by [Theo Verelst]

This pagevis about two essential tcl scripts for a big project of mine, whichvis a computer and otherwise controlled audio mixer.

[http://82.170.247.158/Wiki/dsc00194b.jpg]
The prototype hardware in buildup

Both the control side in the mixer machine and the control program on a PC are pure [Tcl], which is fun and well maintainable.

The prototype with its tcl-scripts currently controls (in very high quality) one stereo volume via a slider on the screen of a Linux (I used Fedora Core 6/64) or Windows XP (professional):

[http://82.170.247.158/Wiki/scrvol1.jpg]

The first tryout script is this one:

 proc slidsend { {n} {v} } {
  set w [format "%.2x" [expr $v+191]]
  send "00$w$w$w"

 }

 proc slidsendupdate { } {

 #   send update

 } 


 
 set sock {}
 proc send { {line {\n}} } {
   global sock
   if {$sock == -1} {
     # log "(failed attempt to send:\n$line)\n"
      return
   }
   puts $sock $line
   flush $sock
   # log $line\n
 } 

 proc log a {puts -nonewline $a}


 
 set sock [socket 192.168.1.38 4448]

 #sliders {{vol 255}}

 
 
 wm geometry . 88x478
 scale .sl
 .sl conf -from 64 -to -191 -tickinterval 32 -command {slidsend 0 }
 pack .sl -expand y -fill y

The slider above is shown on the screen, moving it immedeately changes the volume of the single text channel of the mixer.

The ticks are in 0.5 dB steps ( a small volume change), which is not to lose resolution, when the slider values would be in Decibels, (-96 .. 31.5) the accuracy would become a decibel per slider step.

The send command computes the hardware setting and assumes exactly 4 bytes must be send over the socket per volume change. The local IP address is of the mixer machine.


[http://82.170.247.158/Wiki/volume1.jpg]



 set sock [socket -server connect 4448]
 set s1 {}

 proc connect {s host port} {
    global s1
    set s1 $s
    fconfigure $s1 -blocking 0 -buffering line
    fileevent $s1 readable [list handleSocket $s1]
 }

 proc handleSocket {s} {
    gets $s line
    if {[eof $s]} {
        close $s
        set s -1
        return
    }
    if {$line eq ""} return
    w $line
 }


 set fh [open /dev/ttyS2 RDWR]
 
 fconfigure $fh -blocking 0 -mode 115200,n,8,1 -translation binary \
    -buffering  full
 
 fileevent $fh readable {
    set w [read $fh] ;
    foreach c [split $w {}] {
       binary scan $c H* a; set v $a
       if {$s1 != {}} {puts $s1 "$v"}
       # flush stdout
    }
 }
 proc w h {
    global fh
    puts -nonewline $fh [binary format H* "$h"] ; flush $fh
 }
 w 00 ; w C0 ; w C0 ; w C0
 # after 500 exit
 vwait forever