Something

proc sendCommand {rig command} {
	puts -nonewline $rig "$command\r"
	flush $rig
}

proc readResult {rig} {
	set result ""
	
	while {1} {
		set ch [read $rig 1]
		if {$ch == "\n"} {
			break
		}
		set result "$result$ch"
	}
	
	return $result
}
proc getFrequency {rig vfo} {
	global VFO_B
	
	set vfo "A"
	if {$vfo == $VFO_B} {
		set vfo "B"
	}
	
	sendCommand $rig "?$vfo"
	set hexFreq [readResult $rig]
	puts [string length $hexFreq]
	#binary scan $hexFreq @1I freq
	#return $freq
	
	# Debugging
	binary scan $hexFreq c* data
	foreach byte $data {
   	puts [expr {$byte & 0xff}]
	}
	return "0"
}

set rig [open "/dev/tty.KeySerial1" r+]
fconfigure $rig -mode "57600,n,8,1" -buffering none

set freq [getFrequency $rig $VFO_A]
puts $freq

close $rig