[time-nuts] Arduino GPIB

[Joseph Gray]

I thought everyone here would find this of interest. I stumbled across it a
few days ago on the 'net. It is a Prologix GPIB-USB compatible made with an
Arduino Uno.

http://egirland.blogspot.com/2014/03/arduino-uno-as-usb-to-gpib-controller.html

Like on his web site, I just took a cheap GPIB cable, cut off about 12
inches and shoved the wires into the socket holes on an Uno. I uploaded his
program and did some minor testing so far. BTW, it didn't work the first
time due to poor contact. I shoved some pin headers in, after the wires and
now it works fine.

John's Prologix config program works just fine with this cobbled together
GPIB adapter. I attached it to my HP 3457A and then ran the demo program
that comes with Ulrich's EZGPIB. It is logging data as I type this. I will
do more testing with other instruments, as I have time.

As mentioned on the web page linked above, a few commands are not yet
implemented, although they appear to be little used commands (except
perhaps the ++savecfg command). I think I have a way to implement the ++rst
command using the watchdog timer. For ++savecfg, it shouldn't be too
difficult to store things in the Arduino EEPROM.

I have some cheap Arduino Nano's and PCB-mount GPIB connectors on order. I
will be making a couple of these Proligix-compatible adapters with those
parts, so that they aren't just wires shoved into a board. I'll have to
find a small box to house things. I have also ordered some buffer chips to
add to the design. Total cost should be under $20 for each adapter.

The firmware uses a serial baud rate of 115200, which I assume is the same
as a real Prologix. I'm going to try some higher baud rates to see how fast
the Arduino can push bits without losing them. I understand that with the
default 16 MHz clock, non-standard baud rates that are evenly divisible
into the clock rate should work even better I'll report back.

One question about the baud rate - are there any reasons not to change from
115200? Since we are simply moving bits through a USB/Serial adapter, does
any software really care what the baud rate is, as long as we don't drop
any bits?

Joe Gray
W5JG