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Is it a 5 volt display or does it use some other voltage?
Are you sure you have the power connected to the correct pins?
The difficult we do right away...
...the impossible takes slightly longer.
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It's 5vdc from the looks of it. I would think I'm certain having checked multiple times, but the display disagrees with me, since it just sits there dead as a fish when it's supposed to be printing "Hello World"
I need to order a multimeter from amazon. I suppose I'll do that today.
Real programmers use butterflies
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Are you giving the display time to boot before sending the display string?
The difficult we do right away...
...the impossible takes slightly longer.
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the sample program has a delay in it - presumably for that. What's curious to me is the backlight isn't even coming on.
Real programmers use butterflies
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Some displays require you to send a command to turn on the backlight.
The difficult we do right away...
...the impossible takes slightly longer.
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I'm almost certain this one is voltage controlled based on the schematic I'm working with - it's got a potentiometer wired between one of the pins and the power source.
Real programmers use butterflies
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You should check whether the display takes inverted serial input instead of normal.
The difficult we do right away...
...the impossible takes slightly longer.
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That's interesting. I wouldn't know since this kit has zero instructions. It's a clone of the Arduino Mega 2560 and presumably all of the gear in the kit (like the display) is supposed to work out of the box just like the arduino stuff. If not, then I may as well throw it away since there are no instructions.
That said, the pinouts for this LCD and the one in the Arduino provided sample are all labeled the same except 2 pins have a different name on the schematic - "A" vs "LED+" and "K" vs "LED-" but i think they are the same thing, given the other 14 pins are identical, and those are for the backlight according to the schematic
Real programmers use butterflies
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K=kathode/-, A=anode/+; so indeed a generalisation of LED-/LED+.
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Assuming the connections are proper, the backlite should work if power is present. Are the character segments doing anything (I'm guessing it's a 16x2 or similar)? It's been my experience that the segments 'get slightly darker' when power is applied, regardless of backlite. Also, there's the contrast voltage to consider.
"the debugger doesn't tell me anything because this code compiles just fine" - random QA comment
"Facebook is where you tell lies to your friends. Twitter is where you tell the truth to strangers." - chriselst
"I don't drink any more... then again, I don't drink any less." - Mike Mullikins uncle
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jeron1 wrote: It's been my experience that the segments 'get slightly darker' when power is applied, regardless of backlite
Thank you! That's helpful.
It's not doing anything - it's as dead as fish, meaning I've either wired it catastrophically wrong or it came dead on arrival. I've checked the wiring many times, so at this point I'm kind of at a loss.
It's why I wanted to know if anyone knew how to simply get power to thing just so I can prod it for signs of life.
Real programmers use butterflies
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Does turning the pot from one extreme to the other do anything noticeable?
"the debugger doesn't tell me anything because this code compiles just fine" - random QA comment
"Facebook is where you tell lies to your friends. Twitter is where you tell the truth to strangers." - chriselst
"I don't drink any more... then again, I don't drink any less." - Mike Mullikins uncle
modified 2-Oct-20 13:33pm.
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Nope. I even tried wiring/shorting around the pot but nothing.
Real programmers use butterflies
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The pot is for contrast so you generally can't go around it (unless you're using fixed resistors). The fact that the backlite does nothing, is suspicious like there's no voltage. Without a multimeter it's difficult say, you wouldn't happen to have a discrete LED and a 1K resistor, that you could use as a kind of 'voltage' probe?
"the debugger doesn't tell me anything because this code compiles just fine" - random QA comment
"Facebook is where you tell lies to your friends. Twitter is where you tell the truth to strangers." - chriselst
"I don't drink any more... then again, I don't drink any less." - Mike Mullikins uncle
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Yeah but I'm not sure which pins i need to check. I think i know which are the data pins, but the control pins labels aren't very clear. It's why I was hoping someone could tell me at minimum, which of the 16 pins on this apparently standard LCD interface I need to wire up to show signs of life.
Real programmers use butterflies
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I would check pins 1 and 2, generally pin 1 is ground and pin 2 is 5v, if you don't have this nothing else matters. Similarly, pin 16 is ground for that backlite and pin 15 is the current limited 5v input for the backlite.
"the debugger doesn't tell me anything because this code compiles just fine" - random QA comment
"Facebook is where you tell lies to your friends. Twitter is where you tell the truth to strangers." - chriselst
"I don't drink any more... then again, I don't drink any less." - Mike Mullikins uncle
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Thank you! I'll give that a whirl.
Real programmers use butterflies
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honey the codewitch wrote: I've either wired it catastrophically wrong or it came dead on arrival
If you bought it off of ScamBay then this could be the problem. Selling broken electronics is a huge thing on the auction sites. I avoid the batteries too... I saw a clear pattern from multiple sellers where they would sell me 50% good batteries and the other half bad.
I've got some really good stories to tell about ScamBay... I once bought some flood lights off the site. I bought eight of them and the seller only sent me six. He fought me in the dispute and I suddenly realized that I could use the FedEx package weight to prove that it was impossible that the shipment contained 8 of them.
Best Wishes,
-David Delaune
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Got it new off amazon. Only concern is it is a knockoff made my elegoo and not an arduino branded kit. It was a lot cheaper so if i have to order a replacement LCD screen I'm probably still money ahead.  Although that's not taking into account the aggravation of testing an LCD screen for signs of life.
Real programmers use butterflies
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If it's elegoo then really don't worry, they are one of the better ones, and consistantly much of thier gear is of really high quality.
I have a number of elegoo products, and to date I've never had a problem with any of them. In fact I find the cheep bundled Arduino Uno clones are often better constructed than the original ones and half the price!
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First thing to do: Check your wiring, especially ground and the supply voltage. If that does not help, get yourself the datasheet of the display (the one that you have, not the one you assume you have!). I have had such things before. in my case it was a MAX232 Rs232 level shifter. I wired it up according to the datasheet from Texas Instruments and the output voltage levels were not anywhere near RS232 specifications. Then I got the original datasheet and one of the external capacitors was indeed connected to ground instead of VCC. Now it actually works.
Edit: Have you tried to read something from the display's registers instead of writing? This way you might cut some corners. I would also take a look at the signals with my oscilloscope, but I assume you don't have one just waiting for something to do...
I have lived with several Zen masters - all of them were cats.
His last invention was an evil Lasagna. It didn't kill anyone, and it actually tasted pretty good.
modified 2-Oct-20 14:29pm.
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Grrr, yes it is one of those 16 pin interface LCDs. I think you're probably right that it's a bad jumper wire or something. I guess I need to go ahead and order a multimeter. I just overlooked it when i got the kit.
Real programmers use butterflies
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Get yourself the datasheet and take a good look at the pinout of that connector. Never assume anything. Guessing never helps.
I have lived with several Zen masters - all of them were cats.
His last invention was an evil Lasagna. It didn't kill anyone, and it actually tasted pretty good.
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I know that the pinout is a de facto standard 16 pin interface for small LCDs like this. I don't need to assume anything about it. I just need to get it to respond.
A multimeter will help. A datasheet won't solve my current issue.
Real programmers use butterflies
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