No display on MPGuino LCD, just backlight
 

Quick history: I got my MPGuino assembled, and had to change the 7805 voltage regulator.

Sometime during the process of desoldering the LCD and resoldering I must have messed something up...

With the new 7805 the gauge worked, however I had intermittent freezes... Not constant just 1 per trip whereever I was going...

Well, the last time I used it the screen went blank. I had a backlight so I knew power was still getting to it.

I hooked it up to my computer and still the same thing - backlight, but no characters at all.

I touched the LCD and I saw the normal display, moved it and it went away.

So, I had placed a spacer in between my 2 boards, so I took it out. and the display stayed. Unless I moved the LCD a little.

My next step was to desolder the LCD again - and snug it onto the header, and re solder. Well, I couldn't separate the board, but I had all the solder off of it... I resoldered, and now I all I have is a backlight display with no characters....

I checked continuity between all 16 pins on both sides of the board, and it was good...

I ohm checked all 16 pins through both sides of the board. All read good.. 0.00 ohms.

So, I'm at a loss. It was working before I de and re soldered. It's like a line or pin broke which delivers the info to the LCD, but all the pins check good... Any suggestions would be welcome...

Ive had the backlit screen with nothing on it, but that always meant the chip lost the program. And that was happening from low voltage problems, or from touching the wrong part of the board with sweaty fingers. You could always try reflashing the program just to make sure it is there.

If it still doesnt work, it does sound like a connection problem. Maybe one little piece of solder that is bridging two pins.

I know this might sound silly, but is there a link to idiot proof re flashing instructions?

Did you mean re flash the sketch? or re load the boot loader, both of which I'm trying to figure out...

I downloaded the Arduino v 0012 Alpha and copied the sketch off of the link from spiffie's website, and verified the sketch but it said the sketch was too big... So, I'm digging and digging for more info - anything that can save me some time would be great :)

*oops* just read the top of the sketch and saw that I'm suppose to be using Arduino v 0011...


** Alrighty** I downloaded v 0011 and I uploaded the current sketch... No change..

I am able to change the brightness on the screen, just still nothing but the backlight... and the backlight does time out after the preset amount of time... whatever it was before... So... I guess I'm going to desolder the LCD again and do some examining..

I meant reflash the sketch.

dcb showed me once how to do the bootloader and make a cable when mine was acting up, but I didnt need to do it. Even he said that doing the bootloader took "a cable and some patience". So I would only try the bootloader as an absolute last resort.

Another thing I found is that you (or at least I) can only have one file in the computer with the pde extension, and I keep it called mpguino.pde. I normally keep one saved with the default settings for each vehicle. I have to give these others a txt extension, or it will give an error and not load the sketch.

Yes the wrong version of Arduino will cause problems. I would deal with that first.

Well, I think I figured out the problem. Possibly.

I'm going to share my screw up with everyone because I learned a valuable lesson, and I'm pretty sure this is the source of my problem.

The first and second time I desoldered my LCD I used a common screw driver to pry apart the boards, because I didn't desolder them correctly.

And when I did that prying I put divets in the board...

Now, I didn't know that the signal line from the atmega runs along the outside of the board so I didn't know my screw driver was going to cause any real damage besides superficial...

So, here's a picture of the damage... For anyone who doesn't know - DO NOT use a screw driver to pry apart circuit cards!

For everyone else, - please feel free to laugh :)

So, now I guess a fix would be to solder in jumper wires to send the signals over to bypass the damage I did... Time to study the schematics I suppose..

I checked continuity between Pin 13 and the small ring by the 2 pins that it looks like that signal goes through, and I had good continuity, so my guess that the divets I made in that line was wrong...

So, I soldered the LCD back to the board, and still no change...

I did re flash the sketch before-hand with no change...

So here I am, no idea where to go next. Besides desoldering the LCD again and investigating some more...

I was wondering if anyone could tell me the pins on the atmega that deliver the digital display data to the LCD header?


I understand that Pin 1, 5, and 16 are ground on the header for the LCD.

