All the possible reasons for LCD showing only blocks/bars

Testing/Troubleshooting
1

Hi fellow midiboxers!

I have followed this guide from the UcApps website to build an lcd cable: http://www.midibox.org/users/jim_henry/building_a_midibox_lcd_cable.pdf . I have attached the datasheet of my LCD and the pin numbers exactly match those in the guide (if I’m correct).

I’ve soldered all the cables to the correct pins and I only got the blocks on screen. So then I’ve resoldered everything again after checking for broken cables with a multimeter and made sure there were no shorts after soldering.

  • I’ve uploaded Mios 1.9G with MiosStudio and after that the Midibox 64 app, MiosStudio says Mios8 is running fine. The core began outputting loads of midi messages as expected since the Ain pins weren’t grounded, after temporarily connecting 8 potmeters they worked as expected.

  • I’ve tried the LCD on 2 different core8 modules (both with a different Pic) and both show only blocks

  • The backlight lights up as expected, the contrast and brightness potmeters work as expected

Could the only reason be that datapins d0-7 are incorrectly connected? Or are there more possible causes for this behaviour?

Thanks in advance!

[LCD1602C.pdf](< base_url >/applications/core/interface/file/attachment.php?id=9239)

2

One thing to consider: PIC18F4685 only outputs in 4-bit mode, and some (most?) LCDs won’t work in 4-bit if you’ve connected up all 8 data lines.

So check if you are using PIC18F4685 and use this wiring instead.

http://www.ucapps.de/mbhp/mbhp_lcd_4bit_mios8.pdf

You are correct though, if the data lines are not correct, the LCD won’t receive the correct commands to initialize or display characters.

3

can also be a dead lcd…i remember once feeding the wrong pwr-pins with my psu, resulting in a dead pic and a dead lcd, showing only blocks…maybe you´ll need another one to test…

4

@Tim B: where are you? I have dozens of spare LCDs of various sizes that I can give away for free… it just depends on what you want to spend on postage.

5

Thanks for the replies guys!

Sorry I forgot to mention in the original post that it’s a Pic 18F452, so I guess for that one I need all the 8 datalines right?

@Wilba: Wow, thanks for your generous offer! I live in the Netherlands. I see on the Australian post website that the cheapest way for sending regular post or a package is between $12-20,- which isn’t too bad! I’ll PM you right now!

6

Sorry… wrong advice I was going to give.