Completed the V0.2 Mainboard
With a little trepidation, I did complete the V0.2 board.
It hasn't been the easiest part, oddly enough.
I definitely made a few serious upgrades on the board. And a few errors. Enjoy the video, and we can discuss after.
So I have a laundry list of things that I need to work on before I make a third board design. Not the least of which is getting the serial interface working. That will be part 2.
First thing I noticed... I need to adjust the Eagle Design Rules for more space around the pads for the VIAs.
My soldering skills are pretty abysmal. So I need to make sure the auto-router in Eagle doesn't place them so close to the soldering pads. I didn't have any problems this time through, but it wasn't comfortable. And since I can control that, I'm going to.
Speaking of the pads, I am going to take some time and adjust the libraries in Eagle for the 65xx chips and the EEPROM and RAM chips to use a larger pad and bigger holes. They worked for what I needed to do today, but I can't really install ZIF sockets easily in them.
The ZIF socket will also require me to turn the ROM/RAM 90 degrees if I keep the same footprint. And especially once I add the 6551 chip for serial interfacing and a header for that.
I forgot the main decoupling/filter cap (330uf near the USB Port), but that seems to be ok, since I'm now drawing power through the breadboard instead; so I can add one there.
The resistor package I picked in Eagle is too small, it's a 4mm package, but what I have are 5mm resistors, leaving me to have to install them at an angle. So I need to update those to a new package so they can lay flat.
C4 (part of the 555 Timer Circuit) needs to be polarized. But what I think I'll be doing instead is making a new 555 circuit that site with pins that would fill a typical full can oscillator, so I can add it for testing, but also use a 1/2MHz oscillator when I want. That will be a big part of the V3 board.
Finally, the holes for the mainboard for the LCD Mount are just every so slightly too small. I could use my tap and die kit to get the screws through, but I'll just drill them a hair bigger for now, and update the package for the LCD to use a larger hole in the next design.
If you're interested in a copy of either the V0.1 or 0.2 board, let me know, I can send you one of the extras.
Bu for the next video, I'll be figuring out how the W65C51 chip works and how I want to implement it. I've heard mixed responses on if it should be through a VIA, or direct on the data bus. I'm going to look at both.