serial port interfaced EEPROM reader no longer detected after temporaryremoval

M

Margo Guda

I have an EEPROM reader that connects through a serial port, of which
(according to device manager) I have only one on my xp pro sp2 system.
This is supposedly COM1.
I had to remove this reader for a few minutes (to test on another
computer), which I did; when I put it back on its original system, the
software used for getting data off it no longer recognizes it.
I checked the device manager for the port it connects to, it is COM1
which shows as the only serial port (other than the plethora of USB
ports available), but when I look at port settings, I see something
under COM2 as in use. I am not aware of anything that could be using
COM2, which does not show up on the device manager. I don't have a phone
modem anymore, so what can be happening?
Can anybody tell me how to make my device visible to its data reader
again? Help would be much appreciated.

Margo Guda.
 
G

Ghostrider

Margo said:
I have an EEPROM reader that connects through a serial port, of which
(according to device manager) I have only one on my xp pro sp2 system.
This is supposedly COM1.
I had to remove this reader for a few minutes (to test on another
computer), which I did; when I put it back on its original system, the
software used for getting data off it no longer recognizes it.
I checked the device manager for the port it connects to, it is COM1
which shows as the only serial port (other than the plethora of USB
ports available), but when I look at port settings, I see something
under COM2 as in use. I am not aware of anything that could be using
COM2, which does not show up on the device manager. I don't have a phone
modem anymore, so what can be happening?
Can anybody tell me how to make my device visible to its data reader
again? Help would be much appreciated.

Margo Guda.
Click to expand...

The COM (or serial) port might not be hot-swappable. Shut down and start
up the computer with the EPROM reader re-attached.
 
B

Bob I

Hopefully, you didn't damage it "hotplugging" it. Perhap going through a
uninstall, reinstall will get it recognized again. It may be that the
COM2 was assigned because COM1 was in use.
 
M

Margo Guda

Can the serial port be damaged by hotplugging?
What I did was this: the reader has a pluggable cable that goes into a
telephone-style connector on its side, and a ninepin RS232 on the other.
I unplugged the reader end.
I have since tried to uninstall the port (does not work; I have to
reboot the machine and when it does, the com1 is right back where it
was), powered down the reader (it has its own power supply) and rebooted
the computer various ways, with the reader off (its normal state) and
with the reader on. None of those makes any difference. It will not
interface with the computer. And I don't have anything else to test the
port with. The device manager says it's working correctly.
 
P

Paul

Margo said:
Can the serial port be damaged by hotplugging?
What I did was this: the reader has a pluggable cable that goes into a
telephone-style connector on its side, and a ninepin RS232 on the other.
I unplugged the reader end.
I have since tried to uninstall the port (does not work; I have to
reboot the machine and when it does, the com1 is right back where it
was), powered down the reader (it has its own power supply) and rebooted
the computer various ways, with the reader off (its normal state) and
with the reader on. None of those makes any difference. It will not
interface with the computer. And I don't have anything else to test the
port with. The device manager says it's working correctly.
Click to expand...

If a computer has two serial ports, you can use one serial port to test the
other serial port. You need a "null modem" or crossover cable, so the TX pin
on one connector, goes to the RX pin on the other connector. With the two
COM ports set to the same baud rate and stop bits etc, you use Hyperterminal
to type characters in one screen, and see them appear, received, on a
second Hyperterminal window. That is how you'd test with two serial ports.

You could also loop the TX signal to the RX signal on the serial connector,
and then, using Hyperterminal, you'd look for the echoed characters. To do
that, I'd probably use a Dsub connector, and solder a wire between 2 and 3 or
whatever the pinout happens to be for the connector in question.

So you don't necessarily need another gizmo, to do some testing of a serial
port. In the second test case, you need a means of connecting pin 2 to pin 3,
but in a pinch, a second human can hold a conductor against the two pins
in question, while you do some test typing in Hyperterminal. You don't absolutely
need to make up a test connector to loop pin 2 to pin 3.

Paul
 
B

Bob I

Serial ports were not designed to be hot plugged, but people "generally"
get away with it. What port is the software looking at for the reader?
Does the system claim that the COM1 is in use?
 
