Hi All (especially John, Dave, Eric & any other LCD enthusiasts)
first off,
please feel free to tell me to [insert favorite euphemism for consume
feces and cease to exist here] because i lack the expertise and the
time to pitch in on this suggestion in any substantive way....
it's a fair cop...
but here goes
i've been trying to digest all the discussion about the LCD
implementation and my (so-called) mind wandered into the question of
using this gadget not only as a display but as part of an INPUT scheme
for user interaction as well.
(yes! i know i've always been sort of indifferent to the LCD before
and so i have to wear the 'hypocrite hat' for 24 hours too!)
------------
but considering the following two design ideas:
a separate (Samsung? Hitachi?) microcontroller residing on a separate
PCB with the LCD
and
a fairly flexible and open-ended interface, specifically: piggybacking
display data traffic on MIDI sysex
(which strikes me as cleverer every time i think about it... kudos Dave!)
-------
Is it feasible and practical to consider the addition of a few (maybe
5) buttons to interact with the display via cursor? (up down left
right enter)
and THUS transmit some data to the main CSV processor (ie program
selection parameter select etc.) via sysex
Now as i have already expressed my readiness to be openly ridiculed
for broaching such a can of worms. Let me say that i have a little
experience with the software side of interpreting 'Keyhole' interfaces
and i realize that as a user interface, they are far from luxurious
(ala the DX7 or the Mirage)
i also realize that we'd have to "OR" into the RXD pin on the Main
processor but that doesn't 'SEEM' to intrusive to my unschooled eye.
so i'll shut up about this now
and leave this notion to those better able to judge it's merits than
myself
a tip of the hat to all for keeping this barn-raising in motion,
-doc
--- In
ComputerVoltageSources@yahoogroups.com, "djbrow54" <davebr@...>
wrote:
>
> A couple of thoughts. First, the LCD microcontroller should be on
> the same PCB as the display. This allows changes to support a
> variety of displays and interfaces.
>
> The MIDI out signal is generated via two resistors so there's not a
> lot of circuitry involved. Monitoring the TTL signal is appropriate.
>
> There are two options here: simply monitor the MIDI out signal or
> loop it through the microcontroller.
>
> Advantages of looping it through the microcontroller is that you can
> actually filter out the display sysex messages and not send them
> out. Since they are sysex messages it shouldn't matter but you
> always have the opportunity to add or expand the protocol since you
> can filter the messages out. Right now I'm using the educational
> ID. I suppose that is OK since this is a non-commercial
> application. It doesn't really matter, though since the messages
> are never passed through to MIDI out.
>
> Disadvantages are that it adds a 1 or 2 byte delay to the message.
> Pretty minimal.
>
> One possibility would be to loop through the TTL signal at the
> connector (e.g. put a jumper on the connector). This allows MIDI to
> work without a display but when a display is connected, it filters
> out the display messages. It can still be done with a 4 pin
> connector.
>
> 6 of one, half dozen of the other ...
>
> Dave
>
> --- In ComputerVoltageSources@yahoogroups.com, "Grant Richter"
> <grichter@> wrote:
> >
> > A complete MIDI interface will be on the main board.
> > As I understand it, the LCD display microcontroller monitors the
> > MIDI data stream looking for a SYSEX string.
> >
> > My thought was to simply send the 5 volt level TXD pin to the
> > external LCD board. Not the current loop signal.
> >
> > That would eliminate any need for level shifting or an opto
> > isolator on the display sub assembly.
> >
> > It would also allow the display to mounted in many more mechanical
> > positions if seperate from the main board, and with it's own power
> > supply.
> >
> > It would also be possible to have different size displays, or
> > multiple displays each with a unique SYSEX code.
> >
>