%20serial

PIC programming
://www.google.com/search?hl=en&lr=&ie=ISO-8859-1&newwindow=1&safe=off&q=pic+programming

PIC programmer
://www.google.com/search?hl=en&lr=&ie=ISO-8859-1&newwindow=1&safe=off&q=pic+programmer

Thanks for the great rating and the tip, if you need any more help let
me know, and I hope you'll be using Google Answers again. :)