Wapata

CORE_STM32F4 Module, LCD, and fire

38 posts in this topic

Hi !

It may be because English is not my native language but I have to say : The LCD part of the CORE_STM32F4 Module page is not clear at all. Because of that (and because I didn't take the time to check the VCC and Ground BEFORE soldering) my LCD have made this typical sound of... fire starting.

I have followed this page: http://www.ucapps.de/index.html?page=mbhp_lcd.html / MIOS32 Connectivity / Wiring Diagram for 2x16: mbhp_lcd_mios32.pdf (as my LCD have all the pins in line).

But after that... the wire 3 is NOT V0. So the sentence "Order of wires is matching with flat ribbon cable" doesn't work. And I can't figure out how it can work (with the J15 port at his place). For me all the wire have to be twisted two by two. It's too cold is the garage right now, i will try tomorrow.

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17 minutes ago, Wapata said:

the wire 3 is NOT V0.

What do you want to say ? I don't understand.

Did you check the pinout of your LCD first? Model/brand.
Please share all information, picture maybe, Core + Ribbon +LCD.

When you say "fire starting".. Is it burnt? Really!? You've got another one?

Best Bruno

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Multimeter in "bip if wire" position. V0 is not in the wire 3 but the wire 4. Sorry I didn't check my messages before posting (baby things to do...) And forgot to mention it.

Yeah the pinout of the LCD is very clear and written on the PCB. The problem is one the other side, as I have the big black plastic of the ribbon port that hide all the important information written one the core PCB. Had to remove it to check... After the fire.

The LCD is probably dead (in French: le son (juste le son) d'un petit feu qui crépite est mauvais signe, la nouvelle odeur aussi, mais je testerais le nouveau câblage... Au cas où) but yes, I have an other one ! Lucky me...

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Aha, the magic smoke release!

The rite of initiation!

We all went through this, some people like me even multiple times, with back then superexpensive OLEDs :)

Welcome to MIDIbox! :-)

(I think you might have installed the cable in reverse thus swapping a few pins around)

Many greets,
Peter

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Posted (edited)

1 hour ago, Wapata said:

V0 is not in the wire 3 but the wire 4

Ok this is not the cause of "the new smell" cause you just send a voltage between 0 and Vdd to the RS pin. sending core RS Pin to LCD V0 is worst, hope it's your LCD which smells not your core.
Try another LCD and check all wires this time, check also for short circuit between adjacent pin if you've got the time and you're not sure of your ribbon. A bad crimping happens to me recently ;)

 

1 hour ago, Hawkeye said:

Welcome to MIDIbox! :-)

Yes! Welcome to this new world of sound... and smell lol

Edited by Antichambre

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Posted (edited)

Thank you both of you ! In fact I'm an old newbie here. My core was made in 2016 (edit: the metadata of my pictures says October 2017), and I follow uCApps for more years than that ! Maybe 2004 (... Wow.. so long ?..).

It's okay for me to broke an LCD, but the point here is about the indication on the website, they are confusing about the ports of the STM32F4. I mean... Really. 

But on the other hand, I should have double checked the vcc and ground for sure.

Edited by Wapata

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Just now, Antichambre said:

sending core RS Pin to LCD V0 is worst,

Oh.. I think I did that, if wire 4 is V0, then wire 3 should be RS !

(Wire 1 and 2 swapped, 3 and 4 swapped, and so on)

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Just now, Wapata said:

(Wire 1 and 2 swapped, 3 and 4 swapped, and so on)

That sounds like a cabling issue to me. You probably crimped the cable the wrong way round (or used a cable that was crimped the wrong way without you noticing).

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Did you connect the IDC16 cable on the top or the bottom of the display?

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Ah right, these can be very confusing! Also, the way CMOS labels power connections as Vcc Vdd Vss etc. can also lead to mistakes.

I didn't check the pin compatibility (please check!), but this PCB might help:

 

 

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It look MIOS8 compatible, not MIOS32. But the idea is cool. With 90° pin header the PCB + LCD + Cable will be "flatter" .

I have to reinstall eagle and sketch the idea ! Thanks !

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I'm back from the garage. It's -1°C ... cold. Anyway here is a google album with the pictures i have taken, just under the midi-notes attribution chart: https://photos.app.goo.gl/5bR4r2ivZe5dgYYW9

You can see where is the notch of the ribbon head, the big clear labels on the LCD PCB, the labels hidden under the "big black plastic of the ribbon port that hide" and finally, how I test and found where the V0 is.    
Please not that I've tried to de-crimp the ribbon yesterday, but it was well crimped before the incident.

