Opening a serialport, transmitting on txd, dtr and rts - serial-port

Question

Morning all,
I have developed an app with C# and Windows Forms that opens a serialport and transmits on txd, dtr and rts.
I want to be able to do this with tcl/tk but finding serialport tutorials on tcl/tk is proving quite difficult. I did find something on Stackoverflow Here. But when running it:
It says "couldn't open serial "COM7": permission denied"
Does anyone know why permission is denied and how to grant permission? Also does this code even work.
Does anyone have any sample code I can try or can point me to a good understandable source please?

Answer 1

You could have a look at this example that uses a Tcl/tk to read data from a serial port:
############################################
# A first quick test if you have a modem
# open com2: for reading and writing
# For UNIX'es use the appropriate devices /dev/xxx
set serial [open com2: r+]
# setup the baud rate, check it for your configuration
fconfigure $serial -mode "9600,n,8,1"
# don't block on read, don't buffer output
fconfigure $serial -blocking 0 -buffering none
# Send some AT-command to your modem
puts -nonewline $serial "AT\r"
# Give your modem some time, then read the answer
after 100
puts "Modem echo: [read $serial]"
############################################
# Example (1): Poll the comport periodically
set serial [open com2: r+]
fconfigure $serial -mode "9600,n,8,1"
fconfigure $serial -blocking 0 -buffering none
while {1} {
set data [read $serial] ;# read ALL incoming bytes
set size [string length $data] ;# number of received byte, may be 0
if { $size } {
puts "received $size bytes: $data"
} else {
puts "<no data>"
update ;# Display output, allow to close wish-window
}
############################################
# Example (2): Fileevents
set serial [open com2: r+]
fconfigure $serial -mode "9600,n,8,1" -blocking 0 -buffering none -translation binary
fileevent $serial readable [list serial_receiver $serial]
proc serial_receiver { chan } {
if { [eof $chan] } {
puts stderr "Closing $chan"
catch {close $chan}
return
}
set data [read $chan]
set size [string length $data]
puts "received $size bytes: $data"
}
(disclaimer: this is taken verbatim from here)
EDIT: I am sorry but I do not have enough reputation to comment, but it is probably a good idea to specify the platform to narrow down what the permission issues might be related to.