Half of My LCD Lights Up

[Axaday]

Originally Posted by ptsmith24

How did you connect the wire from the button to the board? I have mine pushed into the appropriate pin header (nothing real permanent). In other words, can you disconnect the button from the board (but still keep the wires connected to the button itself)?

My buttons are on a separate breadboard and it is the kind that has two holes for every contact. So I soldered the buttons and the wires separately.

I'll go to RadioShack tomorrow morning and see if I can find new buttons just like the old ones (except with more resistance).

[wyatt]

If it helps anything...
I am running an iDuino with a blue backlight display, too. In the code, you can change the contrast settings, and upload it again. I am using a contrast of 315. You can change those numbers (and any others you would want to change) in the code towards the top. Where it says:

char *  parmLabels[]={"Contrast","VSS Pulses/Mile", "MicroSec/Gallon","Pulses/2 revs","Timout(microSec)","Tank Gal * 1000","Injector DelayuS","Weight (lbs)","scratchpad(odo?)"};
//unsigned long  parms[]={15ul,16408ul,684968626ul,3ul,420000000ul,13300ul,500ul};//default values
unsigned long  parms[]={95ul,8208ul,500000000ul,3ul,420000000ul,10300ul,500ul,2400ul,0ul};//default values

You can change the 95 to 315 (or other numbers) and see how things work. I just changed the "hundreds" number, and there were lots of settings that worked, and lots that looked pretty bad, so you may have to try a few to find a good one. You can check out how I did my build (and see any potential differences between our builds). I am still working on it, but it's coming along nicely.

[Axaday]

After fixing the buttons, I can now adjust the contrast. Turning it to 7 makes it where I can read "Contrast 00000007". But then what? The other half of the LCD still shows white blocks. Should it? How do I go on to another screen?

Edit - Okay I went an found instructions. I can't see a "XX" or "OK". But by positioning the cursor on my first digit and then going one more left, I was able to use it anyway. So I got through the setup screen. Now I guess the thing is working. The screen is a little glitchy and isn't always readable, but it is showing I 000.00 and C 000.38

Edit - When I took it back to the car to take pictures, it was back uncontrasted and I couldn't set it again. So now I've gone into the program and made all of my settings the defaults in the hopes that it will now start up right. I'll go take some pictures now if I can, but basically the right half of the screen stays white blocks except for the occasional wiggling glitch.

[dcb]

Well, progress. Can you post a picture of the lcd "problem"?

[wyatt]

Line 1 should read something like "CONTRAST"
Line 2 should be 16 characters, about 10 numbers, ok, xx (not sure what the xx is for), "0000000315 OK XX"
Mine has never displayed white blocks, the whole display should be controlled together. Things to try (again if necessary)
1. Refresh the code (I had to do this twice for what ever reason)
2. Make sure your wires connecting the LCD to the rest are soldered well on both ends, and that the wire used is solder friendly (not all metals can be soldered).
I guess I don't know what else it could be, it almost certainly has to be something like that, since there shouldn't be any white blocks on that screen.
Cycling through screens is done by using the left/right buttons to move the cursor to OK and pushing the center button. Then you cycle through screens in the order of the code posted above... Contrast, VSS Pulses/Mile, MicroSec/Gallon, etc. until you finish your setup and then you should be taken to one of the screens that shows Instantanious MPG/Speed/Current MPG/Distance (or similar).
Do you have a picture of your setup that you could post? That way it could be verified that everything looks as it should.

[Axaday]

Is it right at the start of the program where I can change the defaults? That's what I've been doing, but I just took it back to the car and managed to adjust the contrast and it is still defaulting 0 Contrast and 100 VSS when I've changed them to 2000 and 4000.

Edit - Actually, since I'm only getting the first 8 digits of the field, I'm not sure what the defaults are showing.

Edit - I rechecked the LCD connection with my multimeter earlier before taking it to the car for the first time today. It shows no resistance on each solder, but positions 2 and 3 on the LCD showed connectivity. It isn't the solder and the wires are nowhere near each other on the other ends.

[dcb]

Couple clarifications:

Once the values make it into the eprom (when you make it through all the setup screens) the program defaults are ignored.

Also the valid values for contrast are 0 to 255. The wrap around at 255 so Wyatts mention of 315 above is really a 60. Not a lot of room for a fancy editor so that's what is going on there.

Ax, I suspect one of your lcd lines isn't set up right. Which model did you have again?

[Axaday]

Originally Posted by dcb

Couple clarifications:

Once the values make it into the eprom (when you make it through all the setup screens) the program defaults are ignored.

So what do I need to do? When I take it to the car now, it is trying to disply "IM000.00" and "CM000.00". I say trying because the sides of the M's come on and off. And also because the contrast is always where I can't see, so I have to push all 3 buttons to go through setup. But I have to do that every time because it nevers saves my changes once it is unplugged.

In the long run, I'll be leaving it plugged in most of the time, but right now I'm carrying it in and out so that I can do internal investigations. But if I cleared its memory somehow would it forget that it had been through the setup and go by the defaults?

Also the valid values for contrast are 0 to 255. The wrap around at 255 so Wyatts mention of 315 above is really a 60. Not a lot of room for a fancy editor so that's what is going on there.

Okay, I'm changing mine to 60.

