Serial Ports on Windows
I created this page in case some people may have some questions or answers about using a serial port on Windows.
I just tried to communicate with com1 on a Windows 2000 machine. For some reason I could not receive any data using the following commands in Wish.
% proc rd_chid {chid} {
set msg [gets $chid]
puts $msg
}
% set com [open com1: r+]
% fconfigure $com -mode 9600,n,8,1 -blocking 0 -translation auto -buffering line
% fileevent $com readable [list rd_chid $com]However, I was able to receive data by putting those last 3 lines into its own procedure...
% proc rd_chid {chid} {
set msg [gets $chid]
puts $msg
}
% proc open_com {} {
global com
set com [open com1: r+]
fconfigure $com -mode 9600,n,8,1 -blocking 0 -translation auto -buffering line
fileevent $com readable [list rd_chid $com]
}
% open_com
# lots of data comes streaming :)
% close $comjg
Tcl 8.4 greatly improved serial port control across platforms. Refer to the updated fconfigure documentation for more info.
To retrieve details on input/output errors--which are, in general, frequent, when working with serial lines--interrogate
set details [fconfigure $serial_handle -lasterror]
8.3.4 introduced this capability.
How can I connect to a com port higher than 9? (I am using a terminal server, and its driver creates com ports upto 16 or so.) Would appreciate answer by mail - [email protected]
Thanks
25Aug2003 PS: You need to use the 'generic' name (I think it is actually the UNC path) of the com port. Use the file name \\.\com13 to open 'com13:' Mind you, windows wants to see those all those \ chars, so use [open \\\\.\\com13 r+]. I have not tested this myself... E_NO_ACCESS_TO_BIG_SERIAL_CARD. But it does work :)
The following code will enumerate the serial devices on a windows XP machine - including USB devices.
package require registry
proc get_serial_ports { } {
set serial_base "HKEY_LOCAL_MACHINE\\HARDWARE\\DEVICEMAP\\SERIALCOMM"
set values [ registry values $serial_base ]
set result {}
foreach valueName $values {
lappend result [ registry get $serial_base $valueName ]
}
return $result
}Also note that you want:
set serial [open "COM1:" "RDWR"]
and not
set serial [open "COM1" "RDWR"]
without that colon (:), you get a file in the current directory called COM1. Also, note that you will most frequently see code something like this:
set serial [open "COM1:" "RDWR"] fconfigure $serial -mode 9600,n,8,1
where fconfigure sets the baud rate, etc. of the serial port.