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Project Help and Ideas » Black LCD screen

February 03, 2010
by NS
NS's Avatar

I have wired LCD screen from the NerdKit, I think correctly. When I connected battery all I could see on LCD were black squares. Do you guys have any idea what I could have done incorrectly?

Thank you

February 03, 2010
by mongo
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Check your contrast resistor. Might be the wrong one.

February 04, 2010
by NS
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already did. It measures 0.986 kilo-ohm

February 04, 2010
by NS
NS's Avatar

OK. Here are more details. I found out that I did not connect voltage regulator correctly. I am suspecting that I had around 9V going through MCU. That was probably the reason why I saw totally black LCD. Currently only 1st and 3rd row are lit. I have checked all connections from MCU to the LCD with voltmeter and all connections seem to be OK.

Question: By having 9V applied to the MCU did I fry it? Or maybe I just deleted program?

February 04, 2010
by mongo
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OK, you do get the first and third lines as black bars if you are in the programming mode. It sounds as if the display board may still be OK but you might want to check the MCU. If it's not in program mode... something else may be wrong.

February 09, 2010
by NS
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Now I am even more puzzled. I was not able to connect MCU to my computer at all. I tried both NerdKit USB to serial cable and ISP AVRmkii without success. Only when I took MCU out and stuck it into STK500 I was able to communicate with MCU and read its signature. I think MCU is OK. However, while in STK500 I have uploaded "initialload" program that was provided. Now I am not sure whether I deleted boot-loader that was on the chip (occurred to me after the fact).

I am using Laptop with Vista. Don't know if that is important or not.

Questions: 1. Do I have to upload boot loader again 2. Does the fact that I am using laptop and running Vista contribute to my problem 3. Is there any way to tell for sure that MCU is OK

Thank you very much.

December 25, 2011
by wadaltmon
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I had the same problem; I only saw the first and third lines of the display as black squares. All you must do is take the device out of programming mode, then disconnect and reconnect the power. This worked for me.

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