Change behavior to:

1. Printf will wait up to 120ms at boot.
2. If printf has timed out, it will immediately continue.
3. If a debugger is reattached, it will keep printing.
4. If a debugger is attached, it will wait up to 120ms. Then continue at full speed.

ch32v003fun/ch32v003fun.c

@@ -761,9 +761,12 @@ extern uint32_t * _edata;
 // If you don't override a specific handler, it will just spin forever.
 void DefaultIRQHandler( void )
 {
-#if FUNCONF_DEBUG_HARDFAULT
-	// Wait indefinitely for a debugger to attach.
-	while( !DidDebuggerAttach() );
+#if FUNCONF_DEBUG_HARDFAULT && ( FUNCONF_USE_DEBUGPRINTF || FUNCONF_USE_UARTPRINTF )
+#if FUNCONF_USE_DEBUGPRINTF
+	// Wait indefinitely for a printf to become clear.
+	while( !DebugPrintfBufferFree() );
+
+#endif
 	printf( "DEAD MSTATUS:%08x MTVAL:%08x MCAUSE:%08x MEPC:%08x\n", (int)__get_MSTATUS(), (int)__get_MTVAL(), (int)__get_MCAUSE(), (int)__get_MEPC() );
 #endif
 	// Infinite Loop
@@ -1587,7 +1590,7 @@ static void internal_handle_input( volatile uint32_t * dmdata0 )
 {
 	uint32_t dmd0 = *dmdata0;
 	int bytes = (dmd0 & 0x3f) - 4;
-	if( bytes > 0 )
+	if( bytes > 0 && bytes < 16 )
 	{
 		handle_debug_input( bytes, ((uint8_t*)dmdata0) + 1 );
 	}
@@ -1609,14 +1612,18 @@ void poll_input( void )
 //           MSB .... LSB
 // DMDATA0: char3 char2 char1 [status word]
 // where [status word] is:
-//   b7 = is a "printf" waiting?
-//   b0..b3 = # of bytes in printf (+4).  (5 or higher indicates a print of some kind)
+//   bit 7 = is a "printf" waiting?
+//   bit 6 = printf has timed out.
+//   bit 0..bit 3 = # of bytes in printf (+4).  (5 or higher indicates a print of some kind)
 //     note: if b7 is 0 in reply, but b0..b3 have >=4 then we received data from host.
+// Special sentinel:
+//     status word = 0x80 = default at start
+//     status word = 0xcx = timed out.
 // declare as weak to allow overriding.
 WEAK int _write(int fd, const char *buf, int size)
 {
 	(void)fd;
-	if( !DidDebuggerAttach() ) return;
+	if( ( *DMDATA0 & 0xc0 ) == 0xc0 ) return 0;
 
 	char buffer[4] = { 0 };
 	int place = 0;
@@ -1634,7 +1641,13 @@ WEAK int _write(int fd, const char *buf, int size)
 		if( tosend > 7 ) tosend = 7;
 
 		while( ( lastdmd = (*DMDATA0) ) & 0x80 )
-			if( timeout-- == 0 ) return place;
+		{
+			if( timeout-- == 0 )
+			{
+				*DMDATA0 |= 0xc0;
+				return 0;
+			}
+		}
 
 		if( lastdmd ) internal_handle_input( (uint32_t*)DMDATA0 );
 
@@ -1665,16 +1678,24 @@ WEAK int _write(int fd, const char *buf, int size)
 // single to debug intf
 WEAK int putchar(int c)
 {
-	if( !DidDebuggerAttach() ) return;
+	if( ( *DMDATA0 & 0xc0 ) == 0xc0 ) return 0;
 
 	int timeout = FUNCONF_DEBUGPRINTF_TIMEOUT;
 	uint32_t lastdmd = 0;
 
 	while( ( lastdmd = (*DMDATA0) ) & 0x80 )
-		if( timeout-- == 0 ) return 0;
+	{
+		if( timeout-- == 0 )
+		{
+			*DMDATA0 |= 0xc0;
+			return 0;
+		}
+	}
 
 	// Simply seeking input.
 	if( lastdmd ) internal_handle_input( (uint32_t*)DMDATA0 );
+
+	// Write out character.
 	*DMDATA0 = 0x85 | ((const char)c<<8);
 	return 1;
 }

ch32v003fun/ch32v003fun.h

@@ -50,10 +50,10 @@
     8. Default debug behavior, when semihosting:
         a. You get access to DidDebuggerAttach() - so you can see if a debugger has attached.
         b. WaitForDebuggerToAttach( int timeout_ms ) - if timeout_ms == 0, will wait for forever.
-        c. If a debugger has attached, printf will wait 120ms (configurable) to make sure it
-           doesn't drop data.  Otherwise, printf fast-path's to exit.  It will still do the string
+        c. printf will wait 120ms (configurable) to make sure it doesn't drop data.  Otherwise,
+           printf will fast-path to exit after the first timeout. It will still do the string
            formatting, but will not wait on output. Timeout is configured with
-           FUNCONF_DEBUGPRINTF_TIMEOUT
+           FUNCONF_DEBUGPRINTF_TIMEOUT.
         d. If you hard fault, it will wait indefinitely for a debugger to attach, once attached,
            will printf the fault cause, and the memory address of the fault. Space can be saved
            by setting FUNCONF_DEBUG_HARDFAULT to 0.
@@ -14007,9 +14007,10 @@ void SetupUART( int uartBRR );
 int WaitForDebuggerToAttach( int timeout_ms );
 
 // Returns 1 if a debugger has activated the debug module.
-#if defined(__riscv) || defined(__riscv__)
-inline static int DidDebuggerAttach() { return !*DMSTATUS_SENTINEL; }
-#endif
+#define DidDebuggerAttach() (!*DMSTATUS_SENTINEL)
+
+// Returns 1 if a debugger has activated the debug module.
+#define DebugPrintfBufferFree() (!(*DMDATA0 & 0x80))
 
 // Just a definition to the internal _write function.
 int _write(int fd, const char *buf, int size);

examples/debugprintfdemo/debugprintfdemo.c

@@ -17,6 +17,8 @@ int main()
 {
 	SystemInit();
 
+	while( !DebugPrintfBufferFree() );
+
 	// Enable GPIOs
 	RCC->APB2PCENR |= RCC_APB2Periph_GPIOD | RCC_APB2Periph_GPIOC;
 

examples/debugprintfdemo/funconfig.h

@@ -3,7 +3,7 @@
 
 // Though this should be on by default we can extra force it on.
 #define FUNCONF_USE_DEBUGPRINTF 1
-#