prod/: cleaned up atben clock frequency test

- prod/Common (begin), prod/atben: added clock reference file argument
- prod/atben (xtal_ben): use atrf-xtal options -b and -p to determine
  whether the clock frequency is correct

prod/Common

@@ -114,7 +114,7 @@ expect_re()
 begin()
 {
 	if [ -z "$1" ]; then
-		echo "usage: begin profile" 1>&2
+		echo "usage: begin profile [clock-ref]" 1>&2
 		exit 1
 	fi
 	PROFILE=$1
@@ -122,6 +122,13 @@ begin()
 		echo "$PROFILE not found" 1>&2
 		exit 1
 	fi
+	if [ "$2" ]; then
+		CLKREF=$2
+		if ! $LOCAL_EXEC "[ -r $CLKREF ]"; then
+			echo "$CLKREF not found" 1>&2
+			exit 1
+		fi
+	fi
 }
 
 

prod/atben

@@ -13,12 +13,12 @@ gpio_ben()
 xtal_ben()
 {
 	step "Crystal frequency"
-	cmd "$LOCAL_EXEC atrf-xtal -d $LOCAL_DUT 100"
-	expect_re '4350[012]\.'	# @@@ very crude ...
+	cmd "$LOCAL_EXEC atrf-xtal -d $LOCAL_DUT -b \\\`cat $CLKREF\\\` -p 50 100"
+	expect_re ppm	# we catch any problems via the exit code
 }
 
 
-begin ben.profile
+begin ben.profile ben.xtal
 # power ?
 gpio_ben
 identify