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grahamg

Problems with CORE module...MIDI-

15 posts in this topic

Hi,

I just finished assembing the core module and am having problems trying to load MIOS.  I tested voltages across the important IC 1 and 2 pins and got nice steady 5V.  I was also getting 2 nice rows of black blocks on my LCD, presumably indicating that the bootloader was loaded on the PIC properly.  Next I hooked up the midi box to my PC, booted up MIDI OX and tried to upload MIOS 1.7 via the bootstap loader.  This was not successful and after scratching my head a bit I tested the IC voltages again.  

Not only does the LCD not show anything now, but IC 1's pins are dead!  I get NO potential across connections: IC1 (1)-IC1(12), IC1(11)-IC1(12), IC1(31)-IC1(32).  IC2 is still showing steady 5V.  

What could have happened?  I have no idea how to determine what component could have died.  I could *really* use some help; getting pretty frustrated....

Thanx,

G

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Have you used a program like MidiOx to be sure that you are getting the sysex string from the core?

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Yes I'm using Midi OX to try and upload MIOS, but I'm not getting any response from the core at all.  

When I power up, my LCD has two bars of black squares for about 2 seconds after which it goes completely blank.  

I tried replacing the optocoupler, but still no luck.  

One thing I'm not sure about is the jumpers on the board.  They should all be on for uploads and all off for normal use, right?  

Any suggestions are *very much* appreciated.

Thanks,

Graham

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The jumpers must always be on !

The intention of this connector was a in-circuit-programming of the bootstrap loader on the pic.

So put the jumpers on and go on ...

Doc

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Thanks for the reply, Doc!

Jumpers are all on and I've got communication between MIDI-OX and the core now (had wiring reversed on MIDI OUT pins, stupid me!).  

Now I've uploaded MIOS 1.7 which I think is working properly since it echoes F0 00 00 7E 40 00 0F F7 when I send it.  However, I don't get any random events in MIDI-OX after starting up the core.  Shouldn't the PIC be sending out random readings from all the 'ghost' connections?  When I boot, I get black squares on my lcd for 2 second (bootloader) and then it goes blank.  I also only get the one single 'ready' sysex message and then nothing else.

I've tried uploading all kinds of apps, but the behavior is the same.  Shouldn't my LCD display something after the black bootloader blocks?  Its a 4x20 HD44780-based display that I got on ebay.  

BTW, my PIC ID is all 0s.

Please help me out here guys, I've read through everything on this site and I'm pulling my hair out trying to get this thing working!!!!

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Ok, sounds like you have a problem with your LCD connection. If you have loaded midios and you get the sysex back, you should see a midios bootup message on the lcd followed by READY.  Do you have the contrast pot hooked up properly? Also, if only the bootloader were loaded, you would get those blocks, but they would stay on not turn off after 2 secs. double check all your connections to the lcd. The random midi events will ony happen if you have a MidiBox application that uses the AIN interface like MB64. If you load MB64E (encoders), or MidiBox sid, you won't get any.

Keep trying, you'll get it.

Justin

p.s. also check the pinning on the transistor. a lot of people get it backwards

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also - check into something that I just noticed myself - if the voltage going to the core drops below like, 5.5V then the LCD starts losing contrast. I had to crank  my lab supply to like 7VDC when building tonight before the contrast worked properly. Also - make sure your transistor is based properly, otherwise - HEAT! Good luck - Tim

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Hi Milkmansound,

(@grahamg -> this is not really a solution for your problem, just a generell advice !)

I also noticed this problem several times. If the voltage (after the regulator) drops under 5V the display is getting dark.

You'll notice this especially if you have more than one LCD with backlight connected.

The reason is mostly the behaviour of the voltage regulator. If it is getting very hot the in-circuit-protection of the regualator is reducing the current on the output (this is reducing the output voltage of course). So: Give your regualtor a cooler (not a fan, just a stripe of metal or a "finger-cooler" is enough in most cases). The rule is: If it is too hot to be touched it MUST be cooled. Otherwise you get a under voltage after a short time.

Without cooling the max. current of a 1 A regulator drops about 500mA !

The input voltage should be about 7 - 9 V, if you use a regulated DC Device. Thats right.

greets

DOC

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First, let me thank everyone for their comments.  Getting a MIDIBOX going for the first time (especially with limited electronics experience) can be a frustrating experience!  ;)

I completely re-wired my LCD and seem to have solved most of my problems, at least I am finally getting stuff on the display.   The problem now is that its mostly garbage.  Depending on what app I upload, I can sometimes make out what the text probably says, buts there are all sorts of weird characters mixed in.  For example, lcd7_clcd prints:

'Jgnno"Wornf#_"""

*C+"2226"V.Knosg

The first line is supposed to be 'Hello World', right?!

I've double and triple checked the wiring as well as checked for shorts with a multimeter since archived posts in the forum suggested these to be likely candidates for the problem.  I also tried re-upping MIOS several times...

Could it be a shielding issue?  I tried moving my test station away from any computers, fans, etc., but didn't seem to make much difference.  

Maybe the display is just shot and I should try a new one?

Thanks!

-Graham

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what is the complete reference of the chip? (hd44780***).

because there are other version that hasn't got the right font... I bought 2 2x40 on ebay last year with those "bad" roms, and had the same problem.

:-/

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I was getting garbage once - turns out the pins were shorting against the metal case I had it in when I pressed a button - is this is the case yet?

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Is it possible you have some of the datalines switched? That could definately cause problems like yours.

I don't think you should use the CLCD drivers. You should just upload a regular Midibox program, like MB64E.

Do you have your own programmer for the pic?

If so, I would erase the pic, load the bootstrap loader. Confirm that you are getting the sysex messages. Then load MIOS. Don't try to load anything else until you get the MIOS Boot up screen followed by READY.

You are using a regular HD44780 display, so you shouldn't need a special driver.

I see that the display you bought needs an Inverting Power Supply for the backlight. Are you running it with out the backlight? Either way, the luminence pins on the core shouldn't be hooked up to anything. That would be taken care of by the seprate backlight power supply. I would advise testing it without the backlight on until you get it running.

Hope this helps..

Justin

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I'm pretty sure that the data lines are correct, but will check again.  I just got the EL inverter for LCD in the mail yesterday and have tried it out, but am otherwise testing without it.  Am I correct in assuming that the brightness pot on the core should not work with this type of backlight?

Don't have a PIC programmer (got the PIC pre-programmed from SmashTV, but just ordered the JDM), so I can't try wiping the chip, although this sounds like a good idea.

I'm starting to think that the display is just busted; maybe I'll just bite the bullet and order a new display....

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Well, I rewired the LCD for the third time and voila, clean, clear, and sensible text!  This time I swapped out the entire cable and that did it.  I've been using IDC cables so I guess there must have been an internal short.

Now I can finally get crackin' on the rest of my design!

Thanks again everyone.

-Graham

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