Disclaimer: I am not an EE and I don't even play one on TV. That said, I
have done similar things plenty of times, as my uC of choice is CMOS (3.3V).
I would supply the chip with 5V and then use a 1k resistors to the pins of
the uC. I have a bunch of stuff running like that and so far have never
blown a uC pin doing so. Some things won't work like that but I have never
trashed a part trying.
However, YMMV and don't cry if it doesn't work or blows a pin.
Jonathan
The simplest solution I can think of is supplying both chips with 3.3V
and hoping for the best. Altough I don't read russian, I can tell from
the data sheet that the logic levels should match surpricinly well,
but I cannot tell whether the rest of the circuit functions properly
with a lower than expected supply voltage. I have limited capabilities
to test the circuit properly (with nixies, cathode driver and
microcontroller etc.) and therefore I wonder if anyone at Neonixie has
used the K155ID1 like this before. I guess that the question is pretty
generic really; is it possible to run a (early generation) TTL circuit
at 3.3V reliably? Keep in mind that I don't require very quick
switching, kilohertz are just fine here.
The next step would be to add a 5V-regulator just to feed the driver.
In that case, how/do I need to protect the outputs of the
microcontroller? I have looked into the 'standard' schematics for TTL
and it seems to me that a TTL input with a 5V supply would tend to
pull its input high, possibly destroying a 3.3V output. Is series
resistors sufficient or are transistors needed too?
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