I have covered this in a previous thread (archived).
Basically, using a 40X portC pin to drive this particular LCD that I'm using doesn't work.
The cause is the minimum pulse out is approx. 300uS using high/low code.
Initially I was able to work around this by using a standard Output pin instead.
However, the project has evolved to needing that pin for another function, leaving only portC pins available.
So, I was forced to find an answer to the original problem.
It turned out that using a "pulse shortener", consisting of a "differentiator" circuit, did the trick, and it now works fine.
I used a 0.01uF capacitor in series followed with a 1000 ohm resistor to 0V, plus a small diode across the resistor, to kill the unwanted negative-going pulse.
This information is posted for the benefit of anyone else that may have an LCD that doesn't respond to the portC high/low commands for the Enable line.
kenmac
Basically, using a 40X portC pin to drive this particular LCD that I'm using doesn't work.
The cause is the minimum pulse out is approx. 300uS using high/low code.
Initially I was able to work around this by using a standard Output pin instead.
However, the project has evolved to needing that pin for another function, leaving only portC pins available.
So, I was forced to find an answer to the original problem.
It turned out that using a "pulse shortener", consisting of a "differentiator" circuit, did the trick, and it now works fine.
I used a 0.01uF capacitor in series followed with a 1000 ohm resistor to 0V, plus a small diode across the resistor, to kill the unwanted negative-going pulse.
This information is posted for the benefit of anyone else that may have an LCD that doesn't respond to the portC high/low commands for the Enable line.
kenmac