M

Margo Guda

Bob said:
Serial ports were not designed to be hot plugged, but people "generally"
get away with it. What port is the software looking at for the reader?
Does the system claim that the COM1 is in use?
Click to expand...
The software is looking for COM1. I opened its properties sheet in
device manager, and it shows working correctly as the status. In the
advanced options I looked at the possibility to rename the port, and
noticed that COM2 has (in use) behind it, but as far as I know I don't
have COM2 on my system.
The manufacturer of the EEPROM reader tells me that the software scans
for available serial ports (1 through 4) and you can set one that is
available. I've tried that on another computer (not my own) and it
worked. But in this case I cannot get it to work.
I also tried using a serial-to-usb converter, but so far no luck: I
borrowed one, that is supposed to come without drivers, and windows
tried to find a driver for it and failed. It went on the net to look for
a driver and says it cannot find a driver. The person who lent me the
plug says it did not come with a driver. Any ideas?
 
B

Bob I

Interesting. I wonder if the original instance of COM1 got set to be
COM2? Remove both COM1 and COM2, and then restart. You should come up
with a single working COM1 after new hardware found is done. This is a
frequent occurrence/problem with USB/Serial ports.
 
M

Margo Guda

But the craziest thing is that nowhere do I see COM2 except in the
rename option for COM1. And, when I try to remove COM1, what happens is
this: device manager tells me to reboot the machine, I do, and when I
come back up for air there is COM1 in the device manager, working
correctly as if I never did anything. No found new hardware dialog
either. It's as if it was never deleted. My only other option, to say No
after it asks me if I want to reboot, seems not to do anything.
 
B

Bob I

Is this on the motherboard where you can diable it in the BIOS? Another
thing you may try is the "MODE" command at the CMD prompt, using MODE
you may read what the COM is configured as, and issue MODE commands to
chand the bitrate stopbits etc. and then verify that it is reacting.
 
M

Margo Guda

I never tried the BIOS! That's what I'll try next. However, I did try
the mode command. It says COM1 is not currently available; gives the
correct parameters for COM3, and (just checking) says COM2 and COM4 are
illegal device names. Do I interpret correctly that COM1 is disabled
(even though it shows enabled in the device manager), COM3 has been
correctly installed by the serial-to-usb converter, and the other two
are just not on my system?
I have now managed, BTW, to get the software for the reader to recognize
COM3 and use it. What I did was first remove COM1 in devman, not
rebooting (now it let me, and did remove COM1) and then rescanning for
hardware, bringing COM1 back. Somehow, in this sequence, the reader
software indeed recognized the box on COM3, which seems to be the only
WORKING serial port on my system right now. So I'm glad I can get my
data, and will try the BIOS settings next & see if it somehow got
disabled on the board.
Thanks for your help.
 
M

Margo Guda

OK I checked this, and on my BIOS settings program you cannot do
anything with the ports, other than set their address in memory. No
enabling or disabling, at least I couldn't find anything like that, and
I looked at all the options.
What does it mean that the mode com1 command gives me com1 is not
currently available?
Thanks...
 
B

Bob I

COM3 and COM1 use the same IRQ number (4) but different adresses,
normally COM1 and COM3 are not available at the same time. If your
software is happy using COM3 just go ahead and use it that way, the
result should be exactly the same.
 
B

Bob I

That COM3 is in it's place.

Margo said:
OK I checked this, and on my BIOS settings program you cannot do
anything with the ports, other than set their address in memory. No
enabling or disabling, at least I couldn't find anything like that, and
I looked at all the options.
What does it mean that the mode com1 command gives me com1 is not
currently available?
Thanks...
Click to expand...
 

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments. After that, you can post your question and our members will help you out.

Ask a Question

Similar Threads

COM port not opening 1
USB to serial port 3
Legacy serial ports 12
Serial Ports Not Accessable... 2
PCI Serial Card 16
COM1 not behaving... 21
How Do I Configure Serial Port Correctly? 10
Device Manager > Non-Plug and Play Drivers > Parallel port driverAND Serial 2

Top