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I seem to be having a weird and frustrating issue.

I have a Nokia 1616 LCD to which I am displaying images stored on an SD card. Everything worked fine when I was breadboarding it but when I assembled the circuit on a etched PCB, that's when the trouble started.

When I power on the circuit I see the lcd backlight with normal expected brightness. However right after that (when the avr starts initializing the LCD I presume), the brightness decreases dramatically and the image shown on the lcd is all streaked with color lines and has sort of whitewashed effect. Like the image is bleeding (don't have any pics as I removed the LCD to try n solve the issue).

However at this point if I press the reset button on my circuit (reset avr) and hold it for a brief moment I see the LCD act normal with the image shown as it should be.

Googling didn't help much. A single post on avrfreak suggested that this streaking happens due to 5v signal being applied to 3.3v terminals of the LCD. I am using a bss138 to do level conversion. So to check those I wrote a test program outputting 5v on all the output terminals and as expected I got 3.3v on the lcd inputs. So that's not the issue.

Another thing I noted is that on my breadboard the circuit pulls in about 200ma but on the PCB its constantly pulling in around 350ma.

This along with the backlight dimming is making me believe that there must be a short somewhere .

Am I along the right path. Has anyone had any experience of such kind?

This is what it looks like enter image description here

This is what is should look like enter image description here

Thanks!

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  • \$\begingroup\$ It is also possible the LCD drains more because of the fault condition. If you power it on shortly with as many measurement devices you have along the power rails, both 5V and 3.3V, what do you see? All stable? Are you using the exact same components for all parts of the power generation now as you did before? \$\endgroup\$
    – Asmyldof
    Commented Jul 6, 2015 at 8:01
  • \$\begingroup\$ Yes I am using exactly the same components. I tried this with another LCD and the same issue happens \$\endgroup\$
    – Ankit
    Commented Jul 6, 2015 at 8:23
  • \$\begingroup\$ Is your power supply stable enough? Is the AVR driving other power hungry components which are inactive during reset? Check if the LCD's supply is at the designed voltage (3V3?) when the error shows. \$\endgroup\$
    – JimmyB
    Commented Jul 6, 2015 at 10:26
  • \$\begingroup\$ Can you please share the circuit diagram for interfacing the 12 pin Nokia LCD with AVR as you have done in this project. I am really in need of this circuit. \$\endgroup\$
    – user83006
    Commented Aug 11, 2015 at 11:34
  • \$\begingroup\$ sure. you can find it at i.imgur.com/4kko24I.png \$\endgroup\$
    – Ankit
    Commented Aug 11, 2015 at 11:53

1 Answer 1

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Have you thoroughly inspected your PCB for shorts?

You can use a continuity tester function (or the lowest ohm range) of a multimeter to test whether you have shorts between traces that shouldn't be shorted (do this with power disconnected!).

Better if you do this test with the LCD (and any other socketed component) disconnected, so as to minimize apparent shorts due to their presence.

This, together with visual inspection using a good loupe, should give enough confidence about the presence of shorts due to the PCB fabrication or the soldering step.

Keep in mind that, since you already have some component soldered, if you find a short it could be due to a component placed between the traces where you detect the short, so you should desolder every component and test them individually, unless you spot a dead short between the traces due to fabrication residues or soldering.

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  • \$\begingroup\$ just finished doing that. there was a short. However fixing it only brought the current pulled in by the circuit within the expected range. The streaks are still there \$\endgroup\$
    – Ankit
    Commented Jul 6, 2015 at 13:56
  • \$\begingroup\$ Problem fixed. There was a short in the lines where I soldered the LCD FRC to the PCB. I did check it last time and it was fine. Don't know how I missed it the first time round. Lesson learnt. Not to solder FRC directly. Problem is for these LCD the connector is hard to find. Thanks ! \$\endgroup\$
    – Ankit
    Commented Jul 7, 2015 at 7:00

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