HD44780 Double Charachters when using long LPT Cable

[spauka]

Hi All,
Just incase anyne has this problem in the future, when using a long LPT cable extender with my lcd screen, i had an issue of charachters sometimes doubling up, and scroll becoming rather jerky as a result.

After a while of scratching my head, I solved the problem by attaching a 0.01ɥF capacitor between Vss (Gnd) and the Enable Pin, so between Pin 6 and Pin 1 on the LCD smartie circuit.

Apparently there was a bit of noise appearing due to the long distance which caused the LCD to read multiple enable signals on single charachters. The capacitor smoothes out the noise that appears.

Hope this helps someone.

[caesar]

Great find!
Way better than increasing the timing.

[spauka]

Actually, it was rather strange. Increasing the timing only made the problem worse. Instead of a few sparse double letters, all of them doubled up.
This fixed that problem.