This equipment (a Microgrid III 36" x 48" graphics digitizing tablet ca 1992)
is a tad esoteric at this point..no factory service, tech manual available,
etc. I'm a student trying to resurrect this old bird for my GIS classes.

Serial interfacing software (Vtablet) is available for connecting this to my
XP Pro Compaq laptop. I bought a serial port to USB adapter (Keyspan) for my
MGIII which self-installed at COM5. Since the COM1 port was occupied, I reset
the serial Keyspan adapter via the Windows Device Manager to COM2 and set
Vtablet to COM2 as well. Following recommended start-up procedure (Microgrid
tablet on, then boot) I am unable to elicit any puck output (screen cursor
movement in response to moving the puck on the tablet) which is also
confirmed as zero port interrupts on the software's Status tab.

I am now concerned that the tablet controller is misbehaving . I also note
that the Microgrid start-up only produces two tones instead of the €œall okay€�
three tone self-diagnostic (don't know the implication of the missing tone).

The unit has a removable 8" x 13" controller board and I was wondering if
anyone out there could direct me to an circuit troubleshooter who could look
it over and hopefully repair???

Many thanks!

"powerseed" u43512@uwe writes:

This equipment (a Microgrid III 36" x 48" graphics digitizing tablet ca 1992)
is a tad esoteric at this point..no factory service, tech manual available,
etc. I'm a student trying to resurrect this old bird for my GIS classes.

Serial interfacing software (Vtablet) is available for connecting this to my
XP Pro Compaq laptop. I bought a serial port to USB adapter (Keyspan) for my
MGIII which self-installed at COM5. Since the COM1 port was occupied, I reset
the serial Keyspan adapter via the Windows Device Manager to COM2 and set
Vtablet to COM2 as well. Following recommended start-up procedure (Microgrid
tablet on, then boot) I am unable to elicit any puck output (screen cursor
movement in response to moving the puck on the tablet) which is also
confirmed as zero port interrupts on the software's Status tab.

I am now concerned that the tablet controller is misbehaving . I also note
that the Microgrid start-up only produces two tones instead of the €œall okay€�
three tone self-diagnostic (don't know the implication of the missing tone).

The unit has a removable 8" x 13" controller board and I was wondering if
anyone out there could direct me to an circuit troubleshooter who could look
it over and hopefully repair???

First things to do would be to confirm

(1) that the serial port adapter has installed properly. I've used this or
a similar unit and the installation can be buggy especially when switching
to a different port. Either connect it to another PC with a known working
seerial port or select in a terminal emulator that is known to work with
COM5 and see if loopback works.

(2) that the tablet is actually outputting something on the serial port.
Make sure it either doesn't need any hand-shake signals (CTS, RTS, etc.)
or that they are set properly.

(3) that the cable has pins 2 and 3 swapped, or not swapped as required.
When connected correctly, there should probably be a negative voltage
on both pins 2 and 3 with respect to pin 5. If incorrect, then
there will be a voltage on only one of those pins.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

On Sat, 10 May 2008 14:08:01 GMT, "powerseed" u43512@uwe put finger
to keyboard and composed:

This equipment (a Microgrid III 36" x 48" graphics digitizing tablet ca 1992)
is a tad esoteric at this point..no factory service, tech manual available,
etc. I'm a student trying to resurrect this old bird for my GIS classes.

Serial interfacing software (Vtablet) is available for connecting this to my
XP Pro Compaq laptop. I bought a serial port to USB adapter (Keyspan) for my
MGIII which self-installed at COM5. Since the COM1 port was occupied, I reset
the serial Keyspan adapter via the Windows Device Manager to COM2 and set
Vtablet to COM2 as well. Following recommended start-up procedure (Microgrid
tablet on, then boot) I am unable to elicit any puck output (screen cursor
movement in response to moving the puck on the tablet) which is also
confirmed as zero port interrupts on the software's Status tab.

This is the user manual:
http://www.gtcocalcomp.com/files/Microgrid3.pdf

Make sure you have matched the communications parameters (baud rate,
parity, etc) at both ends of your cable.

Here are some recommended settings when used with Vtablet:
http://www.vtablet.com/download/Digitize.txt

To narrow down your problem, you could connect your tablet to a PC
with a real serial port and try this suite of test programs:
http://www.gtcocalcomp.com/files/sgdosdrv.exe

It includes an MGIII test.

Alternatively you could try a DOS terminal emulation program such as
Telix or Xtalk which can display incoming data in hex mode. You could
also set the tablet switches for ASCII output mode.

