Re: USB, 1394, PCI, ISA, IDE ??

[Jon Elson <jmelson-at-artsci.wustl.edu>]

Ray Henry wrote:

> The developing TclTk iosh and tkio will soon make it possible for us to do
> great things with this kind of PLC level machine control.  We may even be
> able to write some tiny RT PLC SHMEM routines that we can launch with Tk
> for time critical machine control tasks.

I have an idea to run an automated lube system, based on total travel on
each axis since the last lube application.  I have already made a lube
distributor valve, but am doing it manually, right now.

> Perhaps those who know these things could compare the relative costs in
> hardware to develop firewire vs parallel port.  We would also need some
> sense of the software effort that it would take to make each fit into EMC
> and the speed at which each would be expected to work.

I already have a board designed to enable up to 256 'modules', with up to
256 (8-bit) registers per module, to be accessed from the parallel port.
We are using this to run a number of instruments at work.  It uses 4 ordinary
LS TTL chips, plus two resistor packs for termination.

The only problem with this is that it takes several cycles to select a module,
select a register, and send to or receive data from it.  This is not bad,
except that the access must be serialized to prevent one program from
changing the address while another program is reading or writing data.

The 'driver' is VERY simple, just a couple lines of code.
I'd be glad to make this design available to the group, if there is interest.
The proprietary bus on the far end of this adapter is a 26-conductor
ribbon cable.

Jon