I need to know the digital data Pins on the atmega to the header so I can solder in jumper wires in case I did damage the board.

I know my MPGuino still has functionality, because I can still adjust the brightness on the LCD and if I push buttons randomly it seems like I'm changing settings, because I push buttons and I can't change the brightness until I replug power to it.

So - my theory is - it still has the program on it, all connections are good except digital display data going to the LCD.

If anyone can point me in the right direction as far as getting the right pin or pins to jumper to the right header pins I should be able to get fixed. Thanks!

here is the arduino based mpguino schematic:
http://opengauge.googlecode.com/svn/...ino/wiring.GIF

and here is the actual chip pin mappings:
http://www.arduino.cc/playground/upl...168PinMap2.png

so you should be able to determine what pins on the atmega should be connected to what leads and which ones they shouldn't be connected to with that info and lots of probing with a voltage meter.

Thanks Dcb! I saw the schematic, but not the pin mapping for the atmega. I appreciate it!

I've done continuity checks and ohms checks between the atmega pins and the LCD and they all check good as well.

Could it be that I hosed up the atmega?

Did you check for cross wiring? I.e. put the ohmeter on lcd 16, and make sure there is no connections where there shouldn't be?


Just for comparison, I did and most of the connections were separated by at least a megaohm, except the following:

LCD pins 1,5,16 all connected.

LCD pins 2 and 3 were seperated by about 10k ohms (shrug).

notes:
unit unplugged
I put ground on LCD 1, then touched positive probe to 2, then 3 ... 16 and noted ohm readings.

Then I put ground on LCD 2, then touched positive probe to 3, then 4 ... 16 and noted ohm readings.

Then I put ground on LCD 3, etc.

I checked for cross wiring. None present except the ones that are suppose to be.

1, 5, 16 are all connected.

I'm going to jumper all signal lines straight from the Atmega to the LCD pads when I get some time..

I'll do it 1 at a time so if I fix it I will not have to do all of them.. shouldn't be too bad, since all 16 pins are not signal lines.. I won't do power or ground, and I know there are several that aren't used.

I think I found the problem.

I desoldered the LCD again in preperation to jumper atmega pins to the LCD pads.

I looked at the back of LCD and noticed Pad 3 had some missing gold on the back side of the pad - here's a picture.

I did some continuity checks between the pads and the little holes directly behind the LCD and there was no continuity between pad 3 and it's corresponding circuit run to it's tiny ring...

On the spiffie schematic pad 3 is labeled as CONTR - it is recieved from the atmega... That would explain why all my continuity checks from the atmega to both sides of the header pin were good, I didn't check the back side of the LCD to their final destination..

What do you guys think?

good eye :) I'd blob some solder on there.

I tried blobbing solder on there, but it wouldn't flow all around the pad...

So, I ended up putting a jumper line between the little ring for pad 3 and Pin 3 on the other board... Continuity checked good, so I tested it out..

Still didn't work. Needless to say I did fix a problem. Just not the right problem.

I'm concerned that If I de solder that LCD too many more times I'm going to need a new one.. The pads are starting to deteriorate..

I'd like to fix this problem, so if anyone else has it they'll be able to learn from my mistakes :)

So, my next step is to go ahead and jumper wire all the atmega connections to the pads on the LCD by-passing the header.

I'll still have the header soldered in, but just in case a pin is broken the jumper wire will by - pass it... Unless anyone has a better idea - it's the best I can come up with.

dcb - thanks for the encouragement - I might end up buying a premade MPguino from you if I can't get mine fixed, it would be a shame not to use the wire's I spent hours tapping into my car (tapping, routing, etc)..

Here's an update!

I desoldered tonight tinned all my jumper wires before de soldering...

I soldered all 6 ( I already had the contrast on ) wires on the back of the atemga, I labeled them and my contrast (the one I had on there already ) broke off, so I thought great - good thing I tinned an extra wire, I'll just have to replace it..

I looked a little closer and found out I had put my contrast jumper wire on the little ring for pad 4, not 3....

I was PISSED. So - I was SOO sure that I found my problem I DE soldered all the jumper wires I had soldered and labeled on the back of the board.. I had yet to solder the other side to the LCD..