Ax, I suspect one of your lcd lines isn't set up right. Which model did you have again?

16x2 LCD Module White Characters Blue Backlight

I'm going to recheck the solders and the diagram now.

[wyatt]

I think I may have mis-spoke, your MPGuino should be storing your Contrast, VSS Pulses/Mile, MicroSec/Gallon, etc. to EEPROM (meaning it doesn't require power to save). This way people don't lose their presets when they update the code, so you probably have numbers stored. I am going to guess that if you were able to get to the second screen when all you saw was blocks, you may be able to scroll to the "tens" number and adjust it (Even if you can't see it), and same with the "ones" number.
BTW, I am able to hook the MPGuino up to the the computer by USB connection and operate it just like it was in the car (only I don't get signals, like with my car off). It may be easier for you to do things from your computer.
NOTE:
Since I have only changed the "Hundreds" number, I have no idea what the other two numbers even do, so if you wanted to, you could go through all of the 100 settings (by changing the numbers you can't see) pretty easily if you were up for it.

[dcb]

Originally Posted by Axaday

Edit - I rechecked the LCD connection with my multimeter earlier before taking it to the car for the first time today. It shows no resistance on each solder, but positions 2 and 3 on the LCD showed connectivity. It isn't the solder and the wires are nowhere near each other on the other ends.

lcd pins 2 and 3 are about 10k ohms apart on a guino sitting on my desk.

[Axaday]

This is actually new. I've been trying to just tweak inside (and I retouched every solder and am sure they are good) and when I plug it into my laptop, I get a regular screen that twitches. What I mean by that is that it usually shows nothing but every second or so a vertical line appears on one of the places and disappears. But when I push all 3 buttons to get the setup screen, it displays this in living color:

[dcb]

I think you were on to something with the ohm readings. I didn't see any serious connectivity between any lcd pins except the common ground ones.

Edit, and the fact that the behavior is changing is a sign that something is flaky.

[dcb]

Also, it is just the left and right button now to get to the setup screen (got tired of accidentally resetting the tank or current trip).

[Axaday]

Some of the green area around the solder points on the LCD is extra glisteny. Would that indicate that I've gotten it too hot and the inside of the circuit may be damaged? I don't know how to get precise readings on my multimeter, but now I'm getting between 3 and 5 with it set on RX10 when I touch just about any two points on the LCD, which makes me think that I've ruined another one.

Edit - Actually, I might just be a stupid head. I said "about any two points", but all I was doing was any point and ground and that might be okay, right?

I just put it back in the car just for grins and it is still behaving the same in the car as before. It is trying to show me instant and current mpg, but it is doing it with half the screen inoperative and the other have uncontrasted so you have to look at it at an angle.

[dcb]

Well, you should be able to stumble on a contrast that works, like wyatt mentioned. Just hit left+right then in the setup screen hit middle till you can read it good.

Then feel your way over to the OK "button". If you go all the to the left character, then quickly but carefully hit the left button twice you should be there. quickly as in press and release the button quickly, but wait a 1/2 second before the second press.

Then do that for all the other settings and see if the contrast stays ok at least.


Test continuity between all points. Except for LCD 1,5,16 they should be about 10k or more apart. Send a pic of your ohmeter if you like.

[Axaday]

Originally Posted by dcb

Well, you should be able to stumble on a contrast that works, like wyatt mentioned. Just hit left+right then in the setup screen hit middle till you can read it good.

Then feel your way over to the OK "button". If you go all the to the left character, then quickly but carefully hit the left button twice you should be there. quickly as in press and release the button quickly, but wait a 1/2 second before the second press.

Ok, I was aiming for ONE left of the left character. I'll do better in a few minutes.

Test continuity between all points. Except for LCD 1,5,16 they should be about 10k or more apart. Send a pic of your ohmeter if you like.

I don't know what I was thinking in my last edit. Of COURSE it isn't okay that every pin is showing some continuity with ground. Even the power wire is doing it. I think I've melted the circuits inside the LCD with too much soldering.

If it is giving me calculations and running through the setup screens, does that pretty much indicate that everything is sound except my LCD? Is there an LCD out there that is going to be easier to install for a hamhanded solderer like me?

[dcb]

Of course you have the power unplugged when taking these readings?

[Axaday]

Yes, unplugged it is showing an alarming amount of connectivity. I think I'm reading right that nearly every pin, including the power, has only 30-50 ohms of resistance to ground.

Going TWO left from left worked. It saved my settings. Which means I COULD start using it. It appears that I can read the instant and current MPG without the other half of the screen. But do I run a risk of damaging the computer with all of those pins grounded? Would it be a lot safer to wait until I can get another LCD?

[dcb]

I think you have to look somewhere else than the lcd, this is your second one no? Same symptoms?

The meter is on x10 and not x10K ?

[Axaday]

Originally Posted by dcb

I think you have to look somewhere else than the lcd, this is your second one no? Same symptoms?

It is my second LCD. But the symptoms aren't quite the same. The first one put white blocks on the right side of the screen and left the left side blue. This one showed while blocks all the way across until I got the contrast adjusted and now it works right on the left side and has white blocks on the right side.

The meter is on x10 and not x10K ?

Yes, Rx10. The only non-ground wire on the LCD that isn't showing around 30 ohms from ground is 15. I can't think how that could possibly be other than the LCD being damaged.