I am now concerned that the tablet controller is misbehaving . I also note
that the Microgrid start-up only produces two tones instead of the “all okay”
three tone self-diagnostic (don't know the implication of the missing tone).

The user manual says that anything less than 3 tones means your tablet
has a problem. On the plus side, the fact that it produces any tone at
all suggests that the CPU and ROM are probably OK.

If the PCB has socketed ICs, then you could remove them one at a time
to see if the error tones change. For example, if removing a RAM chip
changes your error report from 2 tones to 1 tone, then you can be
reasonably confident that your RAM is OK.

The unit has a removable 8" x 13" controller board and I was wondering if
anyone out there could direct me to an circuit troubleshooter who could look
it over and hopefully repair???

Can you upload a photo to your web space? It may jog my memory.

Many thanks!

You could try TabletWorks as an alternative to Vtablet:
http://www.gtcocalcomp.com/supportsummasoftware.htm

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Hi Sam...really appreciate your time and input!

Sam Goldwasser wrote:

First things to do would be to confirm

(1) that the serial port adapter has installed properly.

I don't have access to another PC w/ a serial port and am not a programmer
with familiarity with terminal mode (what can you expect from a clueless mac
user . I am pretty confident tho that this is a tablet problem as you may
concur after reading my following responses.

(2) that the tablet is actually outputting something on the serial port.

Serial port switches set to mfr's defaults re handshake, etc. I am also non
compos mentis when it comes to troubleshooting electronics but it did give it
a shot. I have a cheapo R. Shack digital auto-ranging digital multimeter
(that produces wandering phantom readings when not connected to a live
circuit). I tried to document output from the DB9 female on the serial
adapter with the board powered up. Nada when I put the black lead on P5
signal ground and the pos on P2 (during this test I was moving the puck and
pressing buttons as well). When I tested P5 and P2 it would momentarily show
0 volts as I was moving and clicking then it begin its up and down wandering
again???

(3) that the cable has pins 2 and 3 swapped, or not swapped as required.

I'm not using a serial cable...DB25 female plug to male DB25/female DB9
adapter to DB9/USB adapter to USB cable to PC

When connected correctly, there should probably be a negative voltage
on both pins 2 and 3 with respect to pin 5. If incorrect, then
there will be a voltage on only one of those pins.

See above...and my responses to Frank Zabkar in this thread.

My best,

Bill Curry

--
Message posted via http://www.electronicskb.com

Great to hear you have experience with tablets...and I appreciate the
mentoring very much!!

Franc Zabkar wrote:

This is the user manual:
http://www.gtcocalcomp.com/files/Microgrid3.pdf

Yep, had it.

Make sure you have matched the communications parameters (baud rate,
parity, etc) at both ends of your cable.

Here are some recommended settings when used with Vtablet:
http://www.vtablet.com/download/Digitize.txt

Vtablet settings at both ends.

To narrow down your problem, you could connect your tablet to a PC
with a real serial port and try this suite of test programs:
http://www.gtcocalcomp.com/files/sgdosdrv.exe

It includes an MGIII test.

This sounds like a great idea...will see I can find an old PC to test.

Alternatively you could try a DOS terminal emulation program such as
Telix or Xtalk which can display incoming data in hex mode. You could
also set the tablet switches for ASCII output mode.

This is beyond my PC skills at present;-)

The user manual says that anything less than 3 tones means your tablet
has a problem. On the plus side, the fact that it produces any tone at
all suggests that the CPU and ROM are probably OK.

If the PCB has socketed ICs, then you could remove them one at a time
to see if the error tones change. For example, if removing a RAM chip
changes your error report from 2 tones to 1 tone, then you can be
reasonably confident that your RAM is OK.

Looks like thru-hole soldering to me.

The unit has a removable 8" x 13" controller board and I was wondering if
anyone out there could direct me to an circuit troubleshooter who could look
it over and hopefully repair???

Can you upload a photo to your web space? It may jog my memory.

See http://www.powerseed.com/microgrid/Photos.html for pix you requested.

Other points:

**The left LED (yellow) on the puck is supposed to be on when the 16-button
cursor is in use, and off when the stylus is being used. It is alway off in
all my tests. The middle (green) LED is supposed to come on when the puck has
proximity (within the table's electromag field)--it always glows dimly when
the table is powered up. The third LED glows dimly all the time also...it's
for programmable alerts.

**The tablet came sans power supply. Based on the specs I picked up a 12volt,
1 amp supply. Manual says mfr's p.s. must be used or wtty is void. Is this a
possible issue?

