I don't have a lot of debug equipment. Make that none. An oscilloscope
is on the list of things to learn and purchase.
I am well versed in serial communications, and used a breakout box and a
multimeter. I confirmed the pinout on the connector, and used the
frequency counter feature of the meter to see if the bits for the data
lines were wiggling - nothing. In that case, I don't think a better
tool is going to tell me more.
I remember that I traced it back to the 8031 derivative, and that seemed
to be the source of the problem. It was holding all of the data pins
either high or low. The data pins in turn were fed to a Maxim IC to get
them to proper serial levels, but by then it was too late .. bad input
equals bad output.
Details can be found in the list archives .. it was just this past summer.
Ethan Dicks wrote:
On Thu, Feb 14, 2008 at 11:47:34PM -0600, Michael B.
The protocol is explained on the referenced
'codeninja' page, but I
never got my samples of the 6094 to talk. They seem to function in
stand-alone mode (lights will change when a key is pressed), but nothing
ever comes across the serial connection to a PC.
I've tried a variety of cables, breakout boxes, multimeters, etc. I'd
love it if somebody else tried and tell me what I am doing wrong.
Even if we get the lot to distribute amongst list members (I'm in!),
I wouldn't be able to lay my hands on one until October. In the meantime,
for the one that you have now, have you tried a serial analyzer like
an HP4951? They sit between a computer and a modem/terminal, or between
any two devices, and can snoop traffic in both directions. You also
have the ability, as a standalone device, to program a limited amount
of protocol traffic, enough so that we were able to simulate the BIND
for an SNA session, and keep the PU Type 2 device on the far end thinking
it was still connected to a PU Type 4. That was the max we could do -
there wasn't enough programmable memory to allow a real session, but it
does illustrate the point.
You could also try an oscilloscope - for a single key press (no repeat?),
a storage scope might work better, or a real logic analyzer - to capture
the bit stream, just to see it.
Those are the sorts of tools _I_ use when I'm snooping strange serial
streams. Dunno what you have on hand.