Disabled fast interrupt for open source toolchain.

BSP/Startup/startup_ch32v30x_D8.S

@@ -348,7 +348,11 @@ handle_reset:
     csrw 0xbc0, t0
 
     /* Enable nested and hardware stack */
-	li t0, 0x1f
+	/* li t0, 0x1f */ /* For MRS proprietary GCC compilers */
+
+    /* Enable nested interrupt, disable hardware stack */
+    li t0, 0x1e /* Refer to RISC-V4 PFIC manual */
+
 	csrw 0x804, t0
 
     /* Enable floating point and interrupt */

BSP/Startup/startup_ch32v30x_D8C.S

@@ -368,7 +368,11 @@ handle_reset:
     csrw 0xbc0, t0
 
     /* Enable nested and hardware stack */
-	li t0, 0x1f
+	/* li t0, 0x1f */ /* For MRS proprietary GCC compilers */
+
+    /* Enable nested interrupt, disable hardware stack */
+    li t0, 0x1e /* Refer to RISC-V4 PFIC manual */
+
 	csrw 0x804, t0
 
     /* Enable floating point and interrupt */

CMakeLists.txt

@@ -47,6 +47,7 @@ set(TARGET_C_SOURCES
     "BSP/Peripheral/src/ch32v30x_wwdg.c"
     "src/ch32v30x_it.c"
     "src/main.c"
+    "src/syscalls.c"
     "src/system_ch32v30x.c"
 )
 

src/ch32v30x_it.c

@@ -9,8 +9,8 @@
 *******************************************************************************/
 #include "ch32v30x_it.h"
 
-void NMI_Handler(void) __attribute__((interrupt("WCH-Interrupt-fast")));
-void HardFault_Handler(void) __attribute__((interrupt("WCH-Interrupt-fast")));
+void NMI_Handler(void) __attribute__((interrupt()));
+void HardFault_Handler(void) __attribute__((interrupt()));
 
 /*********************************************************************
  * @fn      NMI_Handler

src/main.c

@@ -1,6 +1,15 @@
 // SPDX-License-Identifier: MIT
 
+#include <stdio.h>
+
+#include <debug.h>
+
 int main(void) {
+
+    USART_Printf_Init(115200);
+
+    printf("Hello world?\r\n");
+
     for(;;) {
         //
     }

src/syscalls.c

@@ -0,0 +1,7 @@
+#include <sys/stat.h>
+
+int _fstat(int file, struct stat *st) {
+  st->st_mode = S_IFCHR;
+
+  return 0;
+}