**I note there are what appear to be contact tabs (labeled +12v AC, -12v,
+12v, +5v, DIG GND, DIG GND) at the bottom right (plan view). Are these for
test fixture powering?

**Misc.--Unknown variable...There are also two blue, 2-receptacle "pin
jumpers" (labeled W3 and W5) seen at the bottom center of the board (plan
view). Each jumper has two possible positions (left or right) among 3 pins.

You could try TabletWorks as an alternative to Vtablet:
http://www.gtcocalcomp.com/supportsummasoftware.htm

I did this a while ago with no response. Current s/w (Cartalinx, Clark Labs)
programmed for Vtablet.

Thanks Franc!

--
Message posted via http://www.electronicskb.com

On Mon, 12 May 2008 18:12:53 GMT, "powerseed via ElectronicsKB.com"
u43512@uwe put finger to keyboard and composed:

**The tablet came sans power supply. Based on the specs I picked up a 12volt,
1 amp supply. Manual says mfr's p.s. must be used or wtty is void. Is this a
possible issue?

Page 15 of the manual states that the tablet needs a 12V ***AC*** 1A
power supply. Instead you have provided a 12V ***DC*** 1A power pack.

**I note there are what appear to be contact tabs (labeled +12v AC, -12v,
+12v, +5v, DIG GND, DIG GND) at the bottom right (plan view). Are these for
test fixture powering?

Maybe. Measure them with a multimeter. I'm betting that the +12VAC
(???) and -12V rails will be missing. The -12V is required by the
tablet's serial port, and possibly by the analogue circuitry for the
digitizing surface, and for various op-amps.

I'm betting that the 2-tones error indicates a problem with the
analogue circuitry.

If you get your MG3 working, I would still run the MG3TEST. I've seen
lots of tablets with dead spots on the surface, usually caused by dry
solder joints, or bad driver chips (yours appears to use the ULN2003
chips).

BTW, if you ever need any spare ICs, keep me in mind. I have a lot of
chips of that era ... somewhere. You'll just need to pay for postage
from Australia. I also have a new unused 4-button Summagraphics puck,
but that cost me money.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

"powerseed via ElectronicsKB.com" u43512@uwe writes:

Hi Sam...really appreciate your time and input!

Sam Goldwasser wrote:

First things to do would be to confirm

(1) that the serial port adapter has installed properly.

I don't have access to another PC w/ a serial port and am not a programmer
with familiarity with terminal mode (what can you expect from a clueless mac
user . I am pretty confident tho that this is a tablet problem as you may
concur after reading my following responses.

(2) that the tablet is actually outputting something on the serial port.

Serial port switches set to mfr's defaults re handshake, etc. I am also non
compos mentis when it comes to troubleshooting electronics but it did give it
a shot. I have a cheapo R. Shack digital auto-ranging digital multimeter
(that produces wandering phantom readings when not connected to a live
circuit). I tried to document output from the DB9 female on the serial
adapter with the board powered up. Nada when I put the black lead on P5
signal ground and the pos on P2 (during this test I was moving the puck and
pressing buttons as well). When I tested P5 and P2 it would momentarily show
0 volts as I was moving and clicking then it begin its up and down wandering
again???

This sounds like it's doing something.

(3) that the cable has pins 2 and 3 swapped, or not swapped as required.

I'm not using a serial cable...DB25 female plug to male DB25/female DB9
adapter to DB9/USB adapter to USB cable to PC

When connected correctly, there should probably be a negative voltage
on both pins 2 and 3 with respect to pin 5. If incorrect, then
there will be a voltage on only one of those pins.

See above...and my responses to Frank Zabkar in this thread.

I'd go with checking the power supply/requirements as mentioned in
the other reply. Indeed, if it specifies 12 VAC, it probably won't work
correctly on 12 VDC (but won't be damaged either).

The fact that you're getting no change in the LEDs also suggests that
it's not a communications problem. Probably not getting through self
test due to the power issue.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

Franc Zabkar wrote:
**The tablet came sans power supply. Based on the specs I picked up a 12volt,
1 amp supply. Manual says mfr's p.s. must be used or wtty is void. Is this a
possible issue?

Page 15 of the manual states that the tablet needs a 12V ***AC*** 1A
power supply. Instead you have provided a 12V ***DC*** 1A power pack.

Oye-- How dumb is that!!! So this is just a step-down transformer!! I thought
all the bricks were AC to DC. Do you think using 12v DC could have hurt the
board? Or that it could be the source of my problems??? Not many of these
supplies out there. Did find one with a 3' cord though that I will pick up.

