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Sweden
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Hey!
I'm using a 16x2 LCD display (https://www.sparkfun.com/products/10862) with a serial enabled backpack (https://www.sparkfun.com/products/258).
However, it doesn't work, and regardless how much I try, the display stays totally blank.
Shouldn't I be able to see black squares if it got power?
I've tried to change the contrast, but It's still blank..
Current is flowing trough the backpack GND/5V pins as well, so I'm afraid that there's something wrong with the display.

Help is appreciated !
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Western New York, USA
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Is your backlight working?  I know that some displays, specifically the ones with white characters on a blue background, are virtually impossible to use without the backlight.  I don't know about this one, but that could be your problem.

How did you deal with the fact that the LCD has 18 pins but the serial backpack is designed for a 16 pin display?


Don
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Sweden
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No, the backlight doesn't work, which I think is strange since It should lit if the display has power.
Maybe the LED is turned off if not enabling it trough programming.
The display got 18 pins because of the 2 extra LED colours, since it's RGB.
The backpack is only connected to the red LED, which means that you have to connect the other LED's separately if you need them.

My display is still dead tough.. :/
« Last Edit: January 20, 2013, 02:37:16 pm by Jellycow » Logged

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The last thing you did is where you should start looking.
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You should have +5 Volts to the Red, Blue or Green (16,17,18) anode for the back light.
 Pin 15 or the cathode (K) should go to a resistor (Try 220 ohm).
The other end of the resistor goes to 0 Volts.
If Red is not working try one of the other 2 colours.
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The way you have it in your schematic isn't the same as how you have it wired up!

Sweden
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The thing is that nothing on the display seems to work.. and neither do the LED's.
Characters on the display should be visible without backlight as well.
It's like it's not receiving any power from the backpack even tough I measured the current from the backpack pins to 5v.
« Last Edit: January 20, 2013, 05:25:08 pm by Jellycow » Logged

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The last thing you did is where you should start looking.
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Would you show us a picture of your wiring?
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The way you have it in your schematic isn't the same as how you have it wired up!

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some displays, specifically the ones with white characters on a blue background, are virtually impossible to use without the backlight.

I strongly dispute that.

In an earlier discussion, liudr indicated that s/he has a sparkfun white/blue lcd that remains readable in direct sunlight, without the backlight. and s/he has a picture to prove it.

While liudr hasn't provided the picture yet, I take his words over yours.
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some displays, specifically the ones with white characters on a blue background, are virtually impossible to use without the backlight.

I strongly dispute that.

In an earlier discussion, liudr indicated that s/he has a sparkfun white/blue lcd that remains readable in direct sunlight, without the backlight. and s/he has a picture to prove it.

While liudr hasn't provided the picture yet, I take his words over yours.

Perhaps you should go back and read that post again --> http://arduino.cc/forum/index.php/topic,125666.msg944902.html#msg944902 <--

Don't forget to scroll down a bit to this part --> http://arduino.cc/forum/index.php/topic,125666.msg952237.html#msg952237 <--


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liudr indicated that s/he
Dr. Liu is a 'he'.

Don
« Last Edit: January 20, 2013, 08:21:17 pm by floresta » Logged

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In that post, liudr said, re white/blue display:

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But if I turned off the back light, I can see outdoors.

liudr wins and you lose.
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I guess you forgot to scroll down to the part where he said "I got my first and only white on blue from adafruit. It was slow and needs back light in well-lit indoor environmenit "

Here's a quick and dirty comparison using a project I found in my drawer.  The ancient 16x2 display has no backlight.  The other three photos show the 20x4 display with no power to the backlight under my normal (bright) desk lighting and with simulated sunlight (the only kind we have here in much of the time) from a Maglite.  The last picture is with the backlight powered.

The un-backlit 20x4 display seems to show up better in the pictures than it normally appears.


Don


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I guess you forgot to scroll down to the part where he said "I got my first and only white on blue from adafruit. It was slow and needs back light in well-lit indoor environmenit "

I guess you didn't realize that this is a conversation about white/blue lcd in OUTDOOR environmenit, not INDOOR environmenit.

On that front, liudr said:

Quote
But if I turned off the back light, I can see outdoors.

What he said about INDOOR environmenit is probably irrelevant to this discussion.

Sounds like liudr wins and you lose.

Quote
Here's a quick and dirty comparison

I guess there is this possibility that liudr has superman vision.

But without a picture of his white/blue lcd outdoor, we can never tell.
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I guess you didn't realize that this is a conversation about white/blue lcd in OUTDOOR environmenit, not INDOOR environmenit.
No it is not.  The original poster did not mention anything about his environment.

This forum really is not about who wins and who looses, it is about helping people get their projects working.  

The original poster was concerned that the display on his LCD appeared to be totally blank.  I looked at the description of his display and saw that not only did it have three backlight LEDs (with two extra terminals for the two extra LEDs) but that it also appeared to be one of those displays that is difficult to read when the backlight is off.

I had a similar experience when I first encountered one of these types of LCDs.  When I first used my backlit 20x4 I too thought it was dead but I had the advantage of knowing that my circuit and code were correct since I had merely replaced one display with the other just as I did in the series of photographs last night.  

The original poster asked for help with a display that appeared to be dead and I suspected that the backlight, or more specifically the lack of a backlight, might also be his problem.  You might dispute the fact that these displays are virtually impossible to use without the backlight functioning but that has not been my experience with my display.

The original poster has indicated that his backlight is not functioning and I think it would be best to pursue fixing that problem since I don't think that he wants to be restricted to operating his display only in direct sunlight.


Don
« Last Edit: January 21, 2013, 10:32:46 am by floresta » Logged

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Let me just bring back some memory for you.

You said:

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some displays, specifically the ones with white characters on a blue background, are virtually impossible to use without the backlight.

and I followed up to say that liudr's experience would dispute that, as he said:

Quote
But if I turned off the back light, I can see outdoors.

I never suggested if such a display would be readable (or not) indoors with or without backlight. I only focused on outdoor use without a backlight, as liudr did.

Sounds like liudr prevails once again.
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Sounds like liudr wins and you lose.

This isn't some sort of bizarre game, with winners and losers.

We are trying to help resolve problems here. We "win" if we help the person who asked the question, who also wins if the suggestions work. If not, we need to explore other options.

The original post is a bit vague:

Quote
However, it doesn't work, and regardless how much I try, the display stays totally blank.
Shouldn't I be able to see black squares if it got power?

It isn't clear if the backlight is on or not, from that. Also, wiring errors (eg. to the contrast pin) could account for what you are seeing.
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The backlight does NOT work, and neither does the rest of the display.
When it comes to the wiring error, it seems unlikley since the backpack pins are connected to the right spots into the display from 1 to 16.
It seems more likely that the display itself (for some reason), doesn't recieve power even tough i measured the voltage on the GND/5V pins from the backpack to 5v.
If if the display had power, the backlight would work, it would show black squares instead of characters, and the green and blue backlight on pin 17 and 18 would work, since they're grounded trough the backpack.
I might try to desolder the backpack from the display and see if it works with normal wires. It did work with normal wires (without the backpack) for a couple of weeks ago, but I didn't test it after that, or before soldering on the backpack.
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