OSI Portable Project

[Sideburn]

Well the reference manual says to set it to a minimum of 500 and not to go beyond 640. I don’t know if that means the optimum pulse width would be right in the middle or not ?…

[ronin47]

Thats with the pot pretty much maxxed out. If I turn it all the way up then it gets just a tiny bit wider. So 500us is about as good as I can get.

Interesting, I can easily get up to near 600uS with mine.

And you are measuring the top of the waveform like I am?

If I max the POT out then i can get it goes to where the green arrow is (actually about half that far):

OH wait is that 600?

max.jpg

Looks like it might be 600...

[ronin47]

If you want to increase that pulse width beyond 500 microseconds, would it not make sense to increase R53 from 10k to 12 or 15k?

I'm thinking 12k would give a maximum pulse width of 550 us, and 15k would give 625 us, since the series resistance of R57+R53 would be increased by 10 or 25 percent.

Do you mean with R57 maxed out? Need to check what it is on my Klyball, but I definitely can get to 600us easily, a bit over IIRC.

[ronin47]

Well the reference manual says to set it to a minimum of 500 and not to go beyond 640. I don’t know if that means the optimum pulse width would be right in the middle or not ?…

That's what I was working on, but it may depend on your machine. I suppose starting low and working up would be the way to do it.

[royedmund]

I really want to 3D print one of these cases and the microcassette is a beautiful touch too... Also what is the bodge next to the character ROM? Extra video memory?

[Sideburn]

Yeah it has a 48 character mod and 2K video ram. Problem is I can't get any software or games to work right with those mods.

The story behind it is A friend gave me his superboard II.. It was his first computer as a kid and it was full of modifications and bodge wires all over the back of it. I didn't know where to begin and I had never even heard of the board. I am about 10 years behind him so by the time I got my first computer it was a trs-80 coco with color and sound and a case even!

It took me a while and a lot of help from the guys here to get it running and bxdanny on here had to make me a custom ROM to support the 48 columns.

There's a lot involved in the portable build. It took me a month off and on to design it. It takes over 100 hours of printing, the LCD display section is specifically designed for a particular LCD TV from the 90s and I had to strip the LCD PC board down as thin as possible. I made some incorrect measurements towards the end and the LCD didn't fit! in the end after shaving everything I could off the LCD board I still had to thin the back of the display lid down to 1MM. Just barely made it. and thickening up the display part would have been a MAJOR reworking of the entire thing. Then there was the building of the NIMH packs and power management circuit...

I plan on taking it to VCF Socal this year and I am brainstorming doing an Atari 8 bit "laptop" next...

** with some work, the display portion could be refactored to fit a different one as long is it can be whittled down to fit inside.

[Sideburn]

I found the perfect Microcassette tapes. The Maxell Ultra Dynamic's They are read and writing flawlessly. They must have been made for saving data!

s-l1600.jpg (267.55 KiB) Viewed 2451 times

[ronin47]

I found the perfect Microcassette tapes. The Maxell Ultra Dynamic's They are read and writing flawlessly. They must have been made for saving data!


s-l1600.jpg

Nice find!!!

Must get back to fixing my cassette in/out, but my 2012 MBP is currently taking up all the room on my workbench on account of having a dead keyboard.

Soon...

[Steve Gray]

Wow, really cool!

I'm interested in how the LCD is connected. Is it composite or is there a conversion such as composite to HDMI or RGB2HDMI? I've always been impressed by RGB2HDMI for its ability to configure the screen. On one project I did I was able to take a 640x200 resolution screen plus borders, that had a 640x128 active display area and exactly position it to fill an ultra-wide LCD panel perfectly. I think it would work great for your portable machine.

I have had the idea to put my 600D reproduction board in a cool case, and yours is very cool. Are you planning to release the 3D design files?

Steve

[Sideburn]

It’s composite. And it was difficult to find an lcd that would sync.
Ended up using a 90s lcd tv. I just found out about the rgb2hdmi and will be using that on an Atari 8 bit to laptop conversion.

** the design would need some modifications done to it and the display portion refactored to fit a different lcd panel and circuit. You can send me a PM if you deside to take the plunge and I can help you get it sorted.