Re: USB to IEC

Den Sat, 4 Jan 2020 07:18:27 +0000 skrev "Baltissen, GJPAA (Ruud)"
<ruud.baltissen_at_apg.nl>:
> Hallo allemaal,
> 
> 
> > ... PI ... Arduino ...
> 
> The problem, or more precise, my problem with the PI is its 3.3V I/O
> interface. When interfacing to 5V I/O, there are always these voltage
> convertors needed. The Arduino doesn't have this problem. I just
> bought the Mega256 to see what is possible. And I also found a
> project that does the some basic things so I don't have to start from
> scratch. 

Well, IEEE-488 really needs stronger drivers than what I assume an
Arduino can do, so you anyway need some external chips to interface a
PI or an Arduino with IEEE-488. At least if you want it to work on a
chain with more than just a PET and nothing else.

I haven't really dived into it that much, but it's probably possible to
replace the common 75160 and 75161 with something else that's a more
commonly available chip (not that they are super hard to obtain or so,
but still). If doing that, you might go for something that's 3.3V
compatible.

Btw the level converters Raj Wurttemberg linked to will damage the PI
after a while if using more than one device on the IEC bus (in addition
to the PI), so for example combining a PI1541 with a real 1541 should
be done with the unidirectional active level converters instead of
those passive-ish bidirectional converters.

> > it would be simple to add an ATN trap.
> 
> That is a must as I found out with my own CBM-HD. What is also a must
> is that ATN is connected to an INT line. Some years ago somebody
> showed a self-made device that was accepted by a CBM and 8250 but my
> CBM-HD had problems with it. This ATN/INT thing solved the problem.
> Just my two cents...

Well, with an ATN trap you could get away with no interrupt as the
timeout is iirc infinite on the computer. An interrupt would of course
still be a good idea.

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