MiSTer FPGA Forum

I've created a core for the Interact Home Computer and shared it on GitHub. You can find it at https://github.com/edanuff/Interact_MISTer. I tried to follow the discrete logic of the schematics as closely as possible in my Verilog code to make it as accurate as I could. I'm still working on it but it will load and run games from the cassette file format that existing emulators use. I still need to get joysticks to work correctly (right now I've mapped the USB keyboard arrow keys to the joystick) and I'm not sure how I'm going to get sound to work since I've yet to find a good HDL implementation of the SN76477 sound chip that it uses. This was my first major Verilog project, so I'm sure that a lot of it could be improved. Looking forward to comments!

Cool. Never heard of it, but then reading they only sold a few thousand, so I am not surprised.
I am sure the original designers would be pleased that it lives on. Well done.

SN76477 sound chip is mainly analogue which makes it difficult to do as a high level language, although if the machine only does single voice 4 octaves I
guess the Interact supplies an external VCO and just use the ADSR filter, so it may be possible to knock something up for it - have you got a schematic for it ?

Wonderful. Any chance to tweak the 15khz output? I get rolling image on my CRT TV.

Very nice, thanks.
Very primitive machine, especially considering it was released around the same time as the TI-99/4A - which was way ahead of it's time.
It sort of reminds me of the Mattel Aquarius, going by some of the videos I have watched.
It's machines like these that benefit from an FPGA core, it's then preserved for future generations.

MiSTer_Kirk wrote: ↑Wed Aug 11, 2021 9:24 pm Very nice, thanks.
Very primitive machine, especially considering it was released around the same time as the TI-99/4A - which was way ahead of it's time.
It sort of reminds me of the Mattel Aquarius, going by some of the videos I have watched.
It's machines like these that benefit from an FPGA core, it's then preserved for future generations.

The late 70's were a really interesting time for home computers with things moving very very fast in the span of a couple of years. The Interact must have been designed in 1977 and wasn't too far off from what other computers were shipping. They released it in '78 and shortly after went out of business and all the inventory went to liquidators who sold it out of the back of magazines like Popular Science. My family purchased one from those magazine ads. We owned it for a few months before getting an Apple ][ but it was my first exposure to programming and this project was a fun trip down memory lane. I agree with you about the TI - I've actually met one of the designer's of the 99/4A and that was definitely ahead of it's time and of course, the 9918A was incredibly important, but it's great to be able to revisit the history of that period.

macro wrote: ↑Wed Aug 11, 2021 8:20 pm SN76477 sound chip is mainly analogue which makes it difficult to do as a high level language, although if the machine only does single voice 4 octaves I
guess the Interact supplies an external VCO and just use the ADSR filter, so it may be possible to knock something up for it - have you got a schematic for it ?

Yes, you can see it attached. I did find a partial implementation of the SN76477 for the ABC80 here

edanuff wrote: ↑Wed Aug 11, 2021 9:59 pm The late 70's were a really interesting time for home computers with things moving very very fast in the span of a couple of years. The Interact must have been designed in 1977 and wasn't too far off from what other computers were shipping. They released it in '78 and shortly after went out of business and all the inventory went to liquidators who sold it out of the back of magazines like Popular Science. My family purchased one from those magazine ads. We owned it for a few months before getting an Apple ][ but it was my first exposure to programming and this project was a fun trip down memory lane. I agree with you about the TI - I've actually met one of the designer's of the 99/4A and that was definitely ahead of it's time and of course, the 9918A was incredibly important, but it's great to be able to revisit the history of that period.

Yes, there is definitely something rather fascinating about the late 70s, for computers, AND consoles - the Magnavox Odyssey, Fairchild Channel F, and of course the Atari 2600 - one of my favourite consoles of all time.
I didn't get my Apple IIe until it was mostly dead in the water, the mid 90s when retro hardware was lovely, and cheap.
The Ti99/4a, was definitely something else. The expansion possibilities, at that time, and now looked at from a modern eye, were amazing. The PEB, was something else, and huge. But also look at what people are doing today with the Ti, especially things like the F18a, Nano Peb, Finalgrom, etc..

I do like the look of the 'Interact Model One', that has a sort of 70s sci-fi vibes, something you might see as a prop in Dr Who. But I also get some Amstrad CPC vibes, crossed with a Commodore 116.

Thank you for this new core

edanuff wrote: ↑Thu Aug 12, 2021 12:10 am Yes, you can see it attached. I did find a partial implementation of the SN76477 for the ABC80 here

cheers, will add it to the list of things to look at

Thanks for making and sharing this, are you planning to add it to the official MiSTer repo?

Moondandy wrote: ↑Sun Aug 15, 2021 12:14 pm Thanks for making and sharing this, are you planning to add it to the official MiSTer repo?

I definitely would like to. I don’t know how to go about doing that.

I put a link to this thread in the Dev channel in the discord (well worth joining if you aren't already). I am not a dev, but a couple of questions: are you using the latest MiSTer framework and is the core free of all copyright material i.e. a baked in BIOS file that isn't public domain?

Moondandy wrote: ↑Sun Aug 15, 2021 7:08 pm I put a link to this thread in the Dev channel in the discord (well worth joining if you aren't already). I am not a dev, but a couple of questions: are you using the latest MiSTer framework and is the core free of all copyright material i.e. a baked in BIOS file that isn't public domain?

Thanks! Not using any copyrighted material. The memory initialization file for the rom area is a small 8080 assembly code program that I wrote that displays an error message if there's no boot.rom on the SD card. I'm throwing the .asm file for it into the repository just in case anyone wants to see it.

Thanks for your work on this core. I actually own one of these and it's great to see this rare and obscure machine preserved.

I was really surprised when I googled this machine, I wonder if it's where Alan Sugar got the idea for the cpc464 from with the built in tape deck..

What is the boot.rom? I have been searching without any success, I did not even find any reference to any kind of BIOS or System rom.
Any help would be appreciated.

You need a rom file. You can find these in most MAME collections or on the emulator sites listed in the README. It will typically be named Interact.rom. Rename it to boot.rom and put it in on the SD card.

jca wrote: ↑Mon Aug 16, 2021 5:54 pm What is the boot.rom? I have been searching without any success, I did not even find any reference to any kind of BIOS or System rom.
Any help would be appreciated.

took me a while to find it - as the saying goes google is your friend. (not sure it is your friend really lol)