Thread: LCD not working (in known working circuit)??

I just bought a 20x4 LCD on ebay (1x LCD 20x4 HD44780 Blue Backlight headers *USA *fcbusa) advertised to use an HD44780. I just recently got around to testing to see it work, and it doesn't! I placed it in a circuit that i know works, and even tested it with another 20x4 HD44780 LCD, and the circuit works great. But the new lcd i bought just displays gibberish!

I'm really not sure what the problem could be? Does anyone have an explanation for why 2 HD44780's wouldn't work in the same circuit? Maybe i'm over looking something...

here is their ebay page i actually bought it from.

1x LCD 20x4 HD44780 Blue Backlight headers *USA *fcbusa - eBay (item 150326760448 end time Jul-13-09 13:27:23 PDT)

Quite good feeback.

Some of the more modern chips are much faster than the original Hitachi chip and so they will work with shorter delays in the initialisation and write routines. If your new display requires the original timing parameters then it may work if you increase the delays in your code.

Mike.

Originally Posted by Pommie

Some of the more modern chips are much faster than the original Hitachi chip and so they will work with shorter delays in the initialisation and write routines. If your new display requires the original timing parameters then it may work if you increase the delays in your code.

Mike.

Thanks. I'll increase the delays and see if that works.

Well i solved the problem purely by accident...

I needed to use the interrupt pins (atmega16), so i moved the LCD from PORTD to PORTC, and the LCD magically worked! Turns out on my development board i had the RX and TX jumpers connected to the MAX232 and that was somehow interfering with the new lcd, but not the old lcd. Very simple mistake

It's working like a champ now

Thanks all for the help! it was greatly appreciated.