Cold Tea on a Sega Master System [BBC BASIC music demo]
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- Опубликовано: 9 сен 2024
- I've been adapting Richard Russell's BBC BASIC (Z80) to run on a Sega Master System to enter the /r/retrobattlestations BASIC month 6. It's been a very hot day and having a CRT TV running for the three hours it took to generate the output of this month's program hasn't helped matters, so I thought I'd cool down with some Cold Tea.
A PS/2 keyboard is connected to a passive adaptor in controller port 1 for text entry. A MAX232-based circuit turns controller port 2 into an RS-232 serial port, and programs are loaded or saved from a Z88 connected to that serial port running PC Link.
BBC BASIC (Z80) is Copyright © R. T. Russell
Cold Tea is devised by R.Cope from the original work by Andrew Robinson.
I was thinking of an internal circuit board, so that old bios and 8 kb ram came out.
and for that a 128kb eeprom, 128kb sram and as a controller ic atmega 32 with the sd card function as well as ps/2 for the keyboard.
something like that now costs less than 30 euros material.
Awesome!
Thank you, I've always had a soft spot for this tune. :)
Since I still have the two versions of these sega mega drives here, this atmega home computer project would also be interesting for this fairly old game console!
There, a modern Atmega chip could also play the bank switcher and read the sd card.
As also describe the Vram faster than the built-in CPU.
Since the Mega drive only has 64 kb sram as VRAM and the VDP chip works in a similar way to the master system.
Nice work!
Cheers, Kerm! :)
Because the Sega vpd chip can be stopped via nmi interrupt, so there is "time" per frame for the fast atmega to reload 16kb or more video ram, e.g. single images of a gif video from sd card, while the z80 cpu makes music to it
Was looking for the pinout of the serial adapter, but wasn't able to find a clear instruction in your blog article. The PS2 keyboard adapter is a nice one ...
The serial pinout is at the top of Serial.asm (pin numbers are given for DE-9 ports on the Master System, pin numbers at the other end will depend on what serial device you're connecting to). Pins are described from the context of a DTE (so TxD and RTS are outputs from the Master System, RxD and CTS are inputs to the Master System).
I should probably also mention that if you're going to connect the Master System to anything that uses RS-232 you'd also need an interface circuit to adapt the voltages (e.g. MAX232 chip or equivalent) - I don't think the Master System would be very happy to have -12V dumped onto its controller ports!
Nice! But how long did it take to position the TV for the video? 😄🤨
Haha, thank you! I had this set up so I could take a photo of it rendering the Mandelbaum set (this month's BASIC competition on RetroBattlestations) which took three hours to complete, so I had plenty of time to line everything up.
@@benryves Awesome job regardless. I wish I had time to learn to code. Always impressive how this seems to come so naturally to you.
great z80 project!
I also wanted to convert my 30-year-old master system into a real home computer with a ps2 keyboard and sd reader.
could a modern atmega 32 help here?
Thank you! That sounds like it should be possible, though in my case I wanted to keep the Master System stock so rely on accessories plugged into the controller port and a RAM expansion inside the cartridge (I use a Monopoly cartridge with 8KB inside). I did use an ATmega644P in an old Z80 project as an I/O controller, e.g. to read the keyboard, handle a serial port, and access an SD card over SPI protocol. It had direct access to the Z80 bus so could perform DMA operations. The "Z80 Computer - Mark 2" video on my channel shows that computer in operation and has some details about how it worked, though I never completely finished it or documented it unfortunately. All the best for your project! :)
@@benryves Thank you for your quick response.
I'm looking for a cheap homebrew mircocontroller solution to convert these old game consoles to the z80 learning system. Is there already a hobby project on github etc.???
I've had a collection of these ancient Sega game consoles over the years and it's a pity that you can only get expensive ROM game modules or something like everdrive for them or because everything costs too much money on the pc then use an emulator.
because for me the master system is not much different than a z80 msx computer, where the sega vdp chip can do 16 out of 64 colors, but cannot be converted to the z80 learning system.
Unfortunately, my z80 programming skills lie back more than 30 years and I don't feel like insane prices for real z80 vintage computers, e.g. cpc, msx, zx 48kb... to pay on ebay when I have something similar lying around here almost for nothing.
I don't know if the old games will still run, but we all know them by heart.
as a next idea or version of this board, throw out the old 16 kb sram memory of the vdp chip and replace it with a 512kb sram where the atmega then does the bankswiting and reads/writes the sram without the old cpu.
I want to have full control over the Z80 system here, like the action replay card did back then with the c64.
since the z80 can only address 64kb, the atmega could then manage the ROM via bank switching and at the same time work as a "frezzer" ala action replay carts including RAM save and loading function.
I have real difficulties:
Unfortunately, my personal knowledge of "Z80" CPUs" as well as the SEGA "VDP" Video CHIP in this SEGA SMS is quite limited.
Since I only programmed monotonous C64 6502 assembler when I was young... and the "VIC2" CHIP did a lot of work for the hard-working "programmer".
No, the Z80 or VDP was a completely different world!
Unfortunately, this "z80" system is very old and probably easier to program on a 6502 c64 "computer" that is almost as old.
In addition to the ancient Z80 CPU including assembler - without modern Flash RAM, SPI or USB..etc.
The ATMEGA also wants to be learned as an "MCU". Together with the Ps/2 keyboard LIB for this ATMEGA, e.g. 664 or 1284?
If young people or Z80 programmers (newbies like me...) just for fun want to have fun here,
there must an internal MCU circuit board with connections for a modern, cheap ps/2 keyboard and a mass data carrier via "sd card" reader should come here.
including a SYSTEM FREZZER with "functions" like something like an action replay 6 back then or the new Kungfu Flash ala C64
i think a sega mega drive would be a better retro learning system than a z80 master system, maybe with a simple gui interface including modern mini python as the programming language.
so the things just gather dust on the wall or in the closet and don't tune anything anymore.
Hi Benryves,
I am much interested in your Sega Master System Basic project. Have you made any progress developing a Basic cartridge with on board ram?
Many regards,
Alexander
Hi Alexander, thank you for your interest! It does support cartridges with battery-backed RAM (I use a modified Monopoly cartridge). Unfortunately due to a lack of general interest in the project I've not worked on it for a couple of years so can't really remember what sort of state it's in.
Might I download somewhere your modificated Basic version and the circuit diagram to connect the PS2 keyboard to the SMS?