Diff: targets/hal/TARGET_STM/TARGET_STM32F0/us_ticker.c

Revision:

140:6f18478c63fa

Parent:

0:9b334a45a8ff

Child:

144:ef7eb2e8f9f7

--- a/targets/hal/TARGET_STM/TARGET_STM32F0/us_ticker.c	Mon May 23 16:00:17 2016 +0100
+++ b/targets/hal/TARGET_STM/TARGET_STM32F0/us_ticker.c	Tue May 24 11:30:12 2016 +0100
@@ -41,6 +41,7 @@
 volatile uint32_t SlaveCounter = 0;
 volatile uint32_t oc_int_part = 0;
 volatile uint16_t oc_rem_part = 0;
+volatile uint16_t cnt_val = 0;
 
 void set_compare(uint16_t count) {
     TimMasterHandle.Instance = TIM_MST;
@@ -58,24 +59,15 @@
 }
 
 uint32_t us_ticker_read() {
-    uint32_t counter, counter2;
+    uint32_t counter;
     if (!us_ticker_inited) us_ticker_init();
-    // A situation might appear when Master overflows right after Slave is read and before the
-    // new (overflowed) value of Master is read. Which would make the code below consider the
-    // previous (incorrect) value of Slave and the new value of Master, which would return a
-    // value in the past. Avoid this by computing consecutive values of the timer until they
-    // are properly ordered.
+
+    //Current value of TIM_MST->CNT is stored in cnt_val and is
+    //updated in interrupt context
     counter = (uint32_t)(SlaveCounter << 16);
-    counter += TIM_MST->CNT;
-    while (1) {
-        counter2 = (uint32_t)(SlaveCounter << 16);
-        counter2 += TIM_MST->CNT;
-        if (counter2 > counter) {
-            break;
-        }
-        counter = counter2;
-    }
-    return counter2;
+    counter += cnt_val;
+
+    return counter;
 }
 
 void us_ticker_set_interrupt(timestamp_t timestamp) {