Update with an exti example.

examples/exti_pin_change_isr/Makefile

+all : flash
+
+TARGET:=exti_pin_change_isr
+
+test : flash
+	../../minichlink/minichlink -X ECLK 1:0:0:1:63
+
+include ../../ch32v003fun/ch32v003fun.mk
+
+flash : cv_flash
+clean : cv_clean
+
+

examples/exti_pin_change_isr/exti_pin_change_isr.c

+// Could be defined here, or in the processor defines.
+#define SYSTEM_CORE_CLOCK 48000000
+
+#include "ch32v003fun.h"
+#include <stdio.h>
+
+#define APB_CLOCK SYSTEM_CORE_CLOCK
+
+volatile uint32_t count;
+
+// This code uses fast interrupts, but be warned, in this mode your hardware stack 
+// is only 2 interrupt calls deep!!!
+//
+// When you execute code here, from RAM, the latency is between 310 and 480ns.
+// From RAM is using  __attribute__((section(".srodata")));
+// Flash starts at 340ns but seems about the same otherwise, bar the fact it prevents
+// any other apps from running.
+void EXTI7_0_IRQHandler( void ) __attribute__((naked));
+void EXTI7_0_IRQHandler( void ) 
+{
+	// Flash just a little blip.
+	GPIOC->BSHR = 2;
+	GPIOC->BSHR = (2<<16);
+
+	// Acknowledge the interrupt
+	EXTI->INTFR = 1<<3;
+
+	// Return out of function.
+	asm volatile( "mret" );
+}
+
+int main()
+{
+	SystemInit48HSI();
+
+	// Enable GPIOs
+	RCC->APB2PCENR = RCC_APB2Periph_GPIOD | RCC_APB2Periph_GPIOC | RCC_APB2Periph_AFIO;
+
+	// GPIO D3 for input pin change.
+	GPIOD->CFGLR =
+		(GPIO_CNF_IN_PUPD)<<(4*1) |  // Keep SWIO enabled.
+		(GPIO_SPEED_IN | GPIO_CNF_IN_PUPD)<<(4*3);  //PD4 = GPIOD IN
+
+	// GPIO C0 Push-Pull (our output) 
+	GPIOC->CFGLR =
+		(GPIO_Speed_10MHz | GPIO_CNF_OUT_PP)<<(4*0) |
+		(GPIO_Speed_10MHz | GPIO_CNF_OUT_PP)<<(4*1);
+
+	// Ugh this is tricky.
+	// This is how we set (INTSYSCR) to enable hardware interrupt nesting
+	// and hardware stack. BUT this means we can only stack intterrupts 2 deep.
+	//
+	// Note: If you don't do this, you will need to set your functions to be
+	// __attribute__((interrupt)) instead of  __attribute__((naked))  with an
+	// mret.
+	asm volatile( "addi t1,x0, 3\ncsrrw x0, 0x804, t1\n" : : :  "t1" );
+
+
+	// Configure the IO as an interrupt.
+	AFIO->EXTICR = 3<<(3*2); //PORTD.3 (3 out front says PORTD, 3 in back says 3)
+	EXTI->INTENR = 1<<3; // Enable EXT3
+	EXTI->RTENR = 1<<3;  // Rising edge trigger
+
+	// enable interrupt
+	NVIC_EnableIRQ( EXTI7_0_IRQn );
+
+	while(1)
+	{
+		// PC1 constantly toggles, but do realy cursed instructons ;)
+		// this is so we have something we can "break" from
+		GPIOC->BSHR = 1;
+		if( ((uint32_t*)count++) )
+			GPIOC->BSHR = (1<<16);
+		if( count == 100 ) count = 0;
+	}
+}
+