Merge pull request #92 from cnlohr/proposed_update_to_systick

Update systick examples to reflect new sysclk usage.

examples/systick_irq/Makefile

@@ -2,8 +2,6 @@ all : flash
 
 TARGET:=systick_irq
 
-CFLAGS+=-DSTDOUT_UART
-
 include ../../ch32v003fun/ch32v003fun.mk
 
 flash : cv_flash

examples/systick_irq/systick_irq.c

 /*
  * Example for using SysTick with IRQs
  * 03-25-2023 E. Brombaugh
+ * 05-12-2023 C. Lohr (Modified to reflect updated sysclk)
  */
 
 // Could be defined here, or in the processor defines.
 #define SYSTEM_CORE_CLOCK 48000000
+#define SYSTICK_USE_HCLK
 #define APB_CLOCK SYSTEM_CORE_CLOCK
 
 #include "ch32v003fun.h"
@@ -31,19 +33,16 @@ void systick_init(void)
 	/* enable the SysTick IRQ */
 	NVIC_EnableIRQ(SysTicK_IRQn);
 	
-	/* Clear any existing IRQ */
-    SysTick->SR &= ~SYSTICK_SR_CNTIF;
-	
 	/* Set the tick interval to 1ms for normal op */
-    SysTick->CMP = (SYSTEM_CORE_CLOCK/1000)-1;
+	SysTick->CMP = (SYSTEM_CORE_CLOCK/1000)-1;
 	
 	/* Start at zero */
-    SysTick->CNT = 0;
+	SysTick->CNT = 0;
 	systick_cnt = 0;
 	
-	/* Enable SysTick counter, IRQ, HCLK/1, auto reload */
-    SysTick->CTLR = SYSTICK_CTLR_STE | SYSTICK_CTLR_STIE | 
-					SYSTICK_CTLR_STCLK | SYSTICK_CTLR_STRE;
+	/* Enable SysTick counter, IRQ, HCLK/1 */
+	SysTick->CTLR = SYSTICK_CTLR_STE | SYSTICK_CTLR_STIE |
+					SYSTICK_CTLR_STCLK;
 }
 
 /*
@@ -53,25 +52,19 @@ void systick_init(void)
 void SysTick_Handler(void) __attribute__((interrupt));
 void SysTick_Handler(void)
 {
+	// move the compare further ahead in time.
+	// as a warning, if more than this length of time
+	// passes before triggering, you may miss your
+	// interrupt.
+	SysTick->CMP += (SYSTEM_CORE_CLOCK/1000);
+
 	/* clear IRQ */
-    SysTick->SR &= 0;
-	
+	SysTick->SR = 0;
+
 	/* update counter */
 	systick_cnt++;
 }
 
-/*
- * Millisecond delay routine
- */
-void systick_delay_ms(uint32_t milliseconds)
-{
-	/* compute end time */
-	uint32_t etime = systick_cnt + milliseconds;
-	
-	/* wait for current time == end time */
-	while(systick_cnt != etime);
-}
-
 /*
  * entry
  */
@@ -81,8 +74,7 @@ int main()
 	
 	SystemInit48HSI();
 
-	// start serial @ default 115200bps
-	SetupUART( UART_BRR );
+	SetupDebugPrintf();
 	printf("\r\r\n\nsystick_irq example\n\r");
 
 	// init systick @ 1ms rate
@@ -109,13 +101,13 @@ int main()
 	while(1)
 	{
 		GPIOD->BSHR = 1 | (1<<4);	 // Turn on GPIOs
-		systick_delay_ms( 250 );
+		Delay_Ms( 250 );
 		GPIOC->BSHR = 1;
-		systick_delay_ms( 250 );
+		Delay_Ms( 250 );
 		GPIOD->BSHR = (1<<16) | (1<<(16+4)); // Turn off GPIODs
-		systick_delay_ms( 250 );
+		Delay_Ms( 250 );
 		GPIOC->BSHR = (1<<16);
-		systick_delay_ms( 250 );
-		printf( "Count: %lu\n\r", count++ );
+		Delay_Ms( 250 );
+		printf( "Print #: %lu / Milliseconds: %lu / CNT: %lu\n\r", count++, systick_cnt, SysTick->CNT );
 	}
 }