Archive of the former Yahoo!Groups mailing list: ComputerVoltageSources

Just spent some time on the phone with John Loffink discussing the
various display options. To summarize, I think there are three basic
parameters that need to be defined.

1) Display size. How many rows and how many characters?
Considerations include backlight power and module width. These
modules are much larger than their display area. A 8x2 will fit in a
1U module. You can probably find some 16x2 that will fit into a 2U
module. The microcontroller could be implemented to support either
format with an additional input mode select pin.

2) Electrical interface. You want to use the 14 pin parallel
interface LCDs to best maximize availability. You don't want to use
this many pins as the AtomPro has limited I/O. Using the AtomPro LCD
commands requires that you use 7 pins for the display which is still
too many. SPI and serial are options to reduce the number of pins
used. SPI could be shared with the DAC by using another I/O pin as
the chip select. This obviously would not be retrofitable or code
compatible to the PSIM. Another option is sharing hardware serial
with MIDI (as I implemented with a MIDI sysex command). Again,
multiple modes could be implemented with an additional input mode
select pin (I implemented both 57600 serial and MIDI sysex in my
microcontroller)

3) Prototcol. How do you want to communicate with the LCD? Do you
want general purpose cursor positioning? Do you even want a cursor (I
turned it off on the 8x2 to save a character space). Do you want
scrolling? Do you want the second line to be contiguous with the
first, or, is overwrite mode sufficient. Do you want horizontal
scrolling? (I chose contiguous lines with both scrolling and
overwrite. I also did not implement general cursor position commands
but rather start of line1, start of line2, back 1 position, & forward
1 position)

4) Additional features. With a microcontroller you can use additional
pins for extra features. I added 4 digital outputs to expand my PSIM
capability and also a MIDI status LED. Most anything is possible.

Here are some links of possible interest (sorry, they will be long).

PSIM in 2U MOTM format showing number of pots, connectors, & switches:
modularsynthesis.com/modules/synthmodules/synthmodules.htm

8x2 display in 1U MOTM format:
modularsynthesis.com/modules/synthmodules/PSIM-Display/PSIM-Display.
htm

Partway down this page is a link to my display controller spec:
modularsynthesis.com/modules/synthmodules/PSIM-Display/DJB-
PSIM%20LCD%20display%20spec.pdf

20x2 display in external package (e.g. too large to panel mount):
modularsynthesis.com/display/display.htm

Comments?

Dave