What is on Your Mind?

Firstly I don't know where to put this so if it is the wrong forum then chastise me... ;oD

I built the hardware and wrote the software for an Audio Oscilloscope DC-100KHz in 2001 for the A1200(HD) via the AMIGA parallel port. It clocks the port at 200KHz, although 250KHz was easy enough via a 0.5 metre length of 25 core parallel cable. (I did successfully clock the port at around 500KHz but ONLY with direct connections to the port.

Full constructional details are on AMINET and if anyone wants to look I will post a pointer.

However I did do a GIF anim of the display and this is almost EXACTLY how it works.

Obviously I desgned the GUI for it and the push buttons when depressed, stay depressed until another range is required.

The unit ALWAYS defaults to 30V/Division AC and you cannot access the Y-Amp buttons until you press the VERT button first. This was for safety reasons.

EDIT:-
DOH!
I though I put this in "What's On Your Mind".
Sorry guys, if the Admin staff could move to that forum I would be grateful...
TIA.

AFAIK "What's On Your Mind" is as good a fit as any.

What prevents higher frequencies? Crosstalk?

Hi C688...

No. The clock speed. I made the 'scope with a 6 bit CA3306 A-D converter that was capable of 10MHz or better sampling rate. The data lines were dumped straight into the AMIGA parallel port via a 0.5 metre parallel cable. On a real 'scope this was easily visible...

The capacitance between the cable's data conductors and clock were _shunted_ to ground due to the capacitance above 250KHz giving erroneous readings, and, direct connection was not a goer due to the size of the end unit. The unit was hard wired on perforated board using terminal pins - no printed circuit at all.

Also there was a deliberate roll off at around 75KHz to help eliminate aliasing as the cut off freq approached clock speed.

It was ugly and big but was mainly for kids to practice soldering and basic engineering both electronic and mechanical. It required 2 off PP9 batteries too. OUCH!

It is still connected to my A1200 in my old computer room, but not switched on.

I also built a simple 10MHz frequency counter accurate to 100Hz to for the old tub too.
That is also on AMINET, uses stripboard instead though.

Done loads for the PC SPP and RS232 ports too, sooner or later they might come on here. ;o)

EDIT:-
The archive is in LHA format so I will try and post some piccies here of the CCT and construction.

Here you go; aspect ratio a little off but you get the idea...

Very nice. It's kind of a shame parallel port phased out when it did -- and that they only bothered making it fully bidirectional in its last, dying days. It was far and away the fastest protocol a hobbyist had for anything small or embedded.

The bizarre thing is it could not beat the AMIGAs port for both speed and flexibility. I only coded for SPP mode though, ECP and EPP modes I ignored as SPP was definitive for _all_ PCs at the time. You could actually FORCE bi-directionality on an IBM XT SPP but was a risky thing to do as damage to the port could occur; but it was possible. The XTs serial port was bomb proof. A have an AD converter built for the SPP along with 8086 assembly code to access it by grabbing two nibbles and creating a byte from them. Not particularly fast but well good enough for most applications.

See attached...

Hmm, just thought I still have my ancient quad core with an ECP parallel port. I wonder what it would be like using shell scripting to access the AD converter.

Gimme a bit of time and I will let you guys on here know...