From 34e43c7ee9700249dc6e5b333b7c264d45d6b530 Mon Sep 17 00:00:00 2001
From: Damien George <damien.p.george@gmail.com>
Date: Mon, 25 Aug 2014 18:12:44 +0100
Subject: [PATCH] stmhal: Improve efficiency of SysTick IRQ and HAL_Delay.
SysTick IRQ now increases millisecond counter directly (ie without
calling HAL_IncTick). Provide our own version of HAL_Delay that does a
wfi while waiting. This more than halves power consumption when running
a loop containing a pyb.delay call. It used to be like this, but new
version of HAL library regressed this feature.
---
stmhal/hal/src/stm32f4xx_hal.c | 2 +-
stmhal/stm32f4xx_it.c | 6 +++++-
stmhal/systick.c | 12 ++++++++++++
3 files changed, 18 insertions(+), 2 deletions(-)
diff --git a/stmhal/hal/src/stm32f4xx_hal.c b/stmhal/hal/src/stm32f4xx_hal.c
index 6c076c358..0040658a0 100644
--- a/stmhal/hal/src/stm32f4xx_hal.c
+++ b/stmhal/hal/src/stm32f4xx_hal.c
@@ -93,7 +93,7 @@
#define CMPCR_CMP_PD_BB (PERIPH_BB_BASE + (CMPCR_OFFSET * 32) + (CMP_PD_BitNumber * 4))
/* Private macro -------------------------------------------------------------*/
/* Private variables ---------------------------------------------------------*/
-static __IO uint32_t uwTick;
+__IO uint32_t uwTick;
/* Private function prototypes -----------------------------------------------*/
/* Private functions ---------------------------------------------------------*/
diff --git a/stmhal/stm32f4xx_it.c b/stmhal/stm32f4xx_it.c
index 4bd13c05c..74fdf53d1 100644
--- a/stmhal/stm32f4xx_it.c
+++ b/stmhal/stm32f4xx_it.c
@@ -173,7 +173,11 @@ void PendSV_Handler(void) {
* @retval None
*/
void SysTick_Handler(void) {
- HAL_IncTick();
+ // Instead of calling HAL_IncTick we do the increment here of the counter.
+ // This is purely for efficiency, since SysTick is called 1000 times per
+ // second at the highest interrupt priority.
+ extern __IO uint32_t uwTick;
+ uwTick += 1;
// Read the systick control regster. This has the side effect of clearing
// the COUNTFLAG bit, which makes the logic in sys_tick_get_microseconds
diff --git a/stmhal/systick.c b/stmhal/systick.c
index b2381d08e..b4dd68ffe 100644
--- a/stmhal/systick.c
+++ b/stmhal/systick.c
@@ -33,6 +33,18 @@
#include "irq.h"
#include "systick.h"
+// We provide our own version of HAL_Delay that calls __WFI while waiting, in
+// order to reduce power consumption.
+void HAL_Delay(uint32_t Delay) {
+ extern __IO uint32_t uwTick;
+ uint32_t start = uwTick;
+ // Wraparound of tick is taken care of by 2's complement arithmetic.
+ while (uwTick - start < Delay) {
+ // Enter sleep mode, waiting for (at least) the SysTick interrupt.
+ __WFI();
+ }
+}
+
bool sys_tick_has_passed(uint32_t start_tick, uint32_t delay_ms) {
return HAL_GetTick() - start_tick >= delay_ms;
}
--
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