From 497f20dfffe5ebfb8c74ddfd90f478184e23d29d Mon Sep 17 00:00:00 2001
From: Michael Wiebusch <stratomaster@gmx.net>
Date: Wed, 17 Jul 2013 14:30:58 +0200
Subject: [PATCH] more comfortable serial polling loop in GW instek power
 supply remote control

---
 web/htdocs/tools/pwr/pwr.pl | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/web/htdocs/tools/pwr/pwr.pl b/web/htdocs/tools/pwr/pwr.pl
index 3699b57..bf13e3e 100755
--- a/web/htdocs/tools/pwr/pwr.pl
+++ b/web/htdocs/tools/pwr/pwr.pl
@@ -99,11 +99,12 @@ sub receive_answer {
 	# clear buffers, then send the "list"-command to the power supply
 	$port->lookclear; 
 	$port->write("L\r");
-	# sleep a second to give the supply time to react
-	usleep 1E5;
 
-	# read what has accumulated in the serial buffer
-	while(my $a = $port->lookfor) {
+
+  # do polling for 5 seconds, break polling as soon as answer was received
+  my $i;
+  for ($i = 0; ($i<500) ;$i++) {
+    my $a = $port->lookfor;
 		#print $a."\n"; # debug output
 		if ($a =~ m/V(\d\d\.\d\d)A(\d\.\d\d\d)W(\d\d\d\.\d)U(\d\d)I(\d\.\d\d)P(\d\d\d)F(\d\d\d\d\d\d)/) {
 			$found = 1;
@@ -145,9 +146,11 @@ sub receive_answer {
 			
 			last;
 	
+		} else {
+      usleep 1E4; # 10 ms delay
 		}
 	}
-	}
+}
 
 sub receive_answer_HMP {
   my $ret ="";
-- 
2.43.0