timer interrupt example

STM32/libraries/BoardExamples/examples/Discovery407VG/HAL/HAL_InterruptTimer3/HAL_InterruptTimer3.ino

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+/*
+ HAL ( Hardware Abstraction Layer )
+
+ Timer 3 used to call an interrupt routine with constant repetion time.
+
+ Example on how access the HAL within the STM32GENERIC Arduino framework.
+
+ Hardware:
+   STM32F4 Discovery
+
+ contributers: michael_l, danieleff, ChrisMicro
+ May 2017 
+
+*/
+
+static TIM_HandleTypeDef s_TimerInstance = 
+{
+  .Instance = TIM3
+};
+
+extern "C" void TIM3_IRQHandler(void) 
+{
+  HAL_TIM_IRQHandler(&s_TimerInstance);
+  digitalWrite(LED_RED, !digitalRead(LED_RED) );
+}
+
+void setup() 
+{
+  Serial.begin(115200); // Serial is whatever you select in the "Serial communication" menu option
+  pinMode(LED_BUILTIN,OUTPUT);
+  pinMode(LED_RED,OUTPUT);
+
+  HAL_NVIC_SetPriority( TIM3_IRQn, 0, 0 );
+  HAL_NVIC_EnableIRQ  ( TIM3_IRQn );
+  
+  s_TimerInstance.Init.Prescaler = 42000 - 1; //APB1 TIM3 has 84MHZ,
+  s_TimerInstance.Init.CounterMode = TIM_COUNTERMODE_UP;
+  s_TimerInstance.Init.Period = 2000 - 1; // prescaler gives 2khz time base
+  s_TimerInstance.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
+  s_TimerInstance.Init.RepetitionCounter = 0;
+
+  __HAL_RCC_TIM3_CLK_ENABLE();
+  
+  HAL_TIM_Base_Init     ( &s_TimerInstance );
+  HAL_TIM_Base_Start_IT ( &s_TimerInstance );
+}
+
+uint32_t prev = 0;
+
+void loop() 
+{
+  if (__HAL_TIM_GET_COUNTER(&s_TimerInstance) == 0) 
+  {
+    uint32_t now = micros();
+    Serial.print  ( "diff=" ); Serial.println( now - prev );
+    Serial.println( now );
+    prev = micros();
+
+    digitalWrite( LED_BUILTIN, !digitalRead(LED_BUILTIN) );
+  }
+}
+
+