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PICList Thread
'PIC or SBC?'
1997\09\18@150542 by Steven J Tucker

flavicon
face
Hello,

       I recently did a few projects w/ the 16c84 from Microchip, and I
want to use a PIC to interface an AT keyboard to a computer that uses a
8x8 matrix keyboard.   To do it I need at least 7 i/o lines for the matrix,
2 for the AT keyboard, and enough accessable ram/eprom for a lookup
table to translate the AT scancodes to the 8x8 matrix.

       I also need some RAM to store the make/break state of the keys, not
alot but enough to buffer keystrokes as they come in, and remove them
when lifted.

       What microcontroller should I use?  It would be possible w/ a
10mhz 16c84 if it had enough EEDATA to store the lookup table, since its
limited SRAM is probably enough for the buffer.  Is there any way to read
the program ee area from within the program?  That might make it possible.

       Are there any other PIC's I might consider?   The only one I have
ever done any projects with so far is the 16c84.

Thanks :)

Steve

   * * *  Author of Imagic and APE - The Atari Peripheral Emulator!  * * *
   * * *      Turn your 8-bit Atari into a powerhouse with APE!      * * *
  *  *  *        Ape Homepage: http://www.nacs.net/~classics        *  *  *
*    *    *********************************************************    *    *
!! Request my *FOR SALE* LISTING OF CLASSIC VIDEO GAME STUFF -- 2000+ Items !!

1997\09\18@153532 by Martin R. Green

picon face
The current issue of Steve Ciarcia's Circuit Cellar Ink magazine has a
project almost identical to what you are doing, except it converts PC
keyboard make and break codes into RS232.  It is physically tiny, and
designed to fit entirely in the DB9 shell.  Although not exactly what you
are doing, he covers the details of processing PC make/break and scan codes
in depth.

I don't have the issue here at the office, so I can't tell you what MCU he
used, but since this issue is current, you should be able to find it
locally.  The cover of the magazine has an old metal movie film cartridge
on it.  The one with the child's building blocks on it is last month's
issue.


HTH - Martin R. Green
spam_OUTelimarTakeThisOuTspambigfoot.com

PS. Here's the Circuit Cellar Ink URL:

  http://www.circuitcellar.com/public/cc/ink.html

PPS.  If you use a PIC, you don't need to EEPROM for the conversion tables,
you should be able to use RETLW ROM lookup tables instead.

----------
From:   Steven J Tucker[SMTP:.....classicsKILLspamspam@spam@NACS.NET]
Sent:   Thursday, September 18, 1997 2:59 PM
To:     PICLISTspamKILLspammitvma.mit.edu
Subject:        PIC or SBC?

Hello,

       I recently did a few projects w/ the 16c84 from Microchip, and I
want to use a PIC to interface an AT keyboard to a computer that uses a
8x8 matrix keyboard.   To do it I need at least 7 i/o lines for the
matrix,
2 for the AT keyboard, and enough accessable ram/eprom for a lookup
table to translate the AT scancodes to the 8x8 matrix.

       I also need some RAM to store the make/break state of the keys, not
alot but enough to buffer keystrokes as they come in, and remove them
when lifted.

       What microcontroller should I use?  It would be possible w/ a
10mhz 16c84 if it had enough EEDATA to store the lookup table, since its
limited SRAM is probably enough for the buffer.  Is there any way to read
the program ee area from within the program?  That might make it possible.

       Are there any other PIC's I might consider?   The only one I have
ever done any projects with so far is the 16c84.

Thanks :)

Steve

   * * *  Author of Imagic and APE - The Atari Peripheral Emulator!  * * *
   * * *      Turn your 8-bit Atari into a powerhouse with APE!      * * *
  *  *  *        Ape Homepage: http://www.nacs.net/~classics        *  *
*
*    *    *********************************************************    *
  *
!! Request my *FOR SALE* LISTING OF CLASSIC VIDEO GAME STUFF -- 2000+ Items
!!

1997\09\19@004214 by Steven J Tucker

flavicon
face
On Thu, 18 Sep 1997, Martin R. Green wrote:

> The current issue of Steve Ciarcia's Circuit Cellar Ink magazine has a
> project almost identical to what you are doing, except it converts PC

[snip]

Thanks for the info, I will look for it.

> PPS.  If you use a PIC, you don't need to EEPROM for the conversion tables,
> you should be able to use RETLW ROM lookup tables instead.

Can you point me to any examples of this?  I assume you mean a large
block of RETLW statements, w/ an indirect CALL somehow?  On a 6502 there
is an indirect JSR addressing mode, but on the pic?  I would really love
to see how this is done, seems very inventive :)

Steve

   * * *  Author of Imagic and APE - The Atari Peripheral Emulator!  * * *
   * * *      Turn your 8-bit Atari into a powerhouse with APE!      * * *
  *  *  *        Ape Homepage: http://www.nacs.net/~classics        *  *  *
*    *    *********************************************************    *    *
!! Request my *FOR SALE* LISTING OF CLASSIC VIDEO GAME STUFF -- 2000+ Items !!

