LCD problem

Testing/Troubleshooting
1

hi all, I’ve got another lcd problem. I’ve already made it throught hundreds of posts, but none seemed to help me.

I use two 40x2 LCD modules from reichelt, which were recommended on thorstens orderlist.

after I turn on the core module (mios1.7, setup_mbseq_v2.syx & main.syx successfully uploaded), the display lights up and shows:

  • 1 row of blocks for 2 seconds

  • then the blocks disappear (as if it wants to display the mios copyright note?)

  • blocks come back again (sometimes it shows 1 and a half row of blocks for a short time)

I tried the trimpots to adjust backlight and contrast, but the display stays blank (apart from the blocks).

I connected some buttons to the DIN module. the input monitor of MIDI-OX reacts to them, so I assume that mios and the application are running properly.

I also did the sysex send/receive test. It seems to work fine - I get prompt response, but strangely there’s a slight difference between the input string and the output string:

input string: F0 00 00 7E 40 00 0F F7

return sring: F0 00 00 7E 40 00 0F 00 F7

something wrong here??

the connections between core and display should be ok. I also tried another small 16x2 LCD module…same problem here.

I measured all the pins suggested in the midi debug article. all are fine, apart from this:

J2 Vd (GND) <-> PIC Pin 20  =  4.85 V

something wrong here??

I also tried to upload the midibox64 application (main.syx). after that, the display shows some strange hyroglyphs and the module sends a continuous sysex stream.

can someone help me out?

2

I measured all the pins suggested in the midi debug article. all are fine, apart from this:

J2 Vd (GND) <-> PIC Pin 20  =  4.85 V

something wrong here??

correction: this seemed to be an error of my voltmeter. I’ve got 5V here as well.

3

I also tried to upload the midibox64 application (main.syx). after that, the display shows some strange hyroglyphs and the module sends a continuous sysex stream.

The sysex stream is correct, because you don’t have an AIN hooked up so you get random messages.

It sounds like you have no problem loading MIOS and apps, which means the problem is most likely the display wiring is messed up.

I tried the trimpots to adjust backlight and contrast, but the display stays blank (apart from the blocks).

So do they have the proper effect: the backlight should get lighter and darker, and the contrast should make the blocks lighter and darker.

Double(triple) check your lcd connection, cause I think that is where the problem is.

Good Luck…

Justin

4

uuuuhhh oohhh uhhhh…all blame goes to me! I found out that the 6th bridge at the bottom side of the core has been connected to a wrong pin. how embarrassing.

displays are working fine now. yeehaw!

thanks for your time…