Help with Display

[Pehr]

Hi!

I've recentrly built the Step A Midibox SID, but I can't get the display to work properly. It just shows a lot of weird symbols, letters and numbers. Not readable. I'll post a pic when I get home.

The boards are V2 I think (bought in summer 2005), but I have modified them so they´re up to date.

The display I'm using is a 2x20 OLED (PLED)-display, bought from http://www.fractronics.com/2x20oled_new.shtml (datasheet http://www.fractronics.com/P029-BL2002B.pdf ) and I've seen people with those displays before that are working.

I've also checked the connections with the CORE-module and they seem correct.

The files that I've uploaded to the midibox are a new bootstrap loader, latest MIOS, the main-file of the Midibox sid and the 6581-file. It seems to be working and I get sound from it when I play the virtual keyboard on the computer.

Do I need to upload midimon or any other files, or is there a setting I havent configured?

What could be wrong, do I need to buy a new display?

[stryd_one]

Hmm, if it seems to be working OK but just showing the wrong characters*, then it's probably the wiring to the core. Check it again, but only use the schematics, just to be sure....

*You can check this by hitting menu buttons etc, and see if the screen changes.

[Pehr]

*You can check this by hitting menu buttons etc, and see if the screen changes.

Something does hapen when I push the buttons and rorate the encoder, but It's the wrong characters :P

I have checked the connections using the schematics, twice, but I could do It again... ^_^

I've also checked for any shorted wires, but I've not found any.

[MRE]

I dont remember if MB uses the LCD in 4 bit or 8 bit mode. Either way, in order to configure and start an LCD, the micro sends control charactors down only 4 bits.

So, if the LCD displays anything at all, then it was properly set up. However, if its displaying strange charactors, then it is either A: rapidly resetting (usually caused by a CPU brownout [low core voltage]) Or B: the other half of the bits are mis wired somehow.

Example:

Micro connected to LCD in 8 bit mode (Plus 2 control bits). Micro will only use 4 bits at first to configure the LCD. This either is correct, or not. If there is a problem initializing the LCD, the screen will likey not show anything, and certainly not data that changes due to input from the user. If, however, the other 4 bits are misswired, then the LCD will get 'apparently' correct data. I.E. it gets a charactor code that corresponds to SOMETHING.. just not what it actually SHOULD be.

The other possability is that during LCD initialization, it is set to one data rate, and the core actually attempts to talk at another data rate? Maby... I dunno about this one.

So, double check the high bits on the connection. Check for brownouts in the core. Check that nothing is shorting the connector to the LCD. I doubt MIOS is configuring one data rate and talking at another.

Try disconnecting all IO boards from the core, and power up just the core and LCD. Or try powering the LCD from another source if its VFD or other high current demand LCD.

[Pehr]

Thanks for the answer! I'll check again for any wires in the wrong place.

btw here's a pic

http://bp0.blogger.com/_yLuzXJnw-D4/RcHqDlznsSI/AAAAAAAAAAk/s_eMXs8U9xU/s1600-h/PICT2243.JPG

[MRE]

Takes a few tries sometimes to get the 8x2 connectors sorted out.  And you say the data changes as you do things on the box? When it changes, does it stay stable or does it look like it resets back to that screen again?

Is the MB otherwise in stable operation?

[Pehr]

0k, I've got it working for a short while. Seems that it was pin #10 of the display that was floating.

Thanks!