[time-nuts] Frequency Counter Choice

[Oz-in-DFW]

On 10/22/2020 11:52 AM, jimlux wrote:
>  I wonder if one could implement the protocol using GPIO pins on
> something like a Beagleboard or Arduino clone?
>
> (yes, as a product, with the right connector and line
> driver/receivers, etc. - it would cost the same as a Prologix... but
> as a hack...)
>
> After all GPIB is a very old standard, and was developed back in the
> day of 1 MHz logic. I think you could do the handshaking in software -
> punch the bits one by one, assert DAV, etc.
> Listener reads bits one by one, then asserts the ACK or NAK
Actually it's bytes.  It's byte-serial not bit serial.

Most modern micros can pretty easily keep up with the bus - especially
if you use GPIOs that can generate interrupts. The only real challenges
are finding a reliable source of the appropriate connector - and driving
the 5V lines at the current levels required for a loaded bus.  Most
modern micros do not have 5V tolerant I/O but that's pretty easily dealt
with. Connectors can be had, NORCOMP's 112 series should be ideal.
https://www.norcomp.net/series/112-series and are available through
DigiKey, Mouser, Farnell, etc. TI's SN75160/SN75161 bus transceivers
still seem to be in production as SOICs as well.

I've noodled about building a board that was intended to connect to a
single instrument, but not really gotten serious about it.  I wanted
everything in the shop on Ethernet.

Oz (in DFW)