Timer 16bit: Remove volatile variables. This solved many fails with MBED_24 test.

Author: bcostm

targets/TARGET_STM/us_ticker_16b.c

@@ -67,10 +67,8 @@ uint32_t us_ticker_read() {
 
     if (!us_ticker_inited) us_ticker_init();
 
-    tim_it_update = 0; // Clear TIM_IT_UPDATE event flag
-
 #if defined(TARGET_STM32L0)
-    volatile uint16_t cntH_old, cntH, cntL;
+    uint16_t cntH_old, cntH, cntL;
     do {
         // For some reason on L0xx series we need to read and clear the 
         // overflow flag which give extra time to propelry handle possible
@@ -83,25 +81,23 @@ uint32_t us_ticker_read() {
             cntH_old += 1;
         }
         cntL = TIM_MST->CNT;
-
         cntH = SlaveCounter;
         if (__HAL_TIM_GET_FLAG(&TimMasterHandle, TIM_FLAG_UPDATE) == SET) {
             cntH += 1;
         }
     } while(cntH_old != cntH);
-    
     // Glue the upper and lower part together to get a 32 bit timer
-    counter = (uint32_t)(cntH << 16 | cntL);
+    return (uint32_t)(cntH << 16 | cntL);
 #else
+    tim_it_update = 0; // Clear TIM_IT_UPDATE event flag
     counter = TIM_MST->CNT + (uint32_t)(SlaveCounter << 16); // Calculate new time stamp
-#endif
-
     if (tim_it_update == 1) {
         return tim_it_counter; // In case of TIM_IT_UPDATE return the time stamp that was calculated in timer_irq_handler()
     }
     else {
         return counter; // Otherwise return the time stamp calculated here
     }
+#endif
 }
 
 void us_ticker_set_interrupt(timestamp_t timestamp) {