"Randy Day" wrote in message
...
In article ,
says...
[snip]
Sounds like some form of I2C; you'd have +v(piezo),
gnd, Clock and Data going to all 6.
No piezo on these cartridges, so Vcc, Gnd and I2C ??
Yes.
We can't rule out a proprietary setup, but I2C
is a strong possibility; it's built into a lot
of off-the-shelf microcontrollers, and only
needs 2 external resistors to operate.
We can't assume that the Vcc going to the
cartridges is used as Vcc for the I2C lines;
you'd have to measure the voltages on each
line.
I'm assuming that the 'chip' on each cartridge is a simple dedicated
microcontroller, so some level of Vcc would be required to run that, and it
would make sense to design the chip to run off a rail that would provide
suitable levels for the bus signals as well
I leave the logistics (of attaching a meter
and/or 'scope probe to a moving print head)
ENTIRELY to you! 
And I, in turn, leave this to Jeff L who has these things piled high
(literally !) at his place ... :-)
Arfa