**I note there are what appear to be contact tabs (labeled +12v AC, -12v,
+12v, +5v, DIG GND, DIG GND) at the bottom right (plan view). Are these for
test fixture powering?

Maybe. Measure them with a multimeter. I'm betting that the +12VAC
(???) and -12V rails will be missing. The -12V is required by the
tablet's serial port, and possibly by the analogue circuitry for the
digitizing surface, and for various op-amps.

Didn't get any current when board was plugged into my !@$#$@% power supply--
perhaps AC will make a difference.

I'm betting that the 2-tones error indicates a problem with the
analogue circuitry.

I also saw at p. 40 of the UG that there are THREE MG3TEST diagnostic tests:
RAM, X-axis, and Y-axis--perhaps corresponding to the 3 tones??? Or not! If
so tho, might suggest Y-axis circuitry.

If you get your MG3 working, I would still run the MG3TEST. I've seen
lots of tablets with dead spots on the surface, usually caused by dry
solder joints, or bad driver chips (yours appears to use the ULN2003
chips).

One ULN2003...along with six UDN2595-A dips which I think are drivers.

BTW, if you ever need any spare ICs, keep me in mind. I have a lot of
chips of that era ... somewhere. You'll just need to pay for postage
from Australia. I also have a new unused 4-button Summagraphics puck,
but that cost me money.

Will keep all that in mind!

Thanks!

--
Message posted via ElectronicsKB.com
http://www.electronicskb.com/Uwe/For...epair/200805/1

Sam Goldwasser wrote:

I'd go with checking the power supply/requirements as mentioned in
the other reply. Indeed, if it specifies 12 VAC, it probably won't work
correctly on 12 VDC (but won't be damaged either).

The fact that you're getting no change in the LEDs also suggests that
it's not a communications problem. Probably not getting through self
test due to the power issue.

Yes...so will get the right power supply and see what happens. Will let you
know.

Thanks Sam!

Bill

--
Message posted via ElectronicsKB.com
http://www.electronicskb.com/Uwe/For...epair/200805/1

On Tue, 13 May 2008 01:57:41 GMT, "powerseed via ElectronicsKB.com"
u43512@uwe put finger to keyboard and composed:

Franc Zabkar wrote:
**The tablet came sans power supply. Based on the specs I picked up a 12volt,
1 amp supply. Manual says mfr's p.s. must be used or wtty is void. Is this a
possible issue?

Page 15 of the manual states that the tablet needs a 12V ***AC*** 1A
power supply. Instead you have provided a 12V ***DC*** 1A power pack.

Oye-- How dumb is that!!! So this is just a step-down transformer!! I thought
all the bricks were AC to DC. Do you think using 12v DC could have hurt the
board? Or that it could be the source of my problems???

As Sam has said, DC won't hurt your tablet. Using DC instead of AC
means that some negative voltages are not able to be generated within
the tablet for important functions such as the serial port and for
your signal amplifiers (op-amps).

I'm betting that the 2-tones error indicates a problem with the
analogue circuitry.

I also saw at p. 40 of the UG that there are THREE MG3TEST diagnostic tests:
RAM, X-axis, and Y-axis--perhaps corresponding to the 3 tones??? Or not! If
so tho, might suggest Y-axis circuitry.

I suspect that the power-up sequence starts with a basic digital test,
ie ROM/RAM/CPU check, after which the first tone is output. Then
perhaps the next level of circuitry is tested (eg the 2651 serial
controller chip), resulting in a second tone. The next and final set
of tests may involve the analogue circuitry, ie the X & Y wires, which
would fail in this case because of the missing -12V rail. But that's
just a WAG ...

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Franc and Sam...thanks for all the kind help! I'll let you know if the
12vac p.s. makes a diff. Fingers crossed!

Bill

--
Message posted via ElectronicsKB.com
http://www.electronicskb.com/Uwe/For...epair/200805/1

On Mon, 12 May 2008 17:28:30 GMT, "powerseed via ElectronicsKB.com"
u43512@uwe wrote:

I'm not using a serial cable...DB25 female plug to male DB25/female DB9
adapter to DB9/USB adapter to USB cable to PC

I would not expect regular function from this serial/USB adapters.
They can work, but it is not guaranteed

powerseed wrote:
Franc and Sam...thanks for all the kind help! I'll let you know if the
12vac p.s. makes a diff. Fingers crossed!

Hi Franc, Sam and Martin!

