From 9db719bb57626d72ab84ab0ccd2294bf89158762 Mon Sep 17 00:00:00 2001
From: Dave Hylands
Date: Thu, 13 Mar 2014 15:40:34 -0700
Subject: stmhal - More systick cleanup. Fix HAL_Delay

---
 stmhal/hal/src/stm32f4xx_hal.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

(limited to 'stmhal/hal/src')

diff --git a/stmhal/hal/src/stm32f4xx_hal.c b/stmhal/hal/src/stm32f4xx_hal.c
index 6df59f9f9..672422553 100644
--- a/stmhal/hal/src/stm32f4xx_hal.c
+++ b/stmhal/hal/src/stm32f4xx_hal.c
@@ -281,11 +281,13 @@ uint32_t HAL_GetTick(void)
   */
 void HAL_Delay(__IO uint32_t Delay)
 {
-  uint32_t timingdelay;
-  
-  timingdelay = HAL_GetTick() + Delay;
-  while(HAL_GetTick() < timingdelay)
-  {
+  uint32_t start = HAL_GetTick();
+
+  // Note that the following works (due to the magic of 2's complement numbers)
+  // even when Delay causes wraparound.
+
+  while (HAL_GetTick() - start <= Delay) {
+    __WFI();  // enter sleep mode, waiting for interrupt
   }
 }
 
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