atrf-path: added min/max values and corrected averaging algorithm

- atrf-path.c (rssi_to_dBm, sample): moved RSSI value to dBm conversion to
  separate function
- atrf-path.c (sample): corrected calculation of average
- atrf-path.c (sample): also output minimum and maximum value
- plot: new option -e to display extremal values
- plot: added comment to explain y range

tools/atrf-path/atrf-path.c

@@ -50,10 +50,17 @@ static void init_rx(struct atrf_dsc *dsc, int trim, int chan)
 }
 
 
+static double rssi_to_dBm(double rssi)
+{
+	return -91+3*(rssi-1);
+}
+
+
 static void sample(struct atrf_dsc *tx, struct atrf_dsc *rx, int trim_tx,
     int power, int chan, int cont_tx, int samples)
 {
-	int i, rssi = 0;
+	int i, rssi;
+	int sum = 0, min = -1, max = -1;
 	double offset = tx_power_step2dBm(tx, power);
 
 	init_tx(tx, trim_tx, power, chan);
@@ -67,14 +74,20 @@ static void sample(struct atrf_dsc *tx, struct atrf_dsc *rx, int trim_tx,
 		/* according to 8.3.2, PHY_RSSI is updated every 2 us */
 		usleep(2);
 
-		rssi += atrf_reg_read(rx, REG_PHY_RSSI) & RSSI_MASK;
+		rssi = atrf_reg_read(rx, REG_PHY_RSSI) & RSSI_MASK;
+		sum += rssi;
+		if (min == -1 || rssi < min)
+			min = rssi;
+		if (rssi > max)
+			max = rssi;
 	}
 
 	cw_test_end(tx);
 
-	printf("%.1f %.1f\n",
+	printf("%.1f %.2f %.0f %.0f\n",
 	    2350+5*chan+(cont_tx == CONT_TX_M500K ? -0.5 : 0.5),
-	    -91+3*(rssi-1.0)/samples-offset);
+	    rssi_to_dBm((double) sum/samples)-offset,
+	    rssi_to_dBm(min)-offset, rssi_to_dBm(max)-offset);
 }
 
 

tools/atrf-path/plot

@@ -2,11 +2,18 @@
 
 usage()
 {
-	echo "usage: file ..." 1>&2
+	echo "usage: [-e] file ..." 1>&2
 	exit 1
 }
 
+style=lines
+if [ "$1" = -e ]; then
+	style=errorlines
+	shift
+fi
+
 [ "$1" ] || usage
+
 files=
 while [ "$1" ]; do
 	[ "$files" ] && files="$files, "
@@ -15,9 +22,12 @@ while [ "$1" ]; do
 done
 
 gnuplot -persist <<EOF
+# the y range is not entirely correct - we have RSSI in [-94, -10], and 
+# TX in [-17, 3], so the theoretically possible range would be [-97, 7].
 set yrange [-94:-10]
 set ylabel "RX-TX power (dBm)"
 set xlabel "Frequency (MHz)"
-set style data lines
+set bars small
+set style data $style
 plot $files
 EOF