RC2014 Graphics Adapter missing?

[Olaf Dannath]

Welcome to the Community! 

Some weeks ago I bought my RC2014 Kit. 

The only thing I miss is a proper graphics card. So far everyone has probably been satisfied with the serial terminal output. But for me the “Home Computer” is only complete with a real graphics Adapter.

Is someone here the same opinion or maybe work on a board or is there a reason, I do not know why, there is so far no graphics card for the RC2014?

For me, I want to build a graphics Adapter for my RC2014. But I don’t know if my skills are high enough to do all the things that are necessary. Especially the Firmware and programming stuff.

I hope,that perhaps is someone here, who would like to participate in such a project, or can help me.

Greets

Olaf

[Scott Lawrence]

I was looking at the Colecovision/Adam video circuitry just yesterday.  It's Z80 based, and uses port IO to access the video system.  I'm really tempted to get a colecovision, and hack a cable to a RC2014 bus connector. ;)

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Scott Lawrence
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[PianoMatt]

I see a few possibilities for adding graphics to the RC2014. There's the TMS9918, used in the Coleco and MSX computers. There's also the Mototola 6845 that was used for CGA graphics, as well as being used in the Amstrad CPC and BBC Micro computers.

[Peter Willard]

I managed to purchase a 6845 on ebay... these are still readily available, I guess.

[Spencer Owen]

The hardware side of things is not particularly complicated - but the software to drive it is way out of my league!

As far as I see it, there are essentially two different routes that a graphics card could go - replicate the circuitry from an 80's computer, such as Colecovision, Amstrad, etc as mentioned above.  Or start afresh with more powerful components for a better display.  Going down the replicated circuit route has the advantage that the software is easier because you can pretty much reuse the original ROM from Colecovision, Amstrad or whatever.  However, IMHO, if you start to use the graphics and ROM from an Amstrad CPC (for example), why not just buy an Amstrad CPC to start with?  It would be cheaper and easier.

Designing a modern circuit it's a trivial task in itself.  But getting a software routine written, particularly to support both MS BASIC, and CP/M would be an epic undertaking.  Although I'm happy to be proven wrong! :-)

Cheers

Spencer

On 15 June 2017 at 18:06, PianoMatt <mattyb...@gmail.com> wrote:

I see a few possibilities for adding graphics to the RC2014. There's the TMS9918, used in the Coleco and MSX computers. There's also the Mototola 6845 that was used for CGA graphics, as well as being used in the Amstrad CPC and BBC Micro computers.

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[Peter Willard]

I keep thinking that a Parallax Propeller would make a good vga "function block" that would save space and parts.   If it weren't for the 3.3V requirement, I'd have thought about it more.

[Scott Lawrence]

I'd be glad to prove you wrong. ;)

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[Spencer Owen]

On 15 June 2017 at 18:30, Scott Lawrence <yor...@gmail.com> wrote:

I'd be glad to prove you wrong. ;)

Excellent!  I always learn something when I'm proven wrong :D

Spencer 

[Spencer Owen]

On 15 June 2017 at 18:30, Scott Lawrence <yor...@gmail.com> wrote:

I'd be glad to prove you wrong. ;)

[Scott Lawrence]

Sidenote: I've been starting to wire up an adapter from a Pac-man boardset to the RC2014, so that I can display stuff and move sprites from the RC. ;)   I could expand it such that it's a textual interface as well...  Granted, it uses a chunk of RAM for the video memory. A port-interface version would probably work much easier. ;)

-s

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[Peter Willard]

I thought a lot of the graphic output solutions had dedicated RAM.

[Scott Lawrence]

For what it's worth, Pac-Man (and many arcade systems of that era) used shared memory.  In Pac-Man hardware, there's a chip that does bus managing so that the video hardware can access the same ram as the CPU, just one at a time. 

