LCD inverted control/data lines...

[dietmar]

Hi, i am using a standard 2x16 lcd to work with my pic. It is connected as the following: Control and data lines are connected to a flat cable, which is connected to a Schmitt Trigger inverter to prevent noises on the cable. And this is the problem: The Schmitt trigger inverts... What do i have to change in lcd.c to make my display work with this inverted logic? Has anyone tried this before and has anyone a driver to post here??? Thanks....

[Ttelmah]

You would need a completely different driver approach. Remember the data lines, are _bi-directional_, and the busy status line back from the LCD is used to time the LCD accesses. With a simple buffer in the data lines, you are going to have to slow all operations down to the point where you don't need to use handshaking at all. Since some operations are slow (like the clear screen command), this will involve very long delays indeed. You would be much better off connecting the data lines via a bi-directional non-inverting buffer, and using the R/W line to control the direction. Thn only the logic on the control lines would need to be inverted.
It can be done using mono-directional control, probably the 'best' way would be to have a timer interrupt at perhaps 1/100th sec intervals, and use a buffer, sending just one character to the LCD on each interrupt. This is slow enough to meet the worst case timings for all simple commands except clear.
I'd suggest re-thinking the hardware a little. Otherwise some significant code is going to be needed.

Best Wishes