From d85fd461d9a17811f8d0d8fa11fcebf7fa542ee4 Mon Sep 17 00:00:00 2001
From: Cobus van Eeden <35851496+cobusve@users.noreply.github.com>
Date: Thu, 27 Aug 2020 10:12:51 -0700
Subject: [PATCH] Fix inaccurate ticks in windows port (#142)

---
 portable/MSVC-MingW/port.c | 40 +++++++++++++++++++++++++-------------
 1 file changed, 26 insertions(+), 14 deletions(-)

diff --git a/portable/MSVC-MingW/port.c b/portable/MSVC-MingW/port.c
index f5e26a98d..81b5f3466 100644
--- a/portable/MSVC-MingW/port.c
+++ b/portable/MSVC-MingW/port.c
@@ -22,7 +22,6 @@
  * https://www.FreeRTOS.org
  * https://github.com/FreeRTOS
  *
- * 1 tab == 4 spaces!
  */
 
 /* Standard includes. */
@@ -140,6 +139,9 @@ static DWORD WINAPI prvSimulatedPeripheralTimer( LPVOID lpParameter )
 {
 TickType_t xMinimumWindowsBlockTime;
 TIMECAPS xTimeCaps;
+TickType_t xWaitTimeBetweenTicks = portTICK_PERIOD_MS;
+HANDLE hTimer = NULL;
+LARGE_INTEGER liDueTime;
 
 	/* Set the timer resolution to the maximum possible. */
 	if( timeGetDevCaps( &xTimeCaps, sizeof( xTimeCaps ) ) == MMSYSERR_NOERROR )
@@ -159,22 +161,32 @@ TIMECAPS xTimeCaps;
 	/* Just to prevent compiler warnings. */
 	( void ) lpParameter;
 
+	/* Tick time for the timer is adjusted with the maximum available
+	 resolution. */
+	if( portTICK_PERIOD_MS < xMinimumWindowsBlockTime )
+	{
+		xWaitTimeBetweenTicks = xMinimumWindowsBlockTime;
+	}
+
+	/* Convert the tick time in milliseconds to nanoseconds resolution
+	 for the Waitable Timer. */
+	liDueTime.u.LowPart = xWaitTimeBetweenTicks * 1000 * 1000;
+	liDueTime.u.HighPart = 0;
+
+	/* Create a synchronization Waitable Timer.*/
+	hTimer = CreateWaitableTimer( NULL, FALSE, NULL );
+
+	configASSERT( hTimer != NULL );
+
+	/* Set the Waitable Timer. The timer is set to run periodically at every
+	xWaitTimeBetweenTicks milliseconds. */
+	configASSERT( SetWaitableTimer( hTimer, &liDueTime, xWaitTimeBetweenTicks, NULL, NULL, 0 ) );
+
 	for( ;; )
 	{
 		/* Wait until the timer expires and we can access the simulated interrupt
-		variables.  *NOTE* this is not a 'real time' way of generating tick
-		events as the next wake time should be relative to the previous wake
-		time, not the time that Sleep() is called.  It is done this way to
-		prevent overruns in this very non real time simulated/emulated
-		environment. */
-		if( portTICK_PERIOD_MS < xMinimumWindowsBlockTime )
-		{
-			Sleep( xMinimumWindowsBlockTime );
-		}
-		else
-		{
-			Sleep( portTICK_PERIOD_MS );
-		}
+		variables. */
+		WaitForSingleObject( hTimer, INFINITE );
 
 		configASSERT( xPortRunning );