Quick LCD Question

IRobot2

I have two Matrix Orbital (LK204-25) serial LCD's. Same part number but one came from DigiKey and one from Parallax (Item Code 30058).

The Parallax one works great - No problems and is easy to use- . The one from DigiKey just puts garbage up on the screen when I try to send it any thing, even a "clear screen" statement.

Looking at Parallax's web site they say that they have "pre-modified the LCD for Basic-Stamp Compatability". My guess is that whatever they have done is my golden ticket to fixing the DigiKey one. Anyone know what they did?

Thanks everyone,

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Alex Burke
"It is not how smart you are rather, it is how you are smart." -Jon Campbell

IRobot2

Well I found out my problem. With the Parallax LCD I had "mode" in FullDuplexSerial set to "0" (invert rx) and for whatever reason with the non-parallax one I had to chose "2" (open-drain/source tx) to get it to work.

Works great now. But can anyone explain why I had to do this?

'' mode bit 0 = invert rx
'' mode bit 1 = invert tx
'' mode bit 2 = open-drain/source tx
'' mode bit 3 = ignore tx echo on rx

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Alex Burke
"It is not how smart you are rather, it is how you are smart." -Jon Campbell

Chris Savage

Actually the one from Digi-Key should be set to inverted RS-232 by default, whereas the Parallax unit should be set to non-inverted TTL level serial.

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Chris Savage

Parallax Engineering
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