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 Posted: Jul 04, 2012 - 12:09 PM |
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Joined: Feb 16, 2007
Posts: 698
Location: Israel
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I have an ATMEGA328 running from internal RC, 2x16 LCD connected in 4 bit mode using peter fleury's library. The LCD works fine for about 10 seconds and than it will show nothing or blocks on the 1st line only.
If I disconnect the power and reconnect quickly, it won't load again. If I'll wait for a few minutes it will work again for 10 second or so and the same thing will happen...
I checked the voltage on the LCD / AVR / another IC in the circuit. All are dead 5V so they are not shorting to power rails.
Also, when plugging in the JTAG connector when the board is working will cause the LCD to display blocks in the upper line and nothing in the bottom line. |
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Posted: Jul 04, 2012 - 02:14 PM |
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Joined: May 01, 2003
Posts: 577
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| Not a lot to go on... but is there a capacitor somewhere it shouldn't be on the LCD circuit? Or perhaps an error in the contrast voltage circuit ? |
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Posted: Jul 04, 2012 - 02:17 PM |
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Joined: Oct 30, 2002
Posts: 5720
Location: The Netherlands
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| Seems the connection is fragile. Glitches on E maybe? |
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Posted: Jul 04, 2012 - 02:28 PM |
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Joined: Feb 16, 2007
Posts: 698
Location: Israel
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| I'll pull out the scope and observe the enable line... might be a good idea! |
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Posted: Jul 04, 2012 - 03:11 PM |
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Joined: Mar 27, 2002
Posts: 18545
Location: Lund, Sweden
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| I'd start with measuring what the current consumption of the whole shebang is, sit down with a cuppa' and think over if the current consupmtion is reasonable. |
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Posted: Jul 04, 2012 - 07:37 PM |
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Joined: Dec 11, 2007
Posts: 6848
Location: Cleveland, OH
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And test it without the backlight on.
JC |
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Posted: Jul 04, 2012 - 10:06 PM |
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Joined: Jan 03, 2004
Posts: 1637
Location: Apalachin, NY, USA
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slow_rider wrote:
The LCD works fine for about 10 seconds and than it will show nothing or blocks on the 1st line only.
This sounds like the reset state of LCD. Something is probably causing it to be reset.
In addition to the suggestions already posted here, I'd put a scope on the +5V line at the LCD.
Don |
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Posted: Jul 05, 2012 - 12:01 AM |
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Joined: Feb 16, 2007
Posts: 698
Location: Israel
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| So I pulled out the scope and everything looked fine but the power supply. I am using a switching module from Murata that clearly stated no need for a capacitor after it. I could see some ripple and if I could see it that's not good. I've installed a 100uF cap and 1uF at the MCU and other ICs and LCD supplies. Believe it or not it did the trick. |
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