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Topic: (Solved)New I2C LCDs wont work (Read 1 time) previous topic - next topic

Tumbleweed

Jun 23, 2012, 12:15 am Last Edit: Jun 23, 2012, 03:56 am by Tumbleweed Reason: 1
Hello Aeduino Forum,
That is what my new LCDs are supposed to read with the example from fm's new Liquid crystal library.
Just get lightly blinking backlight and the custom characters jumping around on line one.
Only four wires, checked them 20 times, tried different Ardy's, found a I2C lcd library made especially for the chips on the I2C breakout, got nuttin'. The address is right, tried a bunch of others and didn't get a glimmer. Tried both 4.7k and 10k resistors to grnd from the slc and sda pins, i at least got a steady backlight but nothing else with either value. Also tried 3 of the LCDs all act the same.

I am using the old wire.h library, I have read it is flaky.
Any other suggestions?
TomJ
Einstein once said you don't really understand anything until you can explain it to your Grandmother

fm

Hi TomJ,

which LCD I2C backpack are you using?
   

Tumbleweed

#2
Jun 23, 2012, 01:07 am Last Edit: Jun 23, 2012, 01:14 am by Tumbleweed Reason: 1
FM,
Some Chinese knockoff, from GE Tech, the I2C chip on the back is a PCF85747. Next line is K63331, but that is usually a date code.
I found am I2C library that said it was for that chip on the Playground, but even with the right address and their code I got nothing. No
blinking backlight no lightly scrolling characters.
The contrast needed adjusting to see the characters at all on your code, but that is usual.
By the way how do I positively turn on the backlight with your library and a I2C controlled backlight?
Thanks,
TomJ
Einstein once said you don't really understand anything until you can explain it to your Grandmother

fm

Hi TomJ,

that chip is very much like the one I use on my backpack: the NXP PCF8574A
The library is well qualified with that chip and should work out of the box if you/they haven't changed the I2C address mapping.

The contrast is adjusted with a trim pot. Do you have a picture of the backpack or a schematic?
   

Tumbleweed

I think I can get a picture, but it isn't much good.



Thanks again
TomJ
Einstein once said you don't really understand anything until you can explain it to your Grandmother

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