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Displays not initializing after working for a while


EvilEvilEvil
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You should test another LCD.

+1, buying a spare HD44780 display (can be smaller than 40x2 characters) e.g. from ebay for a few $$$ makes total sense to test things. Disconnect everything else, install the MBSEQ firmware (or any other app or test app from the ucapps MIOS32 download section) and connect the new display to see if the core is working properly.

Many greets,
Peter

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9 minutes ago, TK. said:

I need some time to thing about how to support this issue remotely...

Best Regards, Thorsten.

It MUST be the discovery board. Everything was working fine and then it sat around for a few weeks. Maybe I put something on it or it got scratched or something. The Disc board is the only thing that hasn't been replaced!

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New Core, New LCD, New DISC. Wow... no idea what is wrong here...

...don't give up! My left wrinkled toe tells me, this smells like a power supply issue :-)

Can you measure voltages on the core, e.g. on the J15a/b display ports (display supply voltage)? Just use a multimeter and measure between pins Vd/Vs.
Which display voltage (5V /3.3V) is set on J15S? Can you exchange the USB cable (i've had bad cables with super-thin wires or bad connectors and had problems even with low current draw)?

Can you examine the micro USB port on the core module? It is not very sturdy, I managed to rip off two of them, maybe there is a fracture/connection problem on one of the power pins?

Good luck!
Many greets,
Peter

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Thanks for the encouragement Peter! I am about to give up :) (for now).

I'm getting a voltage of 4.74 on the LCD pins.

J15_S is set for 5v

I've tried everything. USB mini cables, Micro cables, different 5v wall power supplies. connecting directly to J2, a 5v 1A battery, a 5v 2A USB hub..

Edited by EvilEvilEvil
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1 hour ago, latigid on said:

Verify each of the intended connection points on J15 are made correctly with the display.
Check for shorts between the cable pins (can happen with misaligned header)
You are fiddling with the contrast and brightness controls each time, right?

What firmware is loaded on the Core?

Yes, changing the contrast and brightness often. My assumption is that if you can see the bars then you can see the regular OS display, correct?

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As explained above, the notch of the connector only matters when both PCB headers are keyed (allowing only one orientation). Considering putting the header on one end of the cable, the same pins are connected regardless of whether the notch on the IDC is "correctly" aligned with pin one (lower left as viewed from the top) or rotated about 180 degrees.

But in TK.'s example above, rotating the cable about 180 degrees at the display end will mean the backlight circuitry will be where the power rails are supposed to be and vise versa, and this is not good for the LCD in most cases.

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Hm, a few questions:

* what happens, if you turn the contrast pot? Do the solid blocks visible in the picture just disappear and fade to "nothing"?

* which firmware do you have installed? can you install the newest MBSEQ from ucapps (and make sure you use the stm32f4 branch)?

* do you "see" the core in MIOS studio and can you send commands to the just installed MBSEQ via the terminal?

* did you build this second core as a completely new unit, aka have you also installed a new stm32f4 module or have you just plugged the old stm32f4 module to a newly built MIDIbox core?

* if it is a new core, have you checked the orientation and proper installation of the 74hc595 and '541?

Many greets and good luck!
Peter

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Just now, Hawkeye said:

Hm, a few questions:

* what happens, if you turn the contrast pot? Do the solid blocks visible in the picture just disappear and fade to "nothing"?

Yes. the brightness and contrast work as expected

* which firmware do you have installed? can you install the newest MBSEQ from ucapps (and make sure you use the stm32f4 branch)?

I have midibox_seq_v4_094/MBHP_CORE_STM32F4 installed

* do you "see" the core in MIOS studio and can you send commands to the just installed MBSEQ via the terminal?

Yes, of course. This is all documented in previous posts in this thread (I know.. it's a lot of content ;)

* did you build this second core as a completely new unit, aka have you also installed a new stm32f4 module or have you just plugged the old stm32f4 module to a newly built MIDIbox core?

Ye, completely new as if I had never done it before. New stm32 with a new core.

* if it is a new core, have you checked the orientation and proper installation of the 74hc595 and '541?

Yes, resoldered both of them. Checked the pin orientation many times. Ordered more 595Ns, 541ANs and have a full bag of them now!

Many greets and good luck!
Peter

 

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Just now, Antichambre said:

Hello,

Maybe you already did it also? But Diagram + multimeter and continuity testing of all the tracks between the STM board and the LCD, Maybe :pout:

+1, it might "just" be a soldering fault somewhere in that area - can you photograph the core front and back (deinstalled STM32F4 module) in high res and post it here?

If you have access to an oscilloscope, you can check all data pins at the display, it should show activity on most lines arriving at the display during startup, interesting are the lines R/S, E and R/W... and if these work properly, check the data lines.

I assume that you replaced the display "one last time"? Smaller HD44780 test screens are really cheap on ebay, the current one could still be burned from the previous core/wrong polarity?

Many greets and good luck!
Peter

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4 hours ago, Hawkeye said:

+1, it might "just" be a soldering fault somewhere in that area - can you photograph the core front and back (deinstalled STM32F4 module) in high res and post it here?

I already did :hmm:

4 hours ago, Hawkeye said:

If you have access to an oscilloscope, you can check all data pins at the display, it should show activity on most lines arriving at the display during startup, interesting are the lines R/S, E and R/W... and if these work properly, check the data lines.

I don't have an oscilloscope. I've tested the pins some.

4 hours ago, Hawkeye said:

I assume that you replaced the display "one last time"? Smaller HD44780 test screens are really cheap on ebay, the current one could still be burned from the previous core/wrong polarity?

OK, I'll try another one. Then that's it for now. Maybe in some months I'll get encouraged to go back at it.

4 hours ago, Hawkeye said:

Many greets and good luck!
Peter

Thanks again

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One last question.

It was working. Is it possible that it would work (or appear to work) OK with the connection wrong? And then it burnt out? Otherwise this whole thing makes no sense. I never changed the orientation of the connections yet it worked, was legible etc...

Edited by EvilEvilEvil
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35 minutes ago, EvilEvilEvil said:

One last question.

It was working. Is it possible that it would work (or appear to work) OK with the connection wrong? And then it burnt out? Otherwise this whole thing makes no sense. I never changed the orientation of the connections yet it worked, was legible etc...

No, as you suspect, it could have never worked with the connection wrong. But, the display could have just failed at any time, or maybe there was some overvoltage input or electrostatic discharge at any point damaging the display controller. As you can really buy a test display for 3$ (16x2 or 20x2 is sufficient), i'd recommend to just do that, and that when you install it, you try to operate the core on a well known power supply, e.g. from your computer or a high-quality usb powerbank.

I've also looked through the thread to see high-res photos of front and backside of the core (without the stm32f4 module installed) and did not find them (but maybe i did not search good enough) - so, if you already have them, please upload them, if not, you'd need to take photos directly from above the frontside and the backside of the core (not from an angle), so we could look at it, sometimes, solder points can go bad, even if you think they look good and that you have checked them.

I know, these mysteries keep a lot of people here wondering, what is really wrong with the board, please be assured, that we'd love to see you solving the problem (and to find out what it was!)
Many greets,
Peter

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