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--- courses:be2m37mam:tasks:task03 [2019/10/03 10:29]
viteks created
+++ courses:be2m37mam:tasks:task03 [2019/11/14 13:47]
viteks [How timer / counter works]
@@ Line 1: / Line 1: @@
 ====== T03 - Stopwatch ======
+Write a program for [[courses:be2m37mam:hardware:nucleo|Nucleo STM32F401RE]] and [[courses:be2m37mam:hardware:shield|Experimental shield]], that performs a 1s precision stopwatch (or better).
+===== Instructions: =====
+  * Use LED display on the Experimental shield
+  * Use button S1 to start/stop/clear stopwatch
+==== How timer / counter works ====
+{{ :courses:be2m37mam:tasks:timer-1.svg |}}
+==== Timer TIM2 (pooling) ====
+<code c>
+fine getbit(reg, bit)      (((reg) & (1U << (bit))) >> (bit))
+void initLED(void) {
+    setbit(RCC->AHB1ENR, 0);
+    setbit(GPIOA->MODER, 10);
+}
+void initTIM2(void)
+{
+    /*
+     * TIM2 je pripojen ke sbernici APB1, ktera bezi na 16MHz
+     * frekvence pred TIM2 je zvojnasobena PLL
+     */
+    setbit(RCC->APB1ENR, 0);  /* enable Clock for TIM2 */
+    TIM2->PSC = ?;                /* prescaler - doplnte podle potreby */
+    TIM2->ARR = ?;                /* autoreload - doplnte podle potreby */
+    setbit(TIM2->CR1, 0);        /* enable TIM2 */
+    clearbit(TIM2->SR, 0);       /* status TIM2 */
+}
+int main(void)
+{
+    initLED();
+    initTIM2();
+    while(1)
+    {
+        /* test na UEV (update event)    */
+        if(getbit(TIM2->SR, 0))
+        {
+            togglebit(GPIOA->ODR, 5);
+            /* vraceni status bitu na log 0 */
+            clearbit(TIM2->SR, 0);
+        }
+    }
+}
+</code>