Version 28 of serial ports on Windows

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 $com

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
 }

Yep, the above works fine on XP. Try " return lsort -dictionary $result" to get the list sorted... -regards

ZB 20111012 - yes, it works on my Win XP - but I had the problem, that id did list also the "virtual serial ports" left by Bluetooth device (not connected). Trying to open such serial port resulted in very long pause (almost a minute), before "open" gave up.

enumerate serial devices on win2k-win7(Jee Labs version [L1 ])

 # 2010-04-21 improved version, see http://talk.jeelabs.net/topic/208
 proc RawListSerialPorts {} {
   set result {}
   set ccs {HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet}
   foreach {type match} {
     Serenum {^FTDIBUS.*_6001.(\w+)}
     usbser  {^USB\B.*\B(.*)$}
   } {
     # ignore registry access errors
     catch {
       set enum "$ccs\\Services\\$type\\Enum"
       set n [registry get $enum Count]
       for {set i 0} {$i < $n} {incr i} {
         set desc [registry get $enum $i]
         if {[regexp $match $desc - serial]} {
           set p [registry get "$ccs\\Enum\\$desc\\Device Parameters" PortName]
           # Log . {usb-$serial Port: $p\
                     Friendly: [registry get "$ccs\\Enum\\$desc" FriendlyName]}
           lappend result usb-$serial $p
         }
       }
     }
   }
   return $result
 }

Note that you 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.

ZB The above procedure didn't work at all on my Win XP.

Category Device Control

Category Windows