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lcd problems


supraanimo
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Hi,

I recently finished my midibox core after solving many problems already and everything seems to be working fine, except that the recently attached lcd module does not work except for the backlight.

I sent the query string to the lcd :

F0 00 00 7E 40 00 0D 02 00 0B 0A 00 00 00 01 00 00 00 00 F7

and received back:

F0 00 00 7E 40 00 0F 04 00 F7

Can anyone tell me what is wrong?

I am running a tianma display module with a ks0066u controller, display model tm402cd.

Thanks

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  • 4 years later...

Hi,

same problem here.. LCD lights up, shows the control characters in the second row, but no READY msg and no initialization string from my app.

I sent the same sysex as  supraanimo and got the same response...

Looking at the pins, i see no evident shortage..

Thanks in advance

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Heya demym,

Firstly - you should start new threads more often. I've had to move one of yours already today because it was OT/hijacking, and this one is resurrecting a 5 year old thread. Best to just link to it, in that case.

Anyway, we need more info. Pleas see the link in my signature labelled 'troubleshoot'. Include as much info is relevant:

Did itwork with a different app installed? What core? what pic? 4bit or 8bit? etc etc etc. Please include the results of all your troubleshooting.

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I tried it only with my app (which is a simple midi processor/filter, only Core V3 with PIC18F452).

(but i don't even see the MIOS..ready message, only a bar in the second row).

The display is a YM1602C, i've checked the datasheet but have not seen nothing strange (also, i'm not that sure that i understood it...)

I really don't know if i'm using it 4 or 8 bits.

In my program i have:

code in DISPLAY_Init:

  MIOS_LCD_Clear();

  MIOS_LCD_CursorSet(0x00);

  MIOS_LCD_PrintCString("OK App ready");

and the usual stuff when calling display:

MIOS_LCD_CursorSet(0x00);

MIOS_LCD_PrintCString("PC Swap: ");....

I've checked the pins and they seem not to be shorting..

Sorry for posting to old messages, as i'm a novice i thought it would be better that posting many new topics, as help is often needed at beginning.

Anyway, i will post new threads next time.

Thx

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Yeh nothing to stress about or I woulda moved this one too :) Just lettin' ya know for next time. Anyway, down to the more important stuff...

If it's a '452 wired in the normal manner, then it's 8bit... but if you don't even see 'READY.' then something ain't right (and you definitely should not have started uploading apps). Firstly I'd upload a fresh copy of MIOS (In smart mode, wait for upload req=on) and see how you go.

I get the impression that it seems to be responding to MIDI.... After you upload MIOS, if you still don't see anything on screen, you may want to try uploading another app for testing - but not yours. Use a known-working app, like MIDIO128 or ain64_din128_dout128 or something. The idea here is to see i the core is actually alive and responding, other than the LCD.

All that said, this is almost certainly a soldering error, so I would get my multimeter and the schematics out and triple-check the wiring.... Perhaps the nonworking LCD is a symptom of another problem that could cause permanent damage. Best to be sure and spend a while to check it. As you've already checked for shorts, I'd be checking that the correct wires are connected. For example I wonder if you've got the enable line wrong?

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Sorry to stress once...

But i really have no luck with LCD... I've checked connections (and they seem to be correct), shorts, rebuilt the cable.... but still

getting the 16 blocks on the second line (it's a YM1602C 16x2) on powering up the core, and nothing more.. no Ready msg.

I uploaded only MIOS (not my own application), and it is running fine, as i get the sysex message on power on... With my application it was running fine too (i built a midi controlled looper with a separate relay board with ULN1803, and relays switched correctly on and off, using J5 as DOUT)..

I think LCD should be fine, as it is shiny new... but really don't know how to test it without the core, never dealed with an LCD before.

Don't know where to look anymore... i think i will do without a LCD (but i really built the core to have the LCD :-) )....

I'm sure that core is running fine, with MIOS, and with MIOS and my application..

Just for your info..

Thanks anyway.

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Hi.

Looking at the datasheet for the YM1602C, it looks pretty standard. If you have a line of 'block' characters then this usually means that the display is receiving power but has not been initialized. This would indicate a wiring problem.

The display supports both 8 and 4 bit but unless you are using a PIC18F4685 (which you say you aren't) then the default will be 8 bit.

The LCD display type can also be selected by programming a different PIC ID, by default the ID is 0000000000000000 and unless you requested a different one (I take if you bought it from SmashTV or Mike) then the default is a character LCD.

I know you have checked it but I would definately suspect a wiring problem, the fact that you are getting anything on the display means that it doesn't look like you have mirrored the connections  :)

Looking at http://www.good-lcd.com/upfile/product/2008920163018106.pdf the wiring should be exactly as on the wiring diagram http://www.ucapps.de/mbhp/mbhp_lcd.pdf so I would suggest a multimeter/continuity tester and double-check for shorts etc. I would also check right back to the PIC itself as a dry/bad joint might be the culprit!

It is also possible that the LCD is faulty but you would really need either another Core or LCD to really verify this!

Cheers

Phil

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When i upload MIOS you mean ? Well, i leaved the DeviceID=0 and Bankstick=1 (i have no bankstick, but it seems not be possibile to set it less than 1).

Is this the default situation ?

