Merge pull request #52 from emeb/master

Updated for SysTick IRQ example for latest changes in ch32v003fun library.

examples/systick_irq/README.md

@@ -4,11 +4,11 @@ interrupts for timing. Many bare-metal and RTOS based embedded applications will
 use the Systick IRQ for timing, periodic housekeeping and task arbitration so
 knowing how to set that up is useful.
 
-Note that this example is *NOT* compatible with the Delay_Ms() function that's
-part of the ch32v003fun library - that function uses the Systick counter for
-doing busy-wait delays and will interfere with its use in generating predictable
-IRQs. Do not use the built-in Delay_Ms() and related functions when using Systick
-for IRQs.
+Note that this example is *NOT* compatible with the Delay_*() functions that are
+part of the ch32v003fun library - those functions use the Systick counter for
+doing busy-wait delays and assume that the CNT register rolls over at 32-bit
+maximum. Do not use the built-in Delay_Ms() and related functions when using
+Systick for IRQs.
 
 Note also the use of the  `__attribute__((interrupt))` syntax in declaring the
 IRQ handler. Some of the IRQ examples from the WCH HAL library have slightly

examples/systick_irq/systick_irq.c

@@ -25,6 +25,9 @@ volatile uint32_t systick_cnt;
  */
 void systick_init(void)
 {
+	/* disable default SysTick behavior */
+	SysTick->CTLR = 0;
+	
 	/* enable the SysTick IRQ */
 	NVIC_EnableIRQ(SysTicK_IRQn);