18 Jun
2013
18 Jun
'13
11:25 a.m.
Depending on what it's to be connected to, I could
come pretty close to
an async serial interface using discrete transistors. I'd need a lot
You can. There must have been a Teletye interface for the straight-8, for
example.
of them, probably nearly a hundred by the time
it's all done, but it's
not out of reach. USB probably _is_ out of reach.
It's fairly straightforward. The 3 wire handshake needs a bit of logic,
but it can be done as a state machine with 2 or 3 flip-flops and a
handful of gates. Take a look at the HP59405 schematic (on
http://www.hpmuseum.net/) which is the HPIB (much the same as IEEE-488)
interface for the HP9830. It's about 20 TTL ICs, even including the bus
interface to the HP9830 (which will acouunt for 3 or 3 of them).
I don't know how easy it is to find the schematics of the early HPIB
peripehrals on-line, but the HP59306 relay box drives 6 relays from
ASCII-encoded messages (Things like 'A1' to set relay 1 to staate A,
'B34' to set relays 3 and 4 to state B, etc) sent over HPIB. It's pretty
simple inside, perhaps 15 or 20 TTL ICs.
-tony
And when things don't work, it's a lot
harder to make sense of the
signals on a USB cable than those on an RS232 or IEEE488 cable.
Dunno 488, never done much with that. But 232, yeah. Indeed, crank