In the meanwhile, i'm trying to check LCD in another way (building one of those modder little circuits to attach the display to lpt1 on pc and see if it works with one of those LCD management softwares).... If only i didn't have to desolder all those cables... :-)

Thx, have a nice time

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When i upload MIOS you mean ? Well, i leaved the DeviceID=0 and Bankstick=1 (i have no bankstick, but it seems not be possibile to set it less than 1).

Is this the default situation ?

Yep, that means you're on ID 0 which is CLCD. That should be fine.

In the meanwhile, i'm trying to check LCD in another way (building one of those modder little circuits to attach the display to lpt1 on pc and see if it works with one of those LCD management softwares).... If only i didn't have to desolder all those cables... :-)

Great idea! But no need to desolder anything at all, just disconnect the IDC connector from the core, and make an LPT->MBHP cable converter thingy.

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  • 3 weeks later...

Uhm...

so i bought TWO new LCDs !

The first one didnt' work at all (only backlight)... then  i bought a third one (same as the first, YMC102, with the same datasheet)..

I still get only blocks when powering on the Core.... (but didn't still connect the d0-d7 data lines, only to test LCD functionallity)..

I've noticed something strange: i constantly have 5V on V0 of J15 (LCD), regardless of the position of the contrast pot...in fact, i get the white blocks only when shorting to ground the corresponding pin V0 on the LCD.... i did triple check on my core solderings.... could it be that the trimmer is out of use ?

Also, the luminance pot seems not to be working either: it should work even if i connect only the two backlight pins, right ?

I got J5_IO functioning (both for DIN and DOUT), the core is responding to miosstudio, the application works fine, the relay board works nice....... only i would like to see, someday, that famigerous READY on the LCD !!

Going to check once the solderings (and i found two of them that weren't perfect, but nothing changed).... but i'm really depressed without my LCD...

Thanks anyway

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I can offer a few details:

i'm trying to check LCD in another way (building one of those modder little circuits to attach the display to lpt1 on pc and see if it works with one of those LCD management softwares)....

Newer PCs power LPT1 at less than 5 volts, It's not a reliable way to test a display. Good thinking though!

I still get only blocks when powering on the Core.... (but didn't still connect the d0-d7 data lines, only to test LCD functionallity)..

Huh? Two thoughts..

If you're getting blocks on the second line only, then it sounds like a good display that's not getting signals. If you're getting solid blocks on BOTH lines, it may well be a contrast problem. SOME displays require a negative bias to get the display visible. Check your data sheet.

How can you test without connecting the data lines? That's a guaranteed no-go. There is NOTHING in the display that will say "Ready" or anything else. That comes from MIOS, and it will require connecting R/S, E, and either 4 or 8 data lines to the display.

Good Luck, I'm troubleshooting a display problem here tonight, too. Sometimes it's just part of the process. :-)

LyleHaze

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SOME displays require a negative bias to get the display visible. Check your data sheet.

What does a negative bias means ? this LCD has white characters on blue blackground, and it's pins (from its datasheet) are disposed as in the MBHP building an LCD cable pdf... is negative bias something else to look for ? didnt' find that words into the datasheet.

How can you test without connecting the data lines? That's a guaranteed no-go. There is NOTHING in the display that will say "Ready" or anything else. That comes from MIOS, and it will require connecting R/S, E, and either 4 or 8 data lines to the display.

I know i will not see Ready until i connect all the lines and the pins... but for now i'm stucked into the V0 contrast problem (got 5V constantly on that pin, regardless of the contrast trimmer position, ...)..i only see blocks when shorting to ground V0 pin on LCD. But also luminance trimmer doesn't do that much.. it should work even with only backlight + and - connected, right ?

Thx, Good luck for you lcd problems either :-)

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OK, I looked up your datasheet.

It looks like that one should not need any negative voltages.

The datasheet calls for a pot from VDD to VSS, with the wiper connected to V0.

The core schematic shows exactly that for the V0 connection.

Contrast pot: P2

So.. check the contrast pot on the core: One end should read +5Volts, the other end should be grounded.

The voltage on the wiper Should move between 0 and 5 volts as you turn the pot. This should be connected to V0 on your display. On the Ver 3 core board, this is the pot furthest away from the display connector.

http://www.ucapps.de/mbhp/mbhp_core_v3.gif

Luminance Pot: P1

Not necessary to get a working display, I'd leave it alone until everything else is working.

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I still get only blocks when powering on the Core.... (but didn't still connect the d0-d7 data lines, only to test LCD functionallity)..

i bet u have a short somewhere...

check the exact wiring...

disconnect everything and unsolder the Display connector of the core...

clean the pcb around that area and check with multimeter for shorts...

again solder the pins or wire, and check once again for shorts on that area...

then connect only one display... and see if it works...

u mentioned to have many problems...?

who are u telling this, even now after i have finished everything.. i connectet yesterday the bankstick,

and now something else is not working...

but from what i have learned during the hole construction process of this project, are wiring problems.

actually about every problem is relatet to bad wiring and shorts...

trust me

so just take a break... unsolder the parts, clean it up and do it again.

u cant do anything else, i had the same problems

it took me 3 days to work out the display issue... there was a short on the core somwhere around the display port

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