Hey Franc and others...

Finally! Made the connection!!! Was a cabling issue I was able to unravel.
Thanks for all the fine and generous help!

Bill

Franc Zabkar wrote:
Q: Do I have to be concerned about plug polarity with this 12V AC power
supply?

No. There is no polarity.

I am proceeding to troubleshoot the communication side now that the tablet
appears functional. Unfortunately when I plug in my serial to USB connection
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DE9. The DE9 female of the converter plug is connected to the male DE9 of a
Keyspan serial port adapter which is USB cabled to my Compaq laptop.

Pin 2 of the 9-pin connector is an input (Rx) to the PC, pin 3 is an
output (Tx).

Output Voltages: With my crappo multi-meter I first checked the DC voltage of
the DB25 female serial port A on the tablet, particularly, the TX (2)/RX(3)
pins compared to signal ground (7).

Pin 2 to Pin 7: variable 0.7 to 1.4 volts DC

That's the voltage (floating) which one would expect on an input pin.

Pin 3 to Pin 7: -5.8 volts DC

That's what you would expect on an output pin.

So it appears that your Tx and Rx pins are correctly wired. Your
tablet is configured as a DCE (data communication equipment), not a
DTE (data terminal equipment).

Q: Does this imply the tablet is streaming data out?

You need to measure the pins when the puck is off the surface, and
then again when the puck is in proximity.

COM port assignment: The Keyspan USB/DB9 male serial adapter has DB9 pin-outs
analogous to a DB9 socket on a PC (23=RX, 3=TX, 5+GND, 4&6=DTR/DSR,
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get a DE9 serial loopback connector before I can run the “external loopback”
test.

Just short pins 2 and 3 (with a screwdriver?) and access the port
using a terminal program such as HyperTerminal. Disable local echo and
then type any key. If the port is working you should see your typing
being echoed on your screen.

When I plug the keyspan into the tablet, power up the tablet and then boot
the PC, the Keyspan port mapping diagnostic show the adapter on COM2 and
“Busy”.

Maybe the RTS/CTS/DTR pins are in the wrong state. You should measure
them with your multimeter. An RS232 breakout box might be handy.

Another diagnostic provides status reports (driver event and data
monitoring). It shows streaming driver events and no data activity. The
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would this screw up flow if the Keyspan is operating on a one stop bit
default???

Probably.

Sorry for the data dump but I wanted to give you all my observations in hope
that you may have some further insights to assist me. Thanks to all!

Bill Curry

I wrote the following COM port testing utility to help me test the
various RS232C signals:
http://www.users.on.net/~fzabkar/comstest.exe

It should also help you determine how your cable is wired, ie which
pins are looped back to others. The program runs under DOS and only
works with real COM ports.

- Franc Zabkar

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