4*20 LCD Problem

[manolo]

Hi,

we just built our first midibox64 system. At the moment we are using one din4x, one dout4x, one ain4x and the LTC.

The Display is an Displaytech 204B ( http://www.displaytech-us.com/pdf/char/204b_series-v12.PDF ) from Reichelt.

The whole midibox seems to work. We connected 8 switches, 8 pots and 32 leds. The Midi-Input Monitor from Midi-OX displays note on/off signals from the switches, the pots react in a normal way and the connected leds work.

BUT the LCD shows nothing as  two rows of black blocks. The contrast and luminance is setable from the two trimmer ( p1, p2 on the core ).

We used the JDM-programmer with  the "mios_bootstrap_loader_v1_1b.hex" file.

With the Midi-OX ( Vers. Midi-OX 7.0.0.365 ) we transfered first the " mios_v1_8.syx"- file and then the "main.syx" file from the midibox64_v2_4 folder.

We checked all the cabels and junctions and they seem to be okay. We think if  the contrast is setable, that the problem is not to deliver -5Volt to the Display.

We don't know what to do next, please post for help.

thx

manolo

[fario]

try to conect Vo to gound (contrast signal)

god luck

fario

[pay_c]

Just to go sure: You did not put in the MAX-IC to the LTC, right?

Is the correct display config chosen within MIOS upload (regarding the ID-header)?

Weird problem anyhow. When you change the contrast, do the black blocks react (getting lighter or darker)?

I would bet that it´s a cable problem. Really do check the cabling to the LCD again! Also for shorts (which sometimes are hardly seen). Get the datasheet @ Reichelt for your display and check the Pins of the LCD for correct connection. The 2x40 displays have two rows of 8 pins if I remember correctly. Perhaps the interconnection to the core is wrong due to that point (signals mixed up).

*goodluck!!!*

[manolo]

Hi,

we just found out one mistake. we're usin the jdm programmer and realized  the pcb-layout connect the 10k resistor between Vss and RB3 ( as needed for the PIC16F... ). So we changed the circuit that the resistor is now between Vss and RB5. But we don't have another new PIC18F452 to try ( bad luck ;-(  ). A funny thing is that the midibox64 seems to be functional, but only without the display. Hmm, we have to order some new parts and test it again.......

We'll hope the next post is a positiv one!!!!

greetings

manolo team

[moebius]

Hi.

So we changed the circuit that the resistor is now between Vss and RB5. But we don't have another new PIC18F452 to try ( bad luck ;-(  ). A funny thing is that the midibox64 seems to be functional, but only without the display.

That's not funny at all! ;D Actually, your PIC is working as it should, that resistor disables the low voltage programming mode (that automatically allocates PIC pin(s) for a programming interface, from the port connected to LCD). So, you've burned pic in LVP mode.

Try again, erase the pic and burn the bootstrap with the resistor in the right place.

Bye, Moebius

[manolo]

Okay, we burned the pic with the resistor in the right place and an additional power supply, with the same result as before. The midibox seems to work, but nothing is shown on the display. We also supply -5V to the contrast-poti. Now we can set the display to show four rows of black blocks instead of two as before. What went wrong?? Where is the mistake?

[manolo]

It works!!!!!!! We tried the MIOS-Studio instead of the Midi-OX and we have a full functional midibox64 now!!!! The Display is working.

Now we will work on the project and post some results in the future.

Thanx for helping. Maybe this topic can help other users.

Greetings

manolo