Actually, Pac-Man hardware (same as Pengo, Ms Pacman, Nibbler, Rush'N Attack/Green Beret, Galaxian, and a bunch of hardware ) doesn't use port io for the video access at all... it's all a blob of RAM.

For Pac anyway, 0x4000-0x43ff is the video character ram for a tiled background.  Each tile is an 8x8 pixel, 4 color image, and is stored in a character ROM.  0x4400-0x47FF selects the colors for these tiles.  (each color is a selection from a palette defined with resistors on the mainboard and a prom)  The character ROM is not accessible from the CPU.  You can just say "put character 0x42 here" and then "make it color 0x03"

There's another chunk of memory that you use to pick a 16x16 4 color sprite to draw on the screen, its x,y coordinate, its color, etc.  There are 6 such slots on pac-man... 8 or 12 of these slots on Pengo, and something like 32 of these slots for Rush'N Attack.

More info about the hardware here:

https://github.com/BleuLlama/GameDocs/tree/master/guide/pacman

pac-man memory map here:

https://github.com/BleuLlama/GameDocs/blob/master/guide/pacman/pacman.mmap.txt

On Thu, Jun 15, 2017 at 1:57 PM, Peter Willard <petew...@gmail.com> wrote:

I thought a lot of the graphic output solutions had dedicated RAM.

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[Eric Matecki]

@peter

This Propeller board should be easy to adapt to the RC2014 :

http://www.malinov.com/Home/sergeys-projects/parportprop

Open Source Hardware & Software.

[Tor-Eirik Bakke Lunde]

I started work on one earlier, but haven't received the PCBs yet so do not know if it ends up working properly. I'm documenting it as part of the 6502-based machine I was building, but included the option to take input from the TX/RX pins so should work the same on the RC2014. Schematics at https://github.com/tebl/RC6502/tree/master/RC6502%20Video%20Adapter using ATMEGA328p as chip since it is 5V based, the Parallax I never got started on since there doesn't seem to be much focus on it that I've seen outside of the US.

I did want to implement a purely analog solution as well, that's what the general video connector is all about. Haven't completed any of the work on making a PCB out of it, but I'm working off of the guide at http://www.waveguide.se/?article=bitmapped-video-interface to do this. That way I get to make one cheating microcontroller-based solution and one that implements it the old way.

[Eric Matecki]

Ah the old way... ever heard about the Vulcan-74 VGA graphics adaptor for a 6502 computer ?

Here are some videos : https://www.youtube.com/results?search_query=vulcan-74+vga

And the main thread at 6502.org (loooong...) : http://forum.6502.org/viewtopic.php?f=4&t=3329

That guy is crazy ! But I like it :)

[Tor-Eirik Bakke Lunde]

I've seen it though there are things to be said for simplicity when attempting to learn how things work. Put together a ZX Spectrum Harlequin kit a couple of weeks ago, and while it was fun to have done it there are simply too many components to it in order to figure out how each of them work - stuff just seems like magic at that point, and when it doesn't work I end up just stabbing it with a soldering iron hoping to fix whatever it was. The MC3 solution is still just black and white with an awful resolution, but you can follow along with it and after staring at it long enough you understand how it ticks.

I appreciate the builds, but they end up in the see-what-I-can-do category and always seem to lack the directions on how to do it yourself. I started my own Apple 1 Replica build after watching Ben Heck do it, but only after ordering a shitload of chips did I realize that he almost never includes the technical information on the builds - what you get is just the window dressing though I understand that's why 99% watch them for.

[Elia Mady]

I was wondering, is Chapter 9 of "Build your Own Z80 Computer" by Steve Ciarcia's a starting point for something suitable?

Elia

[Jan S]

I'm also attracted to the idea of some kind "graphics card" as an alternative to the serial terminal.
However, I lean towards using a chunk of the existing ram as "video ram". The Nascom works that way, and from a program point of view it's simple to handle. And - I might add - it's fast.

