Starting a new 6502 design...VGA starting to come together!

[cbmeeks]

Hello everyone! It's been a long while since I've been active in the hardware scene. I just wanted to say I'm around and excited about a new 6502 design.

This one is going to be heavily based on the Pico. I have a pretty good start on the VGA piece of it. I know it's bad practice, but I started the video before the 6502 part. lol But hey...the Apple II is a video system with a CPU attached right??

For those interested, I decided to go ahead and open source the video section which is just some tweaks from the Hunter Adams project. Mine uses 320x240 resolution with 6 bit color (63 colors plus black).

Each 8x8 text cell uses the PETSCII font (sorry, ASCII users...) and can have it's own foreground and background color.
I'm going to put things like sprites on pause for a bit while I focus on some CPU/serial integration.

Anyways...great to be back! Oh, I will be out of the country later this week for our 20th anniversary. But when I get back, more progress to make!

https://github.com/cbmeeks/VgaPico

[Rumbledethumps]

Coincidentally, yesterday, someone posted a port of Hunter Adams graphics code to the Picocomputer 6502.
https://github.com/orgs/picocomputer/discussions/53

How is your design going to differ from the Neo6502 and Picocomputer 6502 projects? You commented on a couple of my videos so I know you've seen the Picocomputer design. The Neo6502 is from Olimex.

[Yuri]

I was considering using my Teensy 4.1 to generate VGA graphics for my 6502. Makes me think that perhaps my idea is more viable than I initially thought. ^^

[cbmeeks]

Rumbledethumps wrote:

How is your design going to differ from the Neo6502 and Picocomputer 6502 projects? You commented on a couple of my videos so I know you've seen the Picocomputer design. The Neo6502 is from Olimex.

I'm not familiar with the Neo6502. I actually don't know a lot about your Picocomputer...at least not the internals. One similarity would be using more than one Pico. In fact, I might be using three. Which seems crazy but I'm not sure yet. I have an idea I want to try on using a Pico as glue logic among other things.

Before I settle on too much, I have a few graphical issues I have to resolve. I'm not looking for 500 sprites on screen but I'm finding that a 320x240 resolution is actually quite high when you use 16x16 sprites. They look way too small. Anyway, after I lock down the graphical features, I will know more.

Some thing I know I will not do is 15-bit graphics like you tend to see on Pico VGA designs. I just don't think it fits a 6502 computer but that's just me.

[cbmeeks]

Yuri wrote:

I was considering using my Teensy 4.1 to generate VGA graphics for my 6502. Makes me think that perhaps my idea is more viable than I initially thought. ^^

I have a few Teensy's but I regret I never did much with them. I was into the Propeller for a long time and even bought the P2 dev board. I have to admit, however, that the $4 for the Pico keeps pulling me there.

I would love to see some Teensy examples with the 6502. It seems to have more than enough capabilities. Are there many VGA designs with it?

[Rumbledethumps]

cbmeeks wrote:

...using more than one Pico.

Neo6502 = 1 RP2040
RP6502 = 2 RP2040s
CB6502 = 3 RP2040s
Do I hear 4? Going once... going twice... SOLD!

[cbmeeks]

Rumbledethumps wrote:

cbmeeks wrote:

...using more than one Pico.

Neo6502 = 1 RP2040
RP6502 = 2 RP2040s
CB6502 = 3 RP2040s
Do I hear 4? Going once... going twice... SOLD!

Looking forward to seeing your 4 Pico 6502.

[cbmeeks]

Slight update...

The VGA driver I have is working pretty well. I can support resolutions from 320x240 all the way down to 40x30 pixels!

Yes, super lowres for those like me who enjoy Apple II type art.

Supported resolutions are 640, 320, 160, 80, 40 in horizontal and 240, 120, 60, 30 in vertical pixels. Any combination works. All with 64 colors.

I also need to finish my PETSCII <-> ASCII conversion routines.

Anyway, I am going out of the country tomorrow but I will try and post the final update before I go if anyone is interested. I hope to use this driver on my (yet unnamed) 6502.

[Yuri]

cbmeeks wrote:

Yuri wrote:

I was considering using my Teensy 4.1 to generate VGA graphics for my 6502. Makes me think that perhaps my idea is more viable than I initially thought. ^^

I have a few Teensy's but I regret I never did much with them. I was into the Propeller for a long time and even bought the P2 dev board. I have to admit, however, that the $4 for the Pico keeps pulling me there.

I would love to see some Teensy examples with the 6502. It seems to have more than enough capabilities. Are there many VGA designs with it?

I've seen one or two.

The 4.1 would need an external DAC of some sort to drive a proper VGA signal; but at 600MHz I think one could pull off some interesting 16/8-bit era graphics with it. I'll see if I can at least get a sync pulse out of it and wire up some latches for the RGB. My collection of parts are all 5V so I'll have to get some 3.3V parts to work with it.

As for interfacing with the 6502, seems like it should be pretty easy. The 4.1 has more than ample pins for R/W, chip select, and 8-bits of data to/from. I should have some 5V to 3.3V buffers that I can use to talk to it.