HAL_GetTick returns elapsed time

Author: bcostm

targets/TARGET_STM/hal_tick_16b.c

@@ -19,6 +19,8 @@
 #if TIM_MST_16BIT
 
 extern TIM_HandleTypeDef TimMasterHandle;
+extern uint32_t prev_time;
+extern uint32_t elapsed_time;
 
 volatile uint32_t PreviousVal = 0;
 
@@ -108,6 +110,10 @@ HAL_StatusTypeDef HAL_InitTick(uint32_t TickPriority)
     TIM_MST_DBGMCU_FREEZE;
 #endif
 
+    // Used by HAL_GetTick()
+    prev_time = 0;
+    elapsed_time = 0;
+
     return HAL_OK;
 }
 

targets/TARGET_STM/hal_tick_common.c

@@ -21,14 +21,25 @@
 // The ticker_read_us function must not be called until the mbed_sdk_init is terminated.
 extern int mbed_sdk_inited;
 
+// Variables also reset in HAL_InitTick()
+uint32_t prev_time = 0;
+uint32_t elapsed_time = 0;
+
+// 1 ms tick is required for ST HAL driver
 uint32_t HAL_GetTick()
 {
-    // 1 ms tick is required for ST HAL driver
+    uint32_t new_time;
     if (mbed_sdk_inited) {
-        return (ticker_read_us(get_us_ticker_data()) / 1000);
+        // Apply the latest time recorded just before the sdk is inited
+        new_time = ticker_read_us(get_us_ticker_data()) + prev_time;
+        prev_time = 0; // Use this time only once
+        return (new_time / 1000);
     }
     else {
-        return (us_ticker_read() / 1000);
+        new_time = us_ticker_read();
+        elapsed_time += (new_time - prev_time) & 0xFFFF; // Only use the lower 16 bits
+        prev_time = new_time;
+        return (elapsed_time / 1000);
     }
 }