LCD App Mod and the propeller

bambino

http://www.parallax.com/Store/Accessories/Displays/tabid/159/CategoryID/34/List/0/Level/a/ProductID/53/Default.aspx?SortField=ProductName%2cProductName
Looking at the data sheet for the LCD App Mod reveals that it can be run at three volts. I f I spin a board that would hook the propeller up to the 2X10 header would I have a problem with the push buttons. They were designed for 5 v usage very cleverly to not interfer with bus signals, would dropping the voltage to 3.3 make the tacktile switches incompatable with the LCD bus?

Chris Savage

Bambino,

I’m curious how you deduced that the module would run @ 3.3V? The Hitachi chipset specification is for 5V. I can’t see the LCD functioning with less than 5V, though since it is a compatible chipset (not exact) I guess it would have to be tested.

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Chris Savage
Parallax Engineering

bambino

Features
· 5 ´ 8 and 5 ´ 10 dot matrix possible
· Low power operation support:
¾ 2.7 to 5.5V
· Wide range of liquid crystal display driver power
¾ 3.0 to 11V
· Liquid crystal drive waveform
¾ A (One line frequency AC waveform)
· Correspond to high speed MPU bus interface
¾ 2 MHz (when VCC = 5V)
· 4-bit or 8-bit MPU interface enabled
· 80 ´ 8-bit display RAM (80 characters max.)
· 9,920-bit character generator ROM for a total of 240 character fonts
¾ 208 character fonts (5 ´ 8 dot)

¾ 32 character fonts (5 ´ 10 dot)

Hay Chris,

This was the part out of the data sheet that got me thinking!

Sapieha

Hi bambino


Only if that display have "HD44780U" controler but not "HD44780S"

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Nothing is impossible, there are only different degrees of difficulty.
For every stupid question there is at least one intelligent answer.
Don't guess - ask instead.
If you don't ask you won't know.
If your gonna construct something, make it·as simple as·possible yet as versatile as posible.


Sapieha

bambino

Thanks Saphiea,

Can I be sure what I will get when I order one!

Chris Savage

Okay, so I went back to the datasheet and looked up the information and you’re right…it does list the chipset as having those features. I think where I am a little confused is that I have almost never gone back to the Hitachi datasheet since every LCD I have ever purchased always had a copy of the relevant information. But, on every LCD display I have (parallel) the datasheet for the display lists the unit was requiring 5VDC +/- some % (it varies a little). All of these displays have Hitachi HD44780 chipsets on them, though I never did check to see if they were U or S. In any event, I can’t say the Parallax display will work at 3.3V mainly because it is not an HD44780 chipset, but a compatible one. Even if we had displays with that chipset, it had been designed with 5V use in mind. You can try it though.

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Chris Savage
Parallax Engineering

bambino

Thanks for the info Chris!
It's for a friend though, so I don't feel to brave about it.

Chris Savage

The next time I need to use a parallel display I am going to see if it runs at 3.3V. Since most of my displays are parallel anyway there is no serial interface chip to worry about for power considerations, just the Hitachi chipset.

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Chris Savage
Parallax Engineering

bambino

I will be hanging on the edge of my seat. Thanks.
It would be nice to be able to throw in a cheap lcd on my next parallax order.
I have a serial backlit one that I use for debugging, but a little pricey for some projects!