A few notes about the Nascom memory map:

0000H - 07FFH  2K Monitor (NASSYS)
0800H - 0BFFH  1k Video RAM (not all visible on-screen)
0C00H - 0FFFH  1K Monitor Workspace
1000H - FFFFH 60K Multi purpose RAM

The MS-Basic could be switched in (linkblok):
E000H - FFFFH  8K Microsoft Basic (4.7)

Writing a byte - let's say 41H (ASCII letter "A") - in address 080AH, makes an "A" immidately appear in the upper left corner of the screen.
The video RAM is constantly scanned through clever use of counters and multiplexers, and it's contents are used to address one or two 2716 Eproms that holds the graphic layout of the character set.
The data lines of the character eproms are shifted out serially to create the datastream a video signal is build of. The result is that a beautifull "A" is formed on the screen - complete without involving the CPU :-)

Now, there are several ways to proceed down this path. Copying the Nascom idea, IC for IC, would result in an unattractive chip count.
Here's where e.g. the propeller or the like could come in quite handy, as it could cover the video building part of the job at hand.

I've dropped the idea for now using dual port RAM. The thought was tempting though

Just some thoughts ........

/Jan

[Scott Lawrence]

I was considering using dual-port ram as a sort of USB-enabled EPROM emulator at one point... and yeah.. it gets really pricey, really fast.

-s

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Scott Lawrence
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[Peter Willard]

Its too bad that the CRT9128 chip  is pure unobtanium now.

[Olaf Dannath]

I looked what parts I have in Stock. And found a CPLD and a FPGA Board for 5 Volts, that I bought some years ago for a never realized Project.

Then I brainstormed a little bit and on my sketch you can see the first result. 

The costs of the parts do not matter. 

I want a board with full programmable flexibility. And I want to learn to program the CPLD and FPGA.This will be the first time I use some of this parts.

For the CP/M I need a banked RAM/ROM Board too, so I implemented this. With the CPLD I can program every Adresslogic, and Memory Map I want.

 And If I want to use this Board with a serial Input for a microcontroller for example then I programm a serial Input in the CPLD. 

The FPGA generates all of the VGA timing Stuff and Read of the Video Memory, and attributes etc.and put this together to output it to the DAC. 

At first I will beginn with a "simple" Textmode with some Color Attributes.The character Generator Rom I will store in the RAM/ROM of the FPGA.

 The next step could be some bitmapped Graphic Modes. 

But this Design can also be extended by routines for sprites, or other draw routines. with special registers. 

And over the 3 lines from the FPGA to the CPLD could be Interrupts commited or the EEPROM rewritten or somethin like that..

I know, the purist says, why you dont program the RC2014 completely in the FPGA. But that is not my intention. And I Have most of the parts here. the Engineers in the 70tes and 80tes used often some Parts like the ULA or other Videoprocessors. I want to use the FPGA instead because I have no private chip-fab to produce a processor for me. I see for 5000 bucks I can buy some softcore vhdl code from old videoprocessors. But I dont have the money and I want to learn how the things be programmed and work together. And by this design I could try out different solutions by programming without any Hardware changes.  

What do you think about the design?    

Thank you and greets

Olaf

[Spencer Owen]

On 16 June 2017 at 23:34, Olaf Dannath <olaf.d...@dannath-edv.de> wrote:

I want a board with full programmable flexibility. And I want to learn to program the CPLD and FPGA.This will be the first time I use some of this parts.

Sooner or later I know I will have to get my head around FPGA programming.  I dipped my toe in the water a year ago and got an appreciation of just how flexible and powerful FPGAs are... and also how much I still had to learn!

It's great that you've got an FPGA playing with the RC2014 :-)  If it can run as a graphics adapter too, then that's awesome :D

Spencer 

[Scott Lawrence]

has anyone here attempted to make a RC2014-BUS to 8-bit ISA adapter?  With something like that, you could use MGA/CGA/EGA/etc cards directly..

and for that matter, many of the 8-bit PC sound cards... Ad-Lib, Sound Blaster 1, LAPC-I, etc.