Well, I got my new 12v AC power supply! The plug was incompatible so I cut it
off and replaced it with one that fit. The great news now is that I get all
three required diagnostic startup tones and the green puck cursor LED blinks
on as it should whenever I move it out of proximity to the prescribed
electromagnetic digitizing area. Since it is showing proximity bounds around
the board perimeter, I assume it is reporting an x/y coordinate stream to the
board controller.

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

I am proceeding to troubleshoot the communication side now that the tablet
appears functional. Unfortunately when I plug in my serial to USB connection
per my previous post, no COM2 port activity is observed when I move the puck
and push buttons.

Switches: Firstly I rechecked my tablet switch settings to confirm they
matched the spec given with my Virtual Tablet software.

Interfacing Hardwa As I read it from their manual, the Summagraphics
tablet uses a three-wire, null modem interface with loop back handshaking.
They recommend a standard DB25(male) to DB9(female) converter/adapter cable.
I use a DB25/DE9 converter plug into the female DB25 table port A instead of
a cable. I checked male/female continuity on this adapter plug to insure it
was a null modem configuration...2 on DB25 to 3 on DE9, and 3 on DB25 to 2 on
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.

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
Pin 3 to Pin 7: -5.8 volts DC

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

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,
7&8=RTS/CTS, 9=ring). One first installs the Keyspan driver software and then
the adapter is connected to the PC via USB cable. The doc says that upon
plugging in the Keyspan, it will take the first open port after those that
have been assigned or set aside. It auto-installs at COM5. Problem here is
that the Virtual Tablet software only allows connections via COM1 through
COM4. Device Manager only shows COM1 taken for the modem.

Using a Keyspan utility program, I reassigned the Keyspan to COM2 and Device
Manager recognizes it at COM2 as available. Keyspan diagnostic software has a
port test function and it passed €œtransmit only€� and €œinternal loop back€�
tests. I assume this means its functioning properly in COM2. I €˜ll have to
get a DE9 serial loopback connector before I can run the €œexternal loopback€�
test.

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
€œBusy€�. Another diagnostic provides status reports (driver event and data
monitoring). It shows streaming driver events and no data activity. The
Tablet Manager software was also set to COM2 and its status page also shows
no data transmission activity.


At this point I am stymied but, per your recommendation, I did get an old PC
laptop that has a real DE9 COM port. I need to pick up an adapter cable
before I can test the tablet in this manner with the Summagraphics MGIIItest
software.

The Keyspan doc doesnt show any way to set comm params such as baud, parity,
stop bits, etc. on the computer end. Since the tablet uses two stop bits
would this screw up flow if the Keyspan is operating on a one stop bit
default???

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

--
Message posted via ElectronicsKB.com
http://www.electronicskb.com/Uwe/For...epair/200805/1

On Mon, 19 May 2008 01:56:09 GMT, "powerseed via ElectronicsKB.com"
u43512@uwe put finger to keyboard and composed:

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
per my previous post, no COM2 port activity is observed when I move the puck
and push buttons.

Switches: Firstly I rechecked my tablet switch settings to confirm they
matched the spec given with my Virtual Tablet software.

Interfacing Hardwa As I read it from their manual, the Summagraphics
tablet uses a three-wire, null modem interface with loop back handshaking.
They recommend a standard DB25(male) to DB9(female) converter/adapter cable.
I use a DB25/DE9 converter plug into the female DB25 table port A instead of
a cable. I checked male/female continuity on this adapter plug to insure it
was a null modem configuration...2 on DB25 to 3 on DE9, and 3 on DB25 to 2 on
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,
7&8=RTS/CTS, 9=ring). One first installs the Keyspan driver software and then
the adapter is connected to the PC via USB cable. The doc says that upon
plugging in the Keyspan, it will take the first open port after those that
have been assigned or set aside. It auto-installs at COM5. Problem here is
that the Virtual Tablet software only allows connections via COM1 through
COM4. Device Manager only shows COM1 taken for the modem.

Using a Keyspan utility program, I reassigned the Keyspan to COM2 and Device
Manager recognizes it at COM2 as available. Keyspan diagnostic software has a
port test function and it passed “transmit only” and “internal loop back”
tests. I assume this means its functioning properly in COM2. I ‘ll have to
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
Tablet Manager software was also set to COM2 and it’s status page also shows
no data transmission activity.


At this point I am stymied but, per your recommendation, I did get an old PC
laptop that has a real DE9 COM port. I need to pick up an adapter cable
before I can test the tablet in this manner with the Summagraphics MGIIItest
software.

The Keyspan doc doesn’t show any way to set comm params such as baud, parity,
stop bits, etc. on the computer end. Since the tablet uses two stop bits
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
--
Please remove one 'i' from my address when replying by email.

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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