SDK Development / mbed-src

mbed SDK library sources

Fork of mbed-src by mbed official

Development branch of the mbed library sources. This library is kept in synch with the latest changes from the mbed SDK and it is not guaranteed to work.

If you are looking for a stable and tested release, please import one of the official mbed library releases:

Import librarymbed

The official Mbed 2 C/C++ SDK provides the software platform and libraries to build your applications.

Last commit 20 Feb 2019 by mbed official

Diff: targets/hal/TARGET_STM/TARGET_NUCLEO_F103RB/us_ticker.c

Revision:
54:24d77221bceb
Parent:
52:a51c77007319
Child:
70:c1fbde68b492
--- a/targets/hal/TARGET_STM/TARGET_NUCLEO_F103RB/us_ticker.c	Tue Dec 03 14:00:05 2013 +0000
+++ b/targets/hal/TARGET_STM/TARGET_NUCLEO_F103RB/us_ticker.c	Sat Dec 07 12:45:04 2013 +0000
@@ -33,6 +33,7 @@
   
     // Time base configuration
     // TIM1 is used as "master", "TIM4" as "slave". TIM4 is clocked by TIM1.
+    TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);
     TIM_TimeBaseStructure.TIM_Period = 0xFFFF;
     TIM_TimeBaseStructure.TIM_Prescaler = (uint16_t)(SystemCoreClock / 1000000) - 1; // 1 µs tick
     TIM_TimeBaseStructure.TIM_ClockDivision = 0;
@@ -42,6 +43,7 @@
     TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure);  
 
     // Master timer configuration
+    TIM_OCStructInit(&TIM_OCInitStructure);
     TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Toggle;
     TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
     TIM_OCInitStructure.TIM_Pulse = 0;
@@ -51,7 +53,7 @@
     TIM_SelectOutputTrigger(TIM1, TIM_TRGOSource_Update);
     
     // Slave timer configuration
-    TIM_SelectSlaveMode(TIM4, TIM_SlaveMode_Gated);
+    TIM_SelectSlaveMode(TIM4, TIM_SlaveMode_External1);
     TIM_SelectInputTrigger(TIM4, TIM_TS_ITR0);
   
     // Enable timers
@@ -60,10 +62,21 @@
 }
 
 uint32_t us_ticker_read() {
-    uint32_t counter;
+    uint32_t counter, counter2;
     if (!us_ticker_inited) us_ticker_init();
-    counter = (uint32_t)((uint32_t)TIM_GetCounter(TIM4) << 16) + (uint32_t)TIM_GetCounter(TIM1);
-    return counter;
+    // A situation might appear when TIM1 overflows right after TIM4 is read and before the
+    // new (overflowed) value of TIM1 is read, which would make the code below consider the
+    // previous (incorrect) value of TIM4 and the new value of TIM1, which would return a
+    // value in the past. Avoid this by computing consecutive values of the timer until they
+    // are properly ordered.
+    counter = counter2 = (uint32_t)((uint32_t)TIM_GetCounter(TIM4) << 16) + (uint32_t)TIM_GetCounter(TIM1);
+    while (1) {
+        counter2 = (uint32_t)((uint32_t)TIM_GetCounter(TIM4) << 16) + (uint32_t)TIM_GetCounter(TIM1);
+        if (counter2 > counter)
+            break;
+        counter = counter2;
+    }
+    return counter2;
 }
 
 void us_ticker_set_interrupt(unsigned int timestamp) {