A1200 hardware hacking

[xeron]

I'm putting an A1200 motherboard inside the case from a Technics Hi-Fi CD-Player, to make an AGA CDTV-like computer.

The front of the CD player has loads of buttons, and i'm wondering what the best way to attach them to the A1200 is, so that I can write software to make them do what they say (like the Eject button to eject CD Rom, play button to active OS3.9 CD player etc. etc.). Also, I intend to put a VFD (vacuum flourescent display) on the front of the case, in place of the custom one that is already there.

So, I need a bunch of inputs (switches), and 3 outputs (VFD clock, reset, data). My initial thought is to use the parallel port, since it has 8 independant I/O pins, but I'm wondering if it would be possible to hook this stuff up without losing a standard port.

I have access to a PIC programmer through my work, but ideally i'd like to be able to hook all this up with just a few passive components and a little bit of soldering.

Any ideas?

[amigamad]

Im not sure how you could connect and use the buttons but eyetech used to sell a key board controler that also had infra red and you could program it to do difrent things as long as you had a remote controll  that was compatable. :-?

[xeron]

Hmmm... an IR transceiver doesn't help me at all really. Even if it did, I think it connects to the parallel port, which I can just wire the buttons to anyway!

I'd rather save all the standard ports, if possible. I was wondering if the clock port would be easy to use...

[Brian]

I'm pritty sure the clockport is a standard port on the A1200 and I think you might want to save that for a sleek internal soundcard perhaps? If you know how to progrma and stuff you could use the other half of the clockport (that usually don't have any pins) and whire the thing up to that?

I don't have any progging experience on the Amiga though, so I couldn't tell if it would be an easy way. But it should be as easy as hooking the thing up to the other half of the clockport that's often used for other hardware.

[xeron]

I don't plan on super-expanding this A1200 (it'll never replace my souped up 4000, or my AmigaONE), I only intend to add an 060 accelerator in the future, so using the clockport isn't a problem.

In fact, Ian Stedman had a design to hook up an Intel 8255 chip to give 24 digital I/O pins from the clock port, but he has since changed it to use the parallel port :-(

I have no experience of designing this sort of circuit, but I have no trouble following simple diagrams and converting them to veroboard. Its a shame Ian didn't keep the old schematic on his site...

[Stedy]

in fact, Ian Stedman had a design to hook up an Intel 8255 chip to give 24 digital I/O pins from the clock port, but he has since changed it to use the parallel port

The design is done and I have a basic autorouted PCB but I have not built that version. For the parallel port version, I have the PCB next to me, got to get soldering.

If you want the schematic, I will upload it this weekend with the next updates.

To interface the 8255 to drive LEDs you would need a buffer chip like a 74245, as it has a crap source/sink capability.

[xeron]

I take it a VFD would likely need a 74245 as well?

Wiring up a bunch of switches should be pretty easy though?

[Stedy]

I take it a VFD would likely need a 74245 as well?

I do not know how you drive a Vacuum display. What voltage/current does it need?
A 74245 (8 bit bus transceiver) is a good idea for any outputs in case you screw up, you blow a cheap chip oh and has +/-32mA current capability per output.

Wiring up a bunch of switches should be pretty easy though?

Yes. You may need debounce circuitry though. You can use software or hardware to debounce a switch.

Take a look here for suitable circuits:
http://www.ianstedman.co.uk/Amiga/i_f_circuits/i_f_circuits.html

Ian

[xeron]

I'm actually a programmer for a company that builds fruit machines, so writing things like a software debounce routine is second nature to me ;-) plus it saves a couple of parts.

As for the VFD, i'm not sure about the specs. I'll ask one of the hardware guys about the samsung units we use at work, but i'd imagine they'd pull more current than a LED... They just hook up to 3 of the I/O ports on our custom motherboard.

[xeron]

Hey.. samsung do some cool VFDs, actually. I was just going to use an alphanumeric, but looking here, i'm spoilt for choice :-D

I cant find any datasheets there, though, just simple tables. The only current ratings are for supply, not data...

[Stedy]

Hello,

I have put the schematic of the Clockport 24 bit I/O card online at:

http://www.ianstedman.co.uk/Downloads/clockport-dio-card.png

If you want more details, just ask.

Ian

[Castellen]

You could use shift registers to clock data in/out of the computer.
It depends on you using the data synchronously, which means you need to provide a clock signal in parallel to the serial data stream.

8 bit shift registers are easy to use, and if you require more than 8 inputs, then cascade them.  I.E. two of them in series will give you a total of 16 inputs.
You could probably use the joystick port for this, you can send data in/out of there in the same way the AirLink IR tranceiver works.

As for the display, personally I find serial LCDs a lot simpler to use, as the driver and everything is all built in.
You just need to send the correct setup and control information and you're in buisness.
Haven't played with them under AmigaOS, but have done using microcontrollers such as the Motorola HC11.  Using a PIC to do some of the work for you would make it even easier.  You could address it using asyncronous data via the serial port.

A few guys have used these in Amiga based car audio players.  See how they do it.  I saw some good circuit details on one of these sites.

[QuikSanz]

Actually the LCD & VFD use about the same power in watts, No backlight :-) However the VFD display needs a higher drive voltage. We use both on our entry phones.

Chris