1997\09\19@071658 by Steve Lawther

flavicon
face
    Steve,
   
    See my AT keyboard viewer code for a PIC16C84 - This takes codes from
    the keyboard, and using a look-up table in program ROM converts it to
    ASCII and words, to display on an LCD.
   
    http://ourworld.compuserve.com/homepages/steve_lawther/keybinfo.htm
   
    Also a load of links for more info.
   
               Steve Lawther


______________________________ Reply Separator _________________________________
Subject:      PIC or SBC?
Author:  MIME:.....classicsKILLspamspam.....NACS.NET at INTERNET-HUSKY
Date:    18/09/97 20:21

Hello,
   
       I recently did a few projects w/ the 16c84 from Microchip, and I
want to use a PIC to interface an AT keyboard to a computer that uses a
8x8 matrix keyboard.   To do it I need at least 7 i/o lines for the matrix,
2 for the AT keyboard, and enough accessable ram/eprom for a lookup
table to translate the AT scancodes to the 8x8 matrix.
   
       I also need some RAM to store the make/break state of the keys, not
alot but enough to buffer keystrokes as they come in, and remove them
when lifted.
   
       What microcontroller should I use?  It would be possible w/ a
10mhz 16c84 if it had enough EEDATA to store the lookup table, since its
limited SRAM is probably enough for the buffer.  Is there any way to read
the program ee area from within the program?  That might make it possible.
   
       Are there any other PIC's I might consider?   The only one I have
ever done any projects with so far is the 16c84.
   
    <snip>

1997\09\19@100648 by Martin R. Green

picon face
I know this is available on many PIC enthusiast sites, and it is also in an
app note on the Microchip site, but it is so simple that I'll state it
here.

Starting with the lookup value in W, call a lookup subroutine to get the
converted value, also in W.

convert:
   addwf PCL,1
   retlw val 1    ; W = 0
   retlw val 2    ; W = 1
   retlw val 3    ; W = 2
   retlw val 4    ; W = 3
   retlw val 5    ; W = 4
   ...
   retlw val n    ; W = n-1

Note that the entire lookup table must not cross a page boundary.  This all
depends on the unusual fact (compared to other MCU's) that the PIC program
counter can be manipulated like any other register by the addwf
instruction.


HTH - Martin R. Green
EraseMEelimarspam_OUTspamTakeThisOuTbigfoot.com


----------
From:   Steven J Tucker[SMTP:classicsspamspam_OUTNACS.NET]
Sent:   Friday, September 19, 1997 12:44 AM
To:     @spam@PICLISTKILLspamspammitvma.mit.edu
Subject:        Re: PIC or SBC?

On Thu, 18 Sep 1997, Martin R. Green wrote:

> The current issue of Steve Ciarcia's Circuit Cellar Ink magazine has a
> project almost identical to what you are doing, except it converts PC

[snip]

Thanks for the info, I will look for it.

> PPS.  If you use a PIC, you don't need to EEPROM for the conversion
tables,
> you should be able to use RETLW ROM lookup tables instead.

Can you point me to any examples of this?  I assume you mean a large
block of RETLW statements, w/ an indirect CALL somehow?  On a 6502 there
is an indirect JSR addressing mode, but on the pic?  I would really love
to see how this is done, seems very inventive :)

Steve

   * * *  Author of Imagic and APE - The Atari Peripheral Emulator!  * * *
   * * *      Turn your 8-bit Atari into a powerhouse with APE!      * * *
  *  *  *        Ape Homepage: http://www.nacs.net/~classics        *  *
*
*    *    *********************************************************    *
  *
!! Request my *FOR SALE* LISTING OF CLASSIC VIDEO GAME STUFF -- 2000+ Items
!!

1997\09\19@175212 by Eric van Es

flavicon
face
Martin R. Green wrote:

> Starting with the lookup value in W, call a lookup subroutine to get
> the
> converted value, also in W.
>
> convert:
>     addwf PCL,1
>     retlw val 1    ; W = 0
>     retlw val 2    ; W = 1
>     retlw val 3    ; W = 2
>     retlw val 4    ; W = 3
>     retlw val 5    ; W = 4
>     ...
>     retlw val n    ; W = n-1
>
> Note that the entire lookup table must not cross a page boundary.
> This all
> depends on the unusual fact (compared to other MCU's) that the PIC
> program

Some time ago I posted a mail that allowed you to cross the boundary....

Look in the archives, or ask me and I'll type it out again!

Cheers!

--
Eric van Es               | Cape Town, South Africa
KILLspamvanesKILLspamspamilink.nis.za | http://www.nis.za/~vanes
LOOKING FOR TEMPORARY / HOLIDAY ACCOMODATION?
http://www.nis.za/~vanes/accom.htm

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