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[Lcdproc] JW-002 (8x24 LCD) driver in the works


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  • From: ethan.dicks AT gmail.com (Ethan Dicks)
  • Subject: [Lcdproc] JW-002 (8x24 LCD) driver in the works
  • Date: Mon Apr 28 04:51:01 2008

Hi, All,

After having a JW-002 serial display lying around for a number of
years, I finally
got a level-shifter/Vee board built for it, and have started on a driver.

The display has been available through surplus LCD sellers for some time, but
the native firmware is rather stupid. Fortunately, in the process of making
the
display more useful for his MP3 player, Paul Stoffregen at pjrc.com has
written
new firmware and released it into the public domain. He also sells displays
with a 12-button pushbutton board that includes the RS-232 level shifter and
Vee supply, so all you'd need is a source of +5VDC and a (DE9) serial cable
(I made a special cable that grabs +5VDC from a nearby USB port, but there
are other ways of doing it).

After a night's hacking, I have a preliminary driver that supports basic
screen
handling and refresh, plus horizontal and vertical bargraphs, and custom chars
including bignums. The only major feature I have left to implement is keypad
input (via 7 built-in I/O lines that are already set up for a 4x3 matrix scan
in
Paul's replacement firmware). I'm currently doing bargraphs and bignums
through brute-force (using custom chars the way it's done for a MatrixOrbital
display), but since the replacement firmware has rich font support (four
built-in ROM fonts by default, plus room for a lot more if you compile your
own firmware from source), I might hold back on a release until I get
bargraphs,
at least, working with the the native fonts, since it spares the LCDd
server from
a lot of serial traffic not to have to redefine chars that are already
available
in ROM.

Anyone who has gotten one of these displays from a surplus vendor in the
past will need to either burn their own 512Kbit/1Mbit EEPROM or buy one
from Paul. The display is used in a popular MP3 player project, so even
though the JW-002 isn't as common as, say, Matrix Orbital displays, I found
the lure of an enourmous 2"x4" 8x24 screen too tempting not to add support.

Once I get keypad support and documentation written up, I'll be submitting
the driver, but I was excited enough about getting it working with the basics
to want to shout it out on the list.

It does bring me to another point... LCDproc support of
less-that-fully-commercially-supported-displays.
By this I mean devices that do _not_ directly and easily interface to a
computer as sold, and that have "how to interface this" pages that may
or may not be around a few years from now. The PJRC pages for the JW-002
go back to, IIRC, 2001, and are still around. One set of pages that the
LCDproc
page points to that is *not* around, however, is the stuff at
http://www.lcdproc.org/docs.php3
(as pointed to by the Hardware page - http://www.lcdproc.org/hardware.php3).

Fortunately, I was able to locate (on archive.org) 99% of what I need to get
my SED1520 display attached to a PC parallel port, but I don't know if most
folks are that tenacious about trying to get a $5 surplus display working.
The experience does make me wonder if we should be preserving this sort
of information directly. I'm sure most folks who are willing to put up pages
describing what they went through to get a particular display to work wouldn't
mind having another site host an "off-site copy" of their efforts (with full
and proper attribution, of course). For some projects, it might only be PNGs
of the interface schematics; for others, schematics and microcontroller
firmware. It then comes down to how to organize it on the LCDproc
webpages, but if we don't do it for displays that have "some assembly
required", we risk providing software support for displays that might no
longer
be possible to easily attach, especially for less experienced users.

So how does the idea of a "you-build-it" schematic-and-firmware page as
part of the LCDproc pages sound?

JW-002 Related links:
http://www.pjrc.com/tech/mp3/pushbutton_info.html
http://www.pjrc.com/mp3/lcd_protocol.html

-ethan




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