GARTHWILSON wrote:
What's another VIA though.
Quote of the year!
Thank you Garth, that is amazing. Simply amazing. And, just to be 100% sure, I'm attaching my addition of the pull-up resistors for the columns. Are they correct? It's attached at the bottom I believe.
So you are correct about that LCD. Apparently the one I grabbed is not like others! Some have two column/controller selects, some have none at all, but ALL of them have an enable. Can I ask why it's important to not simply ground R/~W? I have seen many configurations where folks ignore the reading of the LCD because it's mostly insignificant. Assuming I will have the 2 separate selects AND an enable, could I just replace the R/~W line with Enable in this layout? Attaching the ~RST to the 6502 was a great idea!
This is what I was using as my basis of understanding the 2 select lines:
https://www.engineersgarage.com/128x64-graphical-lcd/Cool to have 2x SPI interfaces. Makes sense too! I'm definitely going to use something like this on one of them:
https://lastminuteengineers.com/arduino ... -tutorial/I actually already bought some of these, and will be testing on my Rapsberry Pi soon. An excellent tutorial I found is here:
http://elm-chan.org/docs/mmc/mmc_e.htmlI don't know exactly what I'd use an I2C interface for, but I have seen those around while I've been searching. If it fits, sounds like a good idea.
For the "Sync Serial" 6522 SR lines, I am lost as to what I'd use them for, as far as I am going. Again though, with the I2C, if it fits and doesn't use other chips, that's not a bad idea.
The beeper is a SUPER cool idea. And looks easy to implement. Thank you for that Garth.
Garth, I remember reading on your message on the introduction forum page how you were working on a big project for your job, and the boss kept asking for more features, and you kept putting them in. Feature creep. Though most of this seems completely possible and even easy, I'm still slow to toss too much on at once.
And Garth, a general theoretical question: For the SPI connections, why use PB1, PB5, and PB6? Could PB1, PB2, and PB3 have worked just as well? Similarly for many of the pins, why those specific ones, and not others? Again I'm new the VIA (and all of this), and I know PA and PB are different, but are pins WITHIN PB different from one another? And different enough that you decided on this configuration vs some other one? Just a theoretical question.
Now onto my general comments about my project:
1) It seems that 10cm x 10cm boards are MUCH cheaper than say 11cm x 11cm boards. So much so that I am thinking of trying to fit everything onto two 10x10 boards. Attached is a schematic I threw together last night in about an hour. Not all of the connections, resistors, capacitors, etc are complete, but this is a general idea. I'm using a '688 to find $7F00 for I/O which would be located on the second board (along with the 6522). Things will be TIGHT with just these, and I can't yet imagine how to fit 24 buttons on the next one along with the VIA and '138. The LCD will not be soldered onto any board, but will be connected with a ribbon cable to the second board.
2) I have been going back and forth a lot on what exactly I wanted this project to DO. So that you know, it's going to be on display at an event at the college sometime next spring, and as you know the best way to 'wow' students would be to put a video game on it. Pong or Tetris would be easy (and retro) enough. Because these boards are only 10x10 anyways, I'm considering making it "handheld". It would be look somewhat like a cross between a Game Boy and TI calculator, though bigger of course.
All that being said, I'm trying hard to keep chip count down. With that in mind, I have been back and forth on this cool IC I found on Jameco a while ago:
https://www.jameco.com/z/74C923-Major-B ... 44572.htmlThey have hundreds of these things, and like nobody else has them as far as I can see. Odd! Probably obsolete. But seeing how this is not much bigger than a 74HC138, could something like this simplify circuitry? Perhaps (dare I say it), it could even replace the VIA? Hear me out for a second: Seeing I'd have $7F00 through $7FFF free, I could use $7F00 (or $7FFE depending on high/low enables) and just run A0 into this chip? Similarly with the SDI and LCD enables and selects, just run address lines directly into these guys, through a '245, given that the '688 is telling me we are in I/O space. I'd be WASTING a lot of addresses, but the VIA is a huge chip for my small space. Thoughts?
As of now I'm going with the 6522 plan Garth has made, with little to no modifications.
Thank you Garth, and thank you all!