From 699bb320735a5fc0d26b196ef75b5387ffa28226 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E6=9D=A8=E8=BF=9E=E9=92=8A?= <ylz0923@foxmail.com>
Date: Mon, 11 Jun 2018 08:59:30 +0800
Subject: [PATCH] [stm32f10x-HAL] add function rt_hw_us_delay
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

实现rt_hw_us_delay函数
---
 bsp/stm32f10x-HAL/drivers/board.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/bsp/stm32f10x-HAL/drivers/board.c b/bsp/stm32f10x-HAL/drivers/board.c
index 12d5b7d80f..61029214c1 100644
--- a/bsp/stm32f10x-HAL/drivers/board.c
+++ b/bsp/stm32f10x-HAL/drivers/board.c
@@ -113,3 +113,23 @@ void rt_hw_board_init(void)
     rt_console_set_device(RT_CONSOLE_DEVICE_NAME);
 #endif
 }
+
+/**
+ * This function will delay for some us.
+ *
+ * @param us the delay time of us
+ */
+void rt_hw_us_delay(rt_uint32_t us)
+{
+    rt_uint32_t delta;
+    us = us * (SysTick->LOAD / (1000000 / RT_TICK_PER_SECOND));
+    delta = SysTick->VAL;
+    if (delta < us)
+    {
+        /* wait current OSTick left time gone */
+        while (SysTick->VAL < us);
+        us -= delta;
+        delta = SysTick->LOAD;
+    }
+    while (delta - SysTick->VAL < us);
+}