-s

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[Spencer Owen]

Not that I know of.

However, Dr Scott Baker has now started porting his RC2014 boards to ISA :-)

https://youtu.be/UOVpdZYiT-c

Spencer

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[Olaf Dannath]

https://ciernioo.wordpress.com/tag/z80/

Probably could this be modificated to the RC2014

[Jay Cotton]

Thats awesome.  I just don't have the time for it right now. 

[Sir Isaac]

I'm researching graphics card options for the RC2014 myself. Not sure if this would work or not but, interesting.

https://www.tindie.com/products/Nuclear_Man_D/ngt20-arduino-vgantsc-video-shield/

Might be a possible solution until something else is developed.

[Søren Amtorp]

I'll give a damn about the purist. I like the FPGA approach. My immediate thoughts  is - clone the Amstrad design and implement it using a fpga it must be doable somehow. Beside that the FPGA give you a lot of possibilities. Ok it is not pure retro - but fun....

[Sir Isaac]

"Pure Retro" for the graphics may not work too well for everyone's setup either. 

I guess it would be nice to use an old crt for it but really, I'll take a flat screen using hdmi any day lol

an fpga may also open the door for scaling options to scale the graphics up to fit an HD screen better too.

[Peter Willard]

No kidding... finding a Monitor that accepts Composite Video is a chore now. 

[PianoMatt]

I'm covered :)

[Ed Thierbach]

I'm covered :)

Commodore monitors were awesome. A local thrift shop had one just waiting to be had (by me), but the guy at the electronics counter refused to sell it; he was keeping it for the store's use. He said. :-)

I've never designed hardware; how much harder is it to design a board with modern output, than one with composite or RGB?

-Ed- 

[PianoMatt]

The lazy way is to just use a cheap Video DAC that takes composite/RGB and converts it to HDMI

[Simon Swain]

Would love to see some trs80/video genie style graphics. 1k of video ram with an ascii char at each location, and block graphics in the top range of the charset.

A character generator chip does most of the work. CPU doesn't have to do much. Maybe some way the Pi zero can help get it to hdmi. Schematics are available online in the system-80 (aussie version of the video genie) technical manual.

Plenty enough for some good games.

[Scott Lawrence]

Would that be 1k of video ram that fits within the 64k of the CPU, or is it addressable through port writes? 

I've been thinking about all sorts of ideas to do a video card with framebuffer, from an ISA interface adapter (for sound cards and video cards, transposing signals, and tunneling ports to the card), a shared RAM card... but where do you put it for maximum compatibility?  Probably just below DC00h so that you get max ram for CP/M... or do you make it movable?  Put it up at FF00h but switch down to DC00 for CP/M use?  or perhaps the entire thing sits on a port or two.  One port for flags (serial mode, graphics mode) the other for data writes...  have it be 68B50 compatible... so you can read and write to it... read from a keyboard device, write to the frame buffer... but then, why not just have it be a serial device itself, and send escape codes to switch into graphics mode and put the heavy lifting on the terminal... it could be VT240/ReGIS terminal emulation, perhaps with additions to set graphics sprites etc....   and I'm back where I started, working on LlamaTerminal...

So in my mind, these are some possibilities:

- ISA Interface/Interposer for Sound, Midi, CGA/EGA/VGA/Hercules video

- Memory-mapped (shared memory) video buffer below DC00 or at FF00 or switchable for compatibility

- Custom port interface (data + control) - writes to data are either graphics commands or serial console data (text wrap, vt100 commands handled by the data catching code, characters written to the framebuffer in appropriate places

- Serial based Video Output Unit.  (could also be marketed separately)... either software (LlamaTerminal) or hardware (Grant Searle's) but with extensions (VT240/ReGIS) to handle graphics rendering and sprites

-s

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[Jan S]

