LCD 16x2 Shield Kit only displaying solid squares

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jemenake
 
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LCD 16x2 Shield Kit only displaying solid squares

Post by jemenake »

My LCD 16x2 Shield Kit is only displaying solid rectangle characters on the top row and nothing on the lower row. (This is when I upload the demo sketch which is supposed to display "Push the buttons" and then display (and serial dump) "UP", "LEFT", "RIGHT", "DOWN", and "SELECT" when you press things.

Nothing but solid squares show up, no matter what I press. When I open the serial console, I'll sometimes see a bunch of "UP" or "LEFT" messages. These seem to be sometimes correlated with pressing some of the buttons (eg. sometimes I'll get a string of them without pressing any button... sometimes I'll press a button and not see any messages, yet sometimes the messages seem to start/stop around the time I press/release a button, but it's not just the Left and Up buttons that can cause this).

When I run the I2C scanner sketch mentioned here (viewtopic.php?f=22&t=90133&hilit=lcd+shield#p454537), I see the "0x20: Found!" message.

Including the first three of five photos of the solder connections (as is the customary request when people report problems with the kit, here).
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IMG_1147.jpeg (144.68 KiB) Viewed 264 times
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IMG_1148.jpeg (128.18 KiB) Viewed 264 times
IMG_1149.jpeg
IMG_1149.jpeg (237.54 KiB) Viewed 264 times

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mikeysklar
 
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Re: LCD 16x2 Shield Kit only displaying solid squares

Post by mikeysklar »

Two things to start with here:

1) That soldering looks like the pins might be shorted. You will want to review that with a mutlimeter checking continuity to see if there is a connection between solder points.

2) A potentiometer is included (blue plastic piece) for adjusting contrast. That can often result in dark blue squares being scene if it is full on in dark constrast.

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jemenake
 
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Re: LCD 16x2 Shield Kit only displaying solid squares

Post by jemenake »

Yeah... I know about the potentiometer, and I'm able to adjust that to either show the rectangle chars or just show a blank display (besides, were it to be a screen contrast issue, that wouldn't explain the spurious button events).

I realize that it looks like there's solder meniscus between the pads, but I'm pretty sure that's light reflecting/refracting through the flux. In a few places, I tried to scratch the flux away, but that just makes it turn white (as it fractures) unless you get it all off, at which point, you're risking scratching the mask over the traces (at which point you do get a short).

I'll take an even closer look... maybe post some better photos.

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mikeysklar
 
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Re: LCD 16x2 Shield Kit only displaying solid squares

Post by mikeysklar »

A multimeter resistance / continuity test would be a reliable way to confirm you do not have any soldering issues. It's good to get confirmation there before moving forward with troubleshooting.

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