LCD Display Options
2006-03-10 by djbrow54
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