From baf0850690605960bd90ac7f149892905066039b Mon Sep 17 00:00:00 2001
From: FredericG <FredericG>
Date: Sun, 6 Mar 2011 11:50:54 +0000
Subject: [PATCH] OP-336 CPU usage calculation incorrect when armed - no
 measure the time between calculations

git-svn-id: svn://svn.openpilot.org/OpenPilot/trunk@2987 ebee16cc-31ac-478f-84a7-5cbb03baadba
---
 flight/Modules/System/systemmod.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/flight/Modules/System/systemmod.c b/flight/Modules/System/systemmod.c
index 803123bb9..96efd4fb9 100644
--- a/flight/Modules/System/systemmod.c
+++ b/flight/Modules/System/systemmod.c
@@ -255,6 +255,7 @@ static void updateWDGstats()
  */
 static void updateStats()
 {
+	static portTickType lastTickCount = 0;
 	SystemStatsData stats;
 
 	// Get stats and update
@@ -271,8 +272,14 @@ static void updateStats()
 	if (idleCounterClear) {
 		idleCounter = 0;
 	}
-	stats.CPULoad =
-	    100 - (uint8_t) round(100.0 * ((float)idleCounter / (float)(SYSTEM_UPDATE_PERIOD_MS / 1000)) / (float)IDLE_COUNTS_PER_SEC_AT_NO_LOAD);
+
+	portTickType now = xTaskGetTickCount();
+	if (now > lastTickCount) {
+		uint32_t dT = (xTaskGetTickCount() - lastTickCount) * portTICK_RATE_MS;	// in ms
+		stats.CPULoad =
+			100 - (uint8_t) round(100.0 * ((float)idleCounter / ((float)dT / 1000.0)) / (float)IDLE_COUNTS_PER_SEC_AT_NO_LOAD);
+	} //else: TickCount has wrapped, do not calc now
+	lastTickCount = now;
 	idleCounterClear = 1;
 	
 #if defined(PIOS_INCLUDE_ADC) && defined(PIOS_ADC_USE_TEMP_SENSOR)