I’ve read all the relevant documentation that I could find on LCD character displays—mostly this, this, this, and this, along with various sections of the MB SID documentation and dozens of forum posts—and I’m still left with a few questions…
First off, where I am in my project. Questions are down below. I have my MB-6582 power section fully built. I went ahead and built all four cores (I was going to do one at a time, but after you solder in all the resistors, capacitors under sockets, sockets themselves, and headers, there’s only like three more components per core to add). I checked all my voltages and everything checks out. I inserted my first PIC and successfully uploaded MIOS (though not the SID application yet). So everything seems good so far.
I haven’t ordered my 20x4 LCD yet (more on that later), but I have a 16x2 LCD handy (this one) and figured I would use that to test while I wait on more parts. The MB SID manual says that 16x2 is supported, just not recommended because of its size. I read the above documentation, get a cable all ready, connect it to the LCD, and…nothing. Fiddling with the contrast trimmer and the cabling, I manage to get a few weird things to display, but nothing that indicates things are hooked up properly.
Now, I strongly suspect that it’s either a mechanical issue with my connection (its hooked up somewhat haphazardly through a breadboard, rather than soldered) or a mix up with pin connections. But! before I go chasing phantom soldering issues, I am hoping to clear up a few questions I have, just to rule stuff out and gain a better understanding of how everything works.
HERE ARE MY QUESTIONS
First, does anything need to be changed in the code to support a given size of LCD? Like right now, I just have basic MIOS installed on my PIC, v1.9 as available as the top download link on this page; should I expect it to display startup information on any size (2x16 or 20x4, for instance) of standard LCD, or do I need to tell it what size to expect somehow? How about once I install the MB SID app?
Second, 4-bit mode and 8-bit mode. My understanding is that the MB SID app wants to run LCDs in 4-bit mode. Some documentation indicates that a special cable wiring setup is required for this (seen here), but while trawling the forums for information, a lot of folks suggest not to worry about special wiring. Not really sure what’s what here.
Third, can anyone offer a wee bit of guidance wrt choosing an LCD? I was looking at Crystalfontz and this LCD looks particularly striking. Green on black! Looking at the specs, I’m 99.9% confident that this part is compatible with the MB-6582. Only thing holding me back is the price: $25 once you add shipping. Meanwhile, there are 20x4 LCDs from China on eBay for like $6. I understand that you get what you pay for, but I’m wondering if anyone can comment on where that extra $20 goes on a Crystalfontz. Nicer colors? Less likely to break? Better contrast? More responsive? All of the above?
Last, my backlight trimmer doesn’t seem to affect anything. Backlight is on and at constant brightness no matter how this trimmer is set. I think I’m missing something obvious here.
Now, like I said, I understand that the simplest explanation is that I just don’t have things hooked up securely or properly. I just figured this would be a good chance to stop and ask some questions that were bothering me (and probably only still bother me because things didn’t work on the first try).
It’s one of the best pieces of documentation for the MB-6582 around (and I almost never found it because it’s hidden in some other forum!). I’m 90% sure I got the cable mapping right (using both your guide and my datasheet), but I’ll double check as I solder it.
Glad you got it straightened out!