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Old 10th Jul 2020, 5:36 am   #1
Karen O
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Default Mini-scamp microcomputers

While there is such interest in switches and LEDs style of SC/MP microcomputers, I thought I'd show off these little gadgets I built about a decade ago.

They use an 18 pin PIC and have a simple, non-realtime SC/MP emulation. The 'memory' is the PIC's non-volatile memory and is pre-loaded with the Mk14 'Square root' program when the device is programmed. I used something like charlieplexing to drive all the LEDs. It executes slowly so that you can see the LEDs blinking. On completion of the program the 'HALT' LED comes on and the computer stops. You can then peek about the memory to see results, etc.

It's meant to be a kind of executive toy, I suppose.
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Old 11th Jul 2020, 6:45 am   #2
wireless_john
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Default Re: Mini-scamp microcomputers

Executive toy! Yes, I like that! I found a box of old ICs in my garage sometime ago, amongst them were some Z80s so I set about getting one to work.

I've been tinkering around with it for months and finally its working. It has no real use and when I was asked why I had made it I said for no other reason other than the pleasure and satisfaction I got from doing it!

I'm still working on it at odd times. I have a 1Hz oscillator under construction which will bolt to the four screws on the back panel so I'll be able to have an over-engineered clock! And the display isn't working yet. I wired the power to it the wrong way round first time and destroyed it so I'm waiting on another one from China.

To program it I'm using a simple IDE called zDev Studio and an assembler called Pasmo. As of today I've got it generating pseudo random numbers on the LEDs.

So now when I'm asked what it's for, my answer will be 'Executive Toy'!!

John
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Old 11th Jul 2020, 11:44 am   #3
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Default Re: Mini-scamp microcomputers

Hi Karen and John
Very nice microcomputers. It is easy to see that a lot of work has gone into them.
Any hobby is about doing something you enjoy. Most don't do anything useful.

John
Looking at the back of the display in your second photo. I am assuming that it is a HD44780 compatible type. If so and if it used in 4 bit mode D0 to D3 needs to be connected to 0V.
I know this only because I fell into that hole recently. I should have known better as I have used that type of display many times in the past.

Frank
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Old 11th Jul 2020, 12:24 pm   #4
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Default Re: Mini-scamp microcomputers

Thanks for that Frank. I did wonder about them floating so when the next one arrives, I'll connect them to 0V. It is 4 bit mode as you say. In the past, when using PICs where there aren't enough pins, I've used a shift register and then run it in 8 bit mode but clocking data out serially in to the shift register slows things down.
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Old 11th Jul 2020, 1:20 pm   #5
Karen O
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Default Re: Mini-scamp microcomputers

Projects like your Z80 computer are what it's all about, John.

For those who don't get it: TOUGH!
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Old 11th Jul 2020, 3:52 pm   #6
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Default Re: Mini-scamp microcomputers

I love making things that work and do something, the result is usually their end after a short while.

And people thought the "maker movement" was new!
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Old 12th Jul 2020, 10:19 am   #7
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Default Re: Mini-scamp microcomputers

I am the same Merlin... I love making "stuff" whether it is RF or other.. make it work.. then... "NEXT".. and the previous project........... may become a donor...I am on with my Tri band VHF transceiver.... which will be built into the case of my first major RF project .. the 40M SSB transceiver....I find it much more satisfying than shelling out for some "box" that many thousands of other amateurs have... and they have nothing to talk about. .
Sorry Karen "O" for hijacking your thread..
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Old 12th Jul 2020, 2:31 pm   #8
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Default Re: Mini-scamp microcomputers

Karen,

How do you do the lettering on the front panels of your designs?

John
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Old 12th Jul 2020, 9:20 pm   #9
Karen O
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Default Re: Mini-scamp microcomputers

Hi John,

My legends are simply images, prepared in any of a number of ways, printed off, and then laminated to prevent greasy finger marks. One of my mini-Scamps looks like a PCB, but it is really just an image reeled off on the computer.

Another forum member prints onto OHP transparencies to make clear legend sheets. The image is mirrored before printing so that the inked side is against the panel and therefore protected.

There are many opportunities afforded by an ordinary printer. I have even made a Nipkow disk using my printer!
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Old 13th Jul 2020, 6:42 am   #10
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Default Re: Mini-scamp microcomputers

Karen,

Ah, OK, thanks for that. Mine are done in a similar fashion.

I draw them with Microsoft Paint and then print them on thick paper/thin card. With Paint, it can be a bit of a challenge to make it print the right size!

Then I cover them with sticky backed plastic and glue them on to the appropriate panel with PVA glue. They are surprisingly hard wearing!

John
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Old 13th Jul 2020, 7:50 pm   #11
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Default Re: Mini-scamp microcomputers

Love them both

I really like the idea of a small cased unit as an executive toy for my desk in work... hmmm been wondering what to do with this stack of INS8050's that turned out to be MASK programmed Intel 8049 style chips not SC/MP and some overbuying on the Clear 'RED' LED's and Tag SPST switches for the SCRUMPI project...
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Old 13th Jul 2020, 11:45 pm   #12
Karen O
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Default Re: Mini-scamp microcomputers

I used DIP switches and (in the case of the 'mini computer' chassis version) bargraph LEDs. The result: something that fits in your hand. Programming is a pain though - I used an old stylus from a tablet. When I program the PIC the user EEPROM is pre-loaded with an SC/MP program so you can avoid all the tiny switch flipping!
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Old 14th Jul 2020, 3:36 am   #13
Karen O
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Default Re: Mini-scamp microcomputers

Here are the project files for those inclined to build a miniscamp
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