Most, if not all, of the inexpensive LCD displays aren't meant for use in bright sunlight, but it occurs to me that perhaps if I reversed the pixel coloring, i.e., blue pixels (actually turned off) on white background (turned on), I might get a fairly good result. I don't know if any library supports this, but it sounds doable. Has anybody tried this?
Thanks in advance for any help.
All an LCD library does is make it possible to send instructions to the HD44780 without knowing much about the details of it's instruction set. Since the HD44780 itself cannot do what you want to do you won't find a library that will do it either.
Don
After studying the situation for awhile, it clearly can be done, and I'm surprised I haven't found it on the internet somewhere.
If I use the KB of EEPROM on some little workhorse chip like the ProMini 328, I can store all capital and lower case letters, numbers, and virtually all punctuation symbols in inverted format, 5 bytes per symbol, using the same bit pattern system used to create special characters for the HD44780 LCD, but bit-inverting them.
Then I write some code so that I can forward an alphanumeric string to this ProMini from my main processor using SW or HW serial. The ProMini picks the string apart, character-by-character, uses the integer value of each character to index a switch case statement, each case of which creates a special character from the appropriate data in the EEPROM, then sends that to the LCD display. I suspect that the whole process will not cause a noticeable delay in the output, but of course, that is an area of risk to be examined.
It is a fair amount of code and processing, but at $2.50 a pop, I can afford to devote a ProMini to act as a special driver chip for the LCD. I have plenty of need for inexpensive outside displays, so I'll pursue it along the lines I've outlined.
If I use the KB of EEPROM on some little workhorse chip like the ProMini 328, I can store all capital and lower case letters, numbers, and virtually all punctuation symbols in inverted format, 5 bytes per symbol, using the same bit pattern system used to create special characters for the HD44780 LCD, but bit-inverting them.
Creating the bit patterns is quite straightforward, getting more than eight of them to display via an HD44780 controller is not.
Don
jrdoner:
After studying the situation for awhile, it clearly can be done, and I'm surprised I haven't found it on the internet somewhere.
And there is a really excellent reason for that!
I don't need eight; I only need one. I can produce one at a time, store it to CGRAM, then instruct the display to print it.
I just keep parsing an incoming string, call up the stored data for the inverted format of the latest character, one at a time, create that character in CGRAM, and then call the write statement to display it. Once I've written it to display, I can reuse the same CGRAM location, as many times as I want. I don't know what the maximum print rate might be, but it will probably exceed any practical rate at which the a human might need to read it.
Sorry, Don and Paul, that you can't sort out this concept. When I learned engineering about 35 years ago, we were taught that good engineering often involved getting more out of product than might have been the original intention. Perhaps I was misinformed.
When I learned engineering about 35 years ago ...
So you're just a babe in the woods, relatively speaking.
I just keep parsing an incoming string, call up the stored data for the inverted format of the latest character, one at a time, create that character in CGRAM, and then call the write statement to display it.
Have you considered the fact that each time the LCD controller refreshes the multiplexed display it goes back to the CGRAM location to retrieve the required bit pattern. What you are going to see is the latest character you have sent to the CGRAM in every DDRAM position that you have used.
Back to the drawing board.
Don
jrdoner:
Perhaps I was misinformed.
Well, I don't know whether you were misinformed then, but you certainly have thoroughly confused yourself now! 
Do you really not know how a character generator works? I was programming them while you studied engineering!
Addendum: What you need to do is to carefully study this exercise to see what you can and what you cannot do, and how it actually appears on the LCD. It is rather a favourite of mine now.