[Coco] Electronics Newbie question

[Paulo Lindoso]

On top of this thread, what software (i use a mac) would you recommend to
design circuits and an eventual PCB layout?

Cheers
Paulo
Em 17/12/2011 01:11, "Andrew" <keeper63 at cox.net> escreveu:

> Robert,
>
> Depending on how long you've been "out of it", as far as everything goes,
> you may have a steepish learning curve (especially with proper interfacing
> with the CoCo's bus - from what I have seen, it is fairly straightforward,
> once you understand how address decoding and such is set up).
>
> The biggest problem you'll face is the fact that there isn't (afaik) any
> "solderable" PCBs that will just "plug into" the cartridge slot; you'll
> have to first either build one, or find a design for one (I think a few
> exist out there?), and modify it to suit your needs (then have it made, or
> make it yourself, etc).
>
> That can ultimately be a ton of work - just to get to a point of doing
> anything fairly basic...
>
> But there may be another option: Use the serial port(s)
>
> Either with a multi-pak interface and an RS232 cartridge, or via the
> bit-banger, you could probably set up a communications interface to a
> standalone Arduino board. What you would want to do:
>
> 1) Purchase an Arduino Uno (don't get fancy with a Mega, just go basic
> here)
>
> 2) Get the Arduino IDE set up on your computer/OS - make sure you can run
> the Blink sketch
>
> 3) Start learning how to program and work with the Arduino to read and
> write to the ports (blink LEDs, read switch states, etc) - the arduino.cc
> forums and the playground will help immensely; there is a TON of
> information out there on this
>
> 4) As you get comfortable with the Arduino, learn about how to build a
> "standalone" Arduino; that is, an Arduino built on a breadboard or PCB
> using minimal parts that can still be programmed by the PC, via a USB to
> TTL serial cable (you need simple parts like a pre-bootloaded ATMega328, a
> few capacitors, a 7805 regulator, a 16 MHz resonator, and a few other minor
> components)
>
> 5) At the same time, study the schematics of the original serial-port
> Arduino; learn how to interface using a MAX232 or equivalent
> (alternatively, there are methods using simple transistors as a
> buffer/voltage level changer that work well, too - a version of the
> Parallax Basic Stamp II used such a system - and I think there are a few
> standalone Arduinos that have been designed to use them, too)
>
> Note: I don't recall, exactly, but I think - IIRC - the bit-banger port on
> the CoCo is already TTL serial (maybe somebody else here can enlighten
> us?); if so, then the next step will be relatively easy...
>
> 6) At a certain point, you'll have the knowledge and feel comfortable to
> build and test that standalone Arduino, and connect it to a serial port on
> the CoCo. You'll have to learn how to program the Arduino to send and
> receive serial strings, to use as commands from the controlling computer
> (whether a PC or the CoCo)
>
> 7) All that's needed then is to write that software so you can send a
> string like "[P10=HIGH]" (set Pin 10 HIGH) or "[READ P12]" (read the value
> on Pin 12), etc - all via the serial port. The code on the CoCo should be
> fairly simple to implement...
>
> You can then do your interfacing via the Arduino, and have the CoCo
> command the Arduino to do simple things (or the Arduino can do more complex
> things, and execute those tasks based on commands from the CoCo, if you
> want).
>
> I'm looking back on all of that and now I am wondering if that is indeed
> simpler than going thru the cartridge port (grin); I personally think it
> would be, ultimately - the cartridge port is a finicky beast, from what I
> am lead to believe, and it is very easy to blow the 6809 in the CoCo (no
> buffering on the lines - it's a direct bus to the CPU). But, if you want to
> go that route, read everything you can and heed all advice on interfacing,
> so your CoCo will live a long(er) life!
>
> Good luck, hope this helps!
>
> -- Andrew L. Ayers, Glendale, Arizona
>
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