I'm going for a minimal (user-selectable) slice of common memory. I ordered a pair (one in spare when I "screw up") of dual-port static ram's, which I hope will do the trick. Being very aware that the main obstackle are my strongly reduced skils. But what the heck!, I'm giving it a go anyway.... ;-)
Princip:  ASCII in => ASCII out, and block graphics while I'm at it :-)
So, "poke" 65H in location xxxx and see an "A" popping up on the screen somewhere :-)

I didn't know that TRS80 did the same as Nascom, but that can't be a bad thing :-)

I really think we (or I at least) need a simple "videocard"

/Jan

[phillip.stevens]

So in my mind, these are some possibilities:

- ISA Interface/Interposer for Sound, Midi, CGA/EGA/VGA/Hercules video

- Memory-mapped (shared memory) video buffer below DC00 or at FF00 or switchable for compatibility

- Custom port interface (data + control) - writes to data are either graphics commands or serial console data (text wrap, vt100 commands handled by the data catching code, characters written to the framebuffer in appropriate places

- Serial based Video Output Unit.  (could also be marketed separately)... either software (LlamaTerminal) or hardware (Grant Searle's) but with extensions (VT240/ReGIS) to handle graphics rendering and sprites.

There's another option, that is useful for video, as well as a bunch of other stuff, and that is to build an I2C interface card for the RC2014.

It might not be retro, but I2C does tick a lot of boxes for connectivity for a whole range of sensors, actuators, and video interfaces, while minimising the need to have "Yet Another Board" in the SKU list, and an even bigger back plane board.

I chose to work with the PCA9665, because it is the last device to support 5V signal tolerance (even though it is powered by 3V3). I've written some drivers for PCA9665 (note untested, and probably quite broken still), but I should have them working within the next few months. They might be useful as a start, as I hope they'll end up in the z88dk sooner or later.

Anyway, my 2c or 2p, based on experience with video on 8-bit AVR devices.

Phillip

[Scott Lawrence]

I2C interface for it sounds awesome.  That opens up a huge array of expansion devices too! 

count me interested!

-s

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[Olaf Dannath]

Yes, I2C would be a nice Extension of the RC2014.

I googled this Chip :

http://www.waveguide.se/?article=42&file=PCF8584.pdf

What are you think, about it?

Greets

Olaf

[Jay Cotton]

PCF8584 in a DIP package is not available anymore.  You can find it on ebay but

I don't trust that source.

I think MCP23017 might be the better part.  It's  available in DIP/SM packages, is still

current shipping part.  And best of all $1.29 at mouser.com.

jc

[phillip.stevens]

That's a good find, for both SPI and I2C. When following up previously, I only looked at NXP options. And they are expensive. The Microchip options look good and cheap.

Still the PCA9665 has very deep buffers to its advantage, which make it easier to service, but still bus state changes need to be handled by interrupt.

Managing the IM2 interrupt chaining on Z80 would be challenging. Not my skill level, I'm afraid.

[Thomas Riesen]

Hi all

Maybe this is an idea: https://www.youtube.com/watch?v=bxYLQAJTAtw

Regards

Thomas

Am Donnerstag, 15. Juni 2017 18:17:50 UTC+2 schrieb Olaf Dannath:

[Thomas Riesen]

...

and the link to the modul: http://www.4dsystems.com.au/product/uVGA_III/

[Simon Swain]

Would that be 1k of video ram that fits within the 64k of the CPU, or is it addressable through port writes? 

The TRS80 (and system80/video genie/lnw80) had is as part of regular RAM. You could peek and poke it or use LDIR etc to blit regions.

But the charset from 128-198 was a set of 2x3 graphics cells, so each byte of screen ram held an ascii character or some pixels. The character generator did most of the work. To draw individual pixels you'd have to do some bit twiddling on the character in that cell.

http://www.trs-80.com/wordpress/zaps-patches-pokes-tips/graphics/

This page has manuals that walk through how the video system works

http://www.classic-computers.org.nz/system-80/manuals.htm

Simon