[parisc-linux] Re: serial breakout box
Sat, 9 Feb 2002 09:53:36 -0800
On Mon, Feb 04, 2002 at 10:40:07AM -0800, firstname.lastname@example.org wrote:
> >>This is an Apollo 400 which has been upgraded to a 715T/50 (Trailways-50).
> > Pin 7 is GND. Pins 2 and 3 are the input and outputs, not necessarily
> > in that order. Measure from 7 to 2. Measure from 7 to 3. One
> > of them will be close to 0V. The other will be much higher. I think
> > -10V or something like that. The pin with the higher voltage is
> > the output.
> > Do the same thing on the other system also using the 25 pin connector.
> > Then make sure you are not connecting the output to the output.
> It turns out the Apollo 400 has a funky serial pinout.
> I obtained a breakout box and when I find the time, I will experiment with
> this strange serial port.
The Apollo 400 and the mouse are both "DCE". I can measure -11.44V on the
Apollo's pin 2 and on the PC's pin 3. I have verified that the mouse will
speak to my PC using only txd, rxd, and rts. I can also log into the
Apollo from the PC using only txd, rxd, and rts.
It is obvious the I need to connect the mouse's pins 2 and 3, to the
Apollo's pins 3 and 2. The rest is unsure. I have tried many combinations
of wiring, and I just haven't been able to get the mouse to work.
To connect two DCE devices, some suggest a "tail circuit cable". It seems
overkill to me since the mouse only uses a few pins. I have noticed that
the Apollo doesn't ever show voltage on the "carrier detect" pin. I have
also noticed that the Apollo voltage is -11.44 volts, and the PC voltage is
Can anyone give me tips for getting this mouse to work?