Serial Ports

  • Thread starter Thread starter Stewart Bell
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Stewart Bell

I have a device that transmits data via a serial cable.... My Computer has no
problem...But a client's transmitted data is trash... all cables are the same
all settings are the same. Either using an older Windows app or using
hyper-terminial
client data trash my computer everything fine.... Any Ideas ?
 
Stewart said:
I have a device that transmits data via a serial cable.... My Computer has no
problem...But a client's transmitted data is trash... all cables are the same
all settings are the same. Either using an older Windows app or using
hyper-terminial
client data trash my computer everything fine.... Any Ideas ?
Click to expand...

Is the client computer's serial port RS-232 compliant?
 
Stewart said:
I have a device that transmits data via a serial cable.... My Computer has no
problem...But a client's transmitted data is trash... all cables are the same
all settings are the same. Either using an older Windows app or using
hyper-terminial
client data trash my computer everything fine.... Any Ideas ?
Click to expand...
Can you give us an idea of what 'trash' means.
 
Stewart said:
I have a device that transmits data via a serial cable.... My Computer has no
problem...But a client's transmitted data is trash... all cables are the same
all settings are the same. Either using an older Windows app or using
hyper-terminial
client data trash my computer everything fine.... Any Ideas ?
Click to expand...

A baud rate mismatch can corrupt data. Normally, this
would be because of user error.

But a very long time ago, a baud rate mismatch could
also be caused by residual divider error in the baud rate
generator. The two devices then end up with a significant
error in the baud clocks they use. But your client's computer
probably isn't that crusty. (More of an issue 30 years ago.)

An RS-232 level shifter not pushing full levels, and the
usage of long data cabling, can also do it. Charge pump
based RS-232 level shifters cannot do as good a job as
the ones that run directly from +12V/-12V. But that only
becomes evident at high baud rates (>38.4K perhaps).

If you're running at 9600 baud, and using a short cable,
there are fewer good excuses. Maybe a bad cable, with a couple
conductors shorted together or something. Or a bad level
shifter, with a weak driver for the bipolar output.
An oscilloscope can be used to verify signal qualities.

Paul
 
Data from device should be ASCII like "1 5000.1212 5000.1414 300 Now" But
comes out "][] ]][[]] ][] ][][] " including control chars... All baud and
parity are the same I tried two different serial cables(Null Modem)...... All
works correctly on another computer ? No ActiveSynch loaded no phone..camera
software fax or modems installed..... Compter shows 1 Serial in Device
Manager.. Operation Normal (Correct One port on MB).. Tried all setting in
CMOS no change ?
 
Stewart said:
Data from device should be ASCII like "1 5000.1212 5000.1414 300 Now" But
comes out "][] ]][[]] ][] ][][] " including control chars... All baud and
parity are the same I tried two different serial cables(Null Modem)...... All
works correctly on another computer ? No ActiveSynch loaded no phone..camera
software fax or modems installed..... Compter shows 1 Serial in Device
Manager.. Operation Normal (Correct One port on MB).. Tried all setting in
CMOS no change ?
Click to expand...

Can you change the baud rate on the computer ? Try slowing the baud
rate setting down, without changing the device at the other end of
the link.

[ = 0x5B hex = 01011011 binary
] = 0x5D hex = 01011101 binary

Just a guess on my part, that the sampling device (the receiver)
is running too fast.

Paul
 
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