>> I suspect the keyboard is seeing the characters you are sending
>> as commands to the keyboard, but as it doesn't know what to do
>> with them it goes into dumb mode

Alan,

I'll double-check all signals when I'm at that PC tomorrow. There
is a protocol for the PC to request the keyboard accept data

>From the specs -

"If the keyboard is not sending or if the system elects to override the
keyboard's output, the system forces the keyboard clock line to low
level for more than 60 microseconds while preparing to send data.
When the system is ready to send the start bit (the data line will be
low), it allows the clock line to go to high level"

Now, re-reading that, possibly I'm looking at the wrong end of the
PIC's data packet. I do send the clock line low for > 60us, and that's
at the end of the transmission, after the Stop bit. However, the 4066
should be isolating the keyboard from that. But it's worth checking,
maybe there's leakage. I'm wondering why my keyboard (the waveform
of which I copied) has that 357us low on the clock line after the Stop
bit. I don't see it in the specifications. Perhaps reducing it to a nominal
bit width will fix the problem, without needing the 4066

> Barcode readers designed to be used between a PC keyboard
> and a PC, uses a "Wedge". Now, I do not think that thing
> simply hard-wires the in and out connectors as in this case.
> I'm pretty certain that it contains some electronics to isolate
> interfaces

Jan-Erik,

If so, those electronics would have to allow the bi-directionality of
the lines

Joe

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