So, after taking out all my jumper wires - I re soldered the LCD to the board - put a new jumper wire on the head 3 pin and soldered it onto the top side pad 3.

SO.. Now I have a display.... YEAH... BUT... It's the top line of all blocks..

I re flashed the sketch - no change... - I did find out I could adjust the contrast and the brightness - but the solid top row of blocks is what I'm adjusting with the contrast...

somebody shoot me.. :)

Anyone have any ideas about this new problem I have?

All blocks on top row of LCD - nothing on bottom row, brightness and contrast is adjustable.

I also did the serial check while it was hooked up to my PC and the 000.0 was scrolling in the Arduino program..

I am also able to upload sketches, but nothing changes whats on the display.

I did search through the forum for "blocks" but the other block problems did not seem like what I am experiencing.

Can someone tell me at least from the symptoms of what I've got if my atmega is still good or a bootloader got dropped.. I imagine if it did I couldn't load the sketch right? And the serial monitor wouldn't put anything out right? I mean I really don't know.

Can you get a voltage reading at the 5V power wire to the LCD? Pin 2 I think. That would at least tell you if you have any voltage issues. Mine would act up with anything below 4.9 volts and sometimes would show blocks on the screen, or clear itself, or restart, or lock up. I have read of quite a few others showing just blocks on the screen, for various reasons.

wagonman - I haven't checked to see what my voltage is on pin 2 of the LCD, I will though.

I'll take a look tonight before I desolder.

I did see several posts about blocks on the screen, perhaps I missed the one that was identical to my problem. *shrug* I'll look again.

Well - Here's my verdict.

I de soldered - re touched every solder connection that might have been considered grey - made a plastic backing for my LCD - resoldered everything because I thought maybe it was just the contact between boards -

And it still had blocks.............

wagonman - I did check pin 2 with power on - 5.06 v solid... So power was good I believe.

So - I desoldered again. Pushed all the pins down - removed/cut pins 7-10 off. Did not get the plastic off (I was to anxious to see if the new stuff worked). I cleaned up the remaining pins.

I recieved my NEW LCD today - blue background/white letters - made another plastic backing - soldered it into place - a bit more space between boards this time...

Plugged it into my car - and It WORKED!! HOT DOG!

It came up with Ver .74 - so I know I was re flashing the sketch correctly all those times. :) Mine shipped with ver .73 when I initially powered it up.

So, Either pushed the pins and cleaning them up solved the problem / or my LCD was toast... Considering all the times I've soldered and desoldered that LCD who knows..

Thanks gascort for sending your MPguino to dcb - thanks dcb for giving me 1 more thing to try before I stomped on my MPGuino :)

Hey - dcb - if you want I'll mail you my LCD if you are curious. I'm done soldering for a while.

5.06v is great. Who knows, it could have been either problem you mentioned. But at least now it sounds like youre in business.

Oh yeah! In business indeed - I'm pretty sure I could have used the other side pads on the LCD (run jumper wires from the header pins to the other side) and it would work, I might try it later if I get REALLY bored :)

I did some through hole continuity checks on the old LCD, and I had a few more pads that did not have continuity through them, but all the pads on the opposite side of the LCD were good... *shrug* I won't throw that LCD away for now.

Well - after 40 miles - not a hick-up. Solid as a rock!

It's a shame that besides the bad voltage regulator, that all my other problems were self induced :)

i now have this problem. but its different. mine was working before as you all have seen. i still can cycle through all the brightness levels. and if i tilt my screen at a very sharp angle, i can sorta read the display. anyone have an idea of what the problem could be?

bah damnit. nevermind. its working now. something must be loose. damn. well i kinda dont want to yank it apart unless it happens again. the case i mean.

Can you adjust the contrast at all?

yea i could. i got it working now. electronics are funny on operation. and im an electronic tech..... a mystery in life....

Anything in particular you did to get it working?

i figured out what happened the first time. i had it plugged into a hub that wasnt powered. powered the hub, and the display lit up light it should.