Serial Port behavior in tcl

From: Andy McAllister (drsmartz_at_yahoo.com)
Date: 11/24/04 

Date: 24 Nov 2004 11:08:39 -0800

I have an application which is very simple - I have created a
peripheral sensor which outputs +7VDC on the RX pin on a laptop with
tcl/tk 8.4.7. When the sensor detects a magnet (from a model train) it
puts 0 VDC on the RX pin. I want to make a tcl app on the laptop that
counts the number of times the sensor senses a magnet.

I have 3 machines loaded with tcl 8.4.7. The sensor and my app works
fine on both of these:
- a Dell Latitude P3 laptop in Win2K
- a P4 Panasonic laptop running redhat 8.0
But my P133 Sharp laptop running Redhat 5.2 doesn't work with the
sensor.

Using the "term.tcl" application (code pasted below) I can test the
port - I just connect pins 2 and 3 together to make a loopback. I can
type and see my typing on screen, so I know the serial port works on
the Sharp laptop. One thing I noticed, it does not work at 9600 baud,
but does loopback chracters at 19600, 2400, and 1200 baud. So I know
the port works and that /dev/ttyS0 is correct, and I know the sensor
works to trigger fileevent on the other machines. But the sensor does
not trigger a fileevent on the Sharp laptop like it does the Dell and
Panasonic laptops. I put a bell into the receive subroutine, but never
get a bell when I have the sensor plugged in and triggering on the
Sharp laptop.

Note that using the term.tcl program on the Panasonic laptop causes a
symbol "x/00" to print on the terminal. I don't care what symbol is
sent, just so I get SOMEthing in the laptop's RX serial buffer to
trigger fileevent which will increment the counter. I have a timer in
my code (included below as the file train.tcl, largely based on
term.tcl) to assure only one trigger can happen in so many seconds.

I know this is crude, but I wanted to keep it simple...

If anyone has some insight, I'd greatly appreciate it.

## term.tcl:
###############################################################################
# Term for a simple terminal interface

###############################################################################
# The terminal bindings are implemented by defining a new bindtag
'Term'

###############################################################################

# Configure your serial port here
#
set Term(Port) com1
set Term(Mode) "19200,n,8,1"
set Term(Font) Courier

# Global variables
#
set Term(Text) {}

##################### Terminal In/Out events
############################
proc term_out { chan key } {
switch -regexp -- $key {
[\x07-\x08] -
\x0D -
[\x20-\x7E] { puts -nonewline $chan $key; return -code break }
[\x01-\x06] -
[\x09-\x0C] -
[\x0E-\x1F] -
\x7F { return }
default { return }
} ;# switch
}

proc term_in { ch } {
upvar #0 Term(Text) txt

switch -regexp -- $ch {
\x07 { bell }
\x0A { # ignore }
\x0D { $txt insert end "\n" }
default { $txt insert end $ch }
}
$txt see end
}

proc receiver {chan} {
foreach ch [ split [read $chan] {}] {
term_in $ch
}
}

##################### Windows ############################
proc scrolled_text { f args } {
frame $f
eval {text $f.text \
-xscrollcommand [list $f.xscroll set] \
-yscrollcommand [list $f.yscroll set]} $args
scrollbar $f.xscroll -orient horizontal \
-command [list $f.text xview]
scrollbar $f.yscroll -orient vertical \
-command [list $f.text yview]
grid $f.text $f.yscroll -sticky news
grid $f.xscroll -sticky news
grid rowconfigure $f 0 -weight 1
grid columnconfigure $f 0 -weight 1
return $f.text
}

##### main #######

set chan [open $Term(Port) r+]
fconfigure $chan -mode $Term(Mode) -translation binary -buffering none
-blocking 0
fileevent $chan readable [list receiver $chan]

set Term(Text) [scrolled_text .t -width 80 -height 25 -font
$Term(Font) ]
pack .t -side top -fill both -expand true

bind $Term(Text) <Any-Key> [list term_out $chan %A]

catch {console hide}

##Train.tcl
###############################################################################
# Train for BagelME!

###############################################################################
# The terminal bindings are implemented by defining a new bindtag
'Term'

###############################################################################

# Configure your serial port here
#
set Term(Port) /dev/ttyS0
set Term(Mode) "2400,n,8,1"
set dist 0
set trackdist 0.1
# this is in inches for distance around the track
set hysteresis 1.5
# this var is in seconds to wait between signals on the sensor
set lasttime [clock seconds]

# Global variables
#
set Term(Text) {}

##################### Terminal In/Out events
############################

proc term_in {} {
global dist trackdist

set dist [expr $dist + $trackdist]

.count config -text $dist
}

proc receiver {chan} {
global lasttime hysteresis
if { [catch { gets $chan } fid] } {
puts stdout "Serial got messed up: $fid"
}

if {[expr $lasttime + $hysteresis] < [clock seconds]} {

term_in
set lasttime [clock seconds]
} else {

}

}

##################### Windows ############################

button .quit -text Quit -command exit
set fonttype [font create Arial]
font configure $fonttype -size 400
label .count -text $dist -font $fonttype
pack .quit .count -side bottom

##### main #######

set chan [open $Term(Port) r+]
fconfigure $chan -mode $Term(Mode) -translation binary -buffering none
-blocking 0
fileevent $chan readable [list receiver $chan]

catch {console hide}