Add TIMER0 based ticker for OS

os/hal/ports/NRF51/NRF51822/st_lld.c

@@ -50,6 +50,29 @@
 /* Driver interrupt handlers.                                                */
 /*===========================================================================*/
 
+#if (OSAL_ST_MODE == OSAL_ST_MODE_PERIODIC) || defined(__DOXYGEN__)
+/**
+ * @brief   System Timer vector.
+ * @details This interrupt is used for system tick in periodic mode.
+ *
+ * @isr
+ */
+OSAL_IRQ_HANDLER(Vector60) {
+
+  OSAL_IRQ_PROLOGUE();
+
+  /* Clear timer compare event */
+  if (NRF_TIMER0->EVENTS_COMPARE[0] != 0)
+    NRF_TIMER0->EVENTS_COMPARE[0] = 0;
+
+  osalSysLockFromISR();
+  osalOsTimerHandlerI();
+  osalSysUnlockFromISR();
+
+  OSAL_IRQ_EPILOGUE();
+}
+#endif /* OSAL_ST_MODE == OSAL_ST_MODE_PERIODIC */
+
 /*===========================================================================*/
 /* Driver exported functions.                                                */
 /*===========================================================================*/
@@ -60,6 +83,31 @@
  * @notapi
  */
 void st_lld_init(void) {
+
+#if OSAL_ST_MODE == OSAL_ST_MODE_PERIODIC
+  NRF_TIMER0->TASKS_CLEAR = 1;
+
+  /*
+   * Using 32-bit mode with prescaler 16 configures this
+   * timer with a 1MHz clock.
+   */
+  NRF_TIMER0->BITMODE = 3;
+  NRF_TIMER0->PRESCALER = 4;
+
+  /*
+   * Configure timer 0 compare capture 0 to generate interrupt
+   * and clear timer value when event is generated.
+   */
+  NRF_TIMER0->CC[0] = (1000000 / OSAL_ST_FREQUENCY) - 1;
+  NRF_TIMER0->SHORTS = 1;
+  NRF_TIMER0->INTENSET = 0x10000;
+
+  nvicEnableVector(TIMER0_IRQn, 8);
+
+  /* Start timer */
+  NRF_TIMER0->TASKS_START = 1;
+#endif
+
 }
 
 #endif /* OSAL_ST_MODE != OSAL_ST_MODE_NONE */