serial port, paired device...
lazarus / 35-Windows CE

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mmikac · 2010-05-14 18:39

I have to manage detection when serial (print) device is off (automtic
power down for example).
However, when I define permanent paired connection between IPAQ and
this device, neither I get any exception when trying to write to
temporaray unavailable device, neither anything else..

(I tried to use 1. try..except on assignfile to com port and
rewrite/writeln, 2. ioresult with $i-/$i+ directives, 3. fileexists()
...)

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felipemdc · 2010-05-20 15:55

Maybe you could show some code to make more clear what you are doing.

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Lazlover · 2010-05-20 16:26

RTS/CTS is the "standard way" to detect if device is ready to accept
input.

If you use only tx & rx-lines without any HW-handshake there is "no
way" to detect before you send anything..

Then the "only" option is ask the device if it's alive..
eg. like sending command AT to a modem, you get back OK.. Then you
know.

Edit: Ahh.. I see now, you want to detect if the local device is still
there, not if the extrernal device is alive.. Sorry..

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mas steindorff · 2010-05-20 19:50

I found a (good) unit already writen for the serial port called
Synapse writen by Lukas Gebauer Found at URL:
http://www.ararat.cz/synapse
It uses the Windows registry to determine which ports are active in
Windows under the /HARDWARE\DEVICEMAP\SERIALCOMM' key in the
"HKEY_LOCAL_MACHINE" root.
For Linux the funtion just returns the result of
'/dev/ttyS0,/dev/ttyS1,/dev/ttyS2,/dev/ttyS3'

The Windows device drivers will update the registry anytime they
detect new hardware like a USB serial device. There is another key
somewhere in the registry that list all of the ports that have ever
been connected not that it's not what you're looking for