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Author Topic: 128x64 st7920 LCD  (Read 1350 times)
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North Queensland, Australia
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Hi, I have a st7920 graphics lcd, the same one that works with the LCD12864 library  at http://www.arduino.cc/playground/Code/LCD12864

I have written a class to run the screen using my shift class over 2 74hc595 registers. I don't use all 16 pins so I want to add a bit of functionality.

1 pin controls a transistor which turns the back light on or off. Thhat works fine but,

I want to use another pin to fully reset the screen. I am just not sure weather xreset is an input or output. And if it is an input the shift register should be able to control it.


I have attached xreset.png which is an excerpt from the data sheet for it.

All it says in the data sheet pin description is 'active - low'

Does this indicate that I can have xreset high for normal use then take xreset low for the reset pulse width to reset the device.

Just want to check before I put 5v into an output.


* xreset.png (17.6 KB, 939x467 - viewed 22 times.)
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Hofstadter's Law: It always takes longer than you expect, even when you take into account Hofstadter's Law.
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I guess you've probably answered your own question by now as it is more than a month old; but the answer is yes.

btw the st7920 controller has a serial mode, so you can drive it from an Arduino using just 2 pins. Unfortunately the standard libraries don't support the serial interface because they require the device to be readable as well as writable to avoid the need for a frame buffer, but I have a basic library for it.
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I have almost finished my library and it supports 8-bit parallel write mode via parallel or shift registers

once finished, it will be usable in full 8-bit Read/Write mode via
*parallel ( 12 upto 15 pins )
*shift registers ( both in and out, 4 to 5 pins used hopefully... testing will prevail )
*shift registers via spi


But no I had not answered my question. It was not on my priority list so I let it slide.
So thank you, I will try it soon. I would like to see your library and exchange ideas if you have it posted anywhere.
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