Added demo for systick - not working yet.

examples/systick_irq/Makefile

+TARGET:=systick_irq
+
+all : flash
+
+PREFIX:=riscv64-unknown-elf
+
+GPIO_Toggle:=EXAM/GPIO/GPIO_Toggle/User
+
+CH32V003FUN:=../../ch32v003fun
+MINICHLINK:=../../minichlink
+
+CFLAGS:= \
+	-g -Os -flto -ffunction-sections \
+	-static-libgcc -lgcc \
+	-march=rv32ec \
+	-mabi=ilp32e \
+	-I/usr/include/newlib \
+	-I$(CH32V003FUN) \
+	-nostdlib \
+	-I. -DSTDOUT_UART -Wall
+
+LDFLAGS:=-T $(CH32V003FUN)/ch32v003fun.ld -Wl,--gc-sections
+
+SYSTEM_C:=$(CH32V003FUN)/ch32v003fun.c
+
+$(TARGET).elf : $(SYSTEM_C) $(TARGET).c
+	$(PREFIX)-gcc -o $@ $^ $(CFLAGS) $(LDFLAGS)
+
+$(TARGET).bin : $(TARGET).elf
+	$(PREFIX)-size $^
+	$(PREFIX)-objdump -S $^ > $(TARGET).lst
+	$(PREFIX)-objdump -t $^ > $(TARGET).map
+	$(PREFIX)-objcopy -O binary $< $(TARGET).bin
+	$(PREFIX)-objcopy -O ihex $< $(TARGET).hex
+
+flash : $(TARGET).bin
+	$(MINICHLINK)/minichlink -w $< flash -b
+
+clean :
+	rm -rf $(TARGET).elf $(TARGET).bin $(TARGET).hex $(TARGET).lst $(TARGET).map $(TARGET).hex
+

examples/systick_irq/systick.h

+/*
+ * Single-File-Header for using SysTick with millisecond interrupts
+ * 03-25-2023 E. Brombaugh
+ */
+
+#ifndef _SYSTICK_H
+#define _SYSTICK_H
+
+#include <stdint.h>
+
+/* some bit definitions for systick regs */
+#define SYSTICK_SR_CNTIF (1<<0)
+#define SYSTICK_CTLR_STE (1<<0)
+#define SYSTICK_CTLR_STIE (1<<1)
+#define SYSTICK_CTLR_STCLK (1<<2)
+#define SYSTICK_CTLR_STRE (1<<3)
+#define SYSTICK_CTLR_SWIE (1<<31)
+
+volatile uint32_t systick_cnt;
+
+/*
+ * Start up the SysTick IRQ
+ */
+void systick_init(void)
+{
+	/* enable the SysTick IRQ */
+	NVIC_EnableIRQ(SysTicK_IRQn);
+	
+	/* Clear any existing IRQ */
+    SysTick->SR &= ~SYSTICK_SR_CNTIF;
+	
+#if 0
+	/* Set the tick interval to 1ms for normal op */
+    SysTick->CMP = (SYSTEM_CORE_CLOCK/1000)-1;
+#else	
+	/* Set the tick interval to 100ms for debug */
+    SysTick->CMP = (SYSTEM_CORE_CLOCK)-1;
+#endif
+	
+	/* Start at zero */
+    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;
+}
+
+#if 1
+/*
+ * SysTick ISR just counts ticks
+ */
+void SysTick_Handler(void) __attribute__((interrupt("WCH-Interrupt-fast")));
+//void SysTick_Handler(void) __attribute__((interrupt("interrupt")));
+void SysTick_Handler(void)
+{
+	/* clear IRQ */
+    SysTick->SR &= ~SYSTICK_SR_CNTIF;
+	
+	/* update counter */
+	systick_cnt++;
+	
+	printf("systick_cnt = 0x%08X\n\r", systick_cnt);
+
+}
+#endif
+
+/*
+ * 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);
+}
+
+#endif

examples/systick_irq/systick_irq.c

+/*
+ * Example for using SysTick with IRQs
+ * 03-25-2023 E. Brombaugh
+ */
+
+// Could be defined here, or in the processor defines.
+#define SYSTEM_CORE_CLOCK 48000000
+#define APB_CLOCK SYSTEM_CORE_CLOCK
+
+#include "ch32v003fun.h"
+#include <stdio.h>
+#include "systick.h"
+
+int main()
+{
+	uint32_t count = 0;
+	
+	SystemInit48HSI();
+
+	// start serial @ default 115200bps
+	SetupUART( UART_BRR );
+	printf("\r\r\n\nsystick_irq example\n\r");
+
+	printf("SysTick_Handler = 0x%08X\n\r", SysTick_Handler);
+
+	// init systick @ 1ms rate
+	printf("initializing systick...");
+	systick_init();
+	printf("done.\n\r");
+	
+#if 1
+	// Debugging - does ISR run & inc counter?
+	// this section shows that IRQs during print will reset system, but during
+	// inf while() do not.
+	//while(1)
+	//for(int i=0;i<20;i++)
+	//{
+		//printf("i = %d ", i);
+		printf("CNT = 0x%08X ", SysTick->CNT);
+		printf("systick_cnt = 0x%08X\n\r", systick_cnt);
+	//}
+	
+	// does cnt inc?
+	//uint32_t pcnt = systick_cnt;
+	while(1)
+	{
+		//if(pcnt != systick_cnt)
+		//{
+		//	printf("systick_cnt = %d\n\r", systick_cnt);
+		//	pcnt = systick_cnt;
+		//}
+	}
+#else
+	// Testing 1ms Systick
+	// Enable GPIOs
+	RCC->APB2PCENR |= RCC_APB2Periph_GPIOD | RCC_APB2Periph_GPIOC;
+
+	// GPIO D0 Push-Pull
+	GPIOD->CFGLR &= ~(0xf<<(4*0));
+	GPIOD->CFGLR |= (GPIO_Speed_10MHz | GPIO_CNF_OUT_PP)<<(4*0);
+
+	// GPIO D4 Push-Pull
+	GPIOD->CFGLR &= ~(0xf<<(4*4));
+	GPIOD->CFGLR |= (GPIO_Speed_10MHz | GPIO_CNF_OUT_PP)<<(4*4);
+
+	// GPIO C0 Push-Pull
+	GPIOC->CFGLR &= ~(0xf<<(4*0));
+	GPIOC->CFGLR |= (GPIO_Speed_10MHz | GPIO_CNF_OUT_PP)<<(4*0);
+
+	//printf("looping...\n\r");
+	while(1)
+	{
+		GPIOD->BSHR = 1 | (1<<4);	 // Turn on GPIOs
+		GPIOC->BSHR = 1;
+		systick_delay_ms( 250 );
+		GPIOD->BSHR = (1<<16) | (1<<(16+4)); // Turn off GPIODs
+		GPIOC->BSHR = (1<<16);
+		systick_delay_ms( 250 );
+		printf( "Count: %lu\n\r", count++ );
+	}
+#endif
+}