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We can clearly see on your pictures that VDD goes to ground(Vs) and VSS to Vd, just follow the red stripe !
In fact, I think all is reversed by pair! You have to unsolder the ribbon on lcd side and solder wire 1(red) to pin 2(Vd), wire 2 to pin 1(Vs), wire 3 to pin 4(RS), wire 4 to (V0)... et ainsi desuite...
 

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When you look at a male IDC pinheader from the top, the pins are numbered 

 ________________________
|02 04 06 08 10 12 14 16 |
|01 03 05 07 09 11 13 15 |
__________----___________

 

Because we normally connect displays on the rear side, the Core J15 is mirrored, so it's actually

 ________________________
|16 14 12 10 08 06 04 02 |
|15 13 11 09 07 05 03 01 |
__________----___________

 

Thus the pin numbering starts at 01 in the bottom right corner.

Could you check that these pin numbers correspond to those on the LCD when the cable is connected (with the power off)? Or are the pairs inverted as Bruno says?

Otherwise the pinning on the LCD (unless it's mislabeled) looks to correspond to the Hitachi standard. 

 

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Posted (edited)

7 minutes ago, Antichambre said:

I think all is reversed by pair! 

Yes, this is what I think and write earlier. That the first reason why I'm in this particular sub-forum... There may be something really unclear about the "mirror" thing on the documentation page.

Just now, latigid on said:

Could you check that these pin numbers correspond to those on the LCD when the cable is connected (with the power off)? Or are the pairs inverted as Bruno says?

The multimeter as show say "it doesn't". The V0 "bip" on the wire 4.

And yes it is like Hitachi 

Edited by Wapata
Was on my phone, couldn't suppress code.

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33 minutes ago, latigid on said:

Because we normally connect displays on the rear side, the Core J15 is mirrored, so it's actually


 ________________________
|16 14 12 10 08 06 04 02 |
|15 13 11 09 07 05 03 01 |
__________----___________

 

It doesn't look true... Here is what happened when I clamped the ribbon (with V0 at pin number 04) :

 ________________________
|15 13 11 09 07 05 03 01 |
|16 14 12 10 08 06 04 02 |
__________----___________

And I can't mechanically change this order can I ? The red strip of my ribbon will always be clamped to the top right of this schematic (The last wire will alway be at the bottom left too).

The two opposite side of ribbon cable will alway be in diagonal, top right / bottom left as i understand. Did I miss something ?

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Just now, Wapata said:

And I can't mechanically change this order can I ?

Sure you can, you have crimped the connector to the cable the wrong way round. There is a little marking in the form of a triangle on the connector - this should match the red wire, as it marks pin 1. It looks as if you have ignored this.

That's what I already suggested above.

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Oh I see the triangle in the first photo ! I did miss a big I formation then, thank you ! Is there a page with ribbon tip and tricks ? 

And sorry that I didn't understand you the first time. Language barrier maybe ;-)

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Posted (edited)

16 minutes ago, Wapata said:

And I can't mechanically change this order can I ?

Yes you're right you can't do it on the ribbon with the IDC!!! for sure!

10 minutes ago, ilmenator said:

Sure you can, you have crimped the connector to the cable the wrong way round. There is a little marking in the form of a triangle on the connector - this should match the red wire, as it marks pin 1. It looks as if you have ignored this.

That's what I already suggested above.

No the only way is to put the header on the rear side of the core pcb...

Then @Wapata  just swap the pins by pair on the LCD side, like I said before and everything will be right, and you're right there's a mistake on the diagram.

Edited by Antichambre

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Posted (edited)

Usually we mirror the pairs by putting the header on the rear side of the LCD, this is the only way but it's only for 2 row connector on LCD side, for an inline connector on the LCD this is not possible, then pairs have to be swapped on the LCD.
Simple!
You can turn the IDC on every way, pin 1 or 16 will always be on first or last wire of the ribbon!!! Clear? ;)

Edited by Antichambre

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Clear to me ! Thanks a lot !

Lesson learned : check, double check, triple check before power up !

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42 minutes ago, Antichambre said:

You can turn the IDC on every way, pin 1 and 16 will always be on first and last wire of the ribbon!!! Clear? ;)

That's true, my bad! The mixup happens when soldering the connector to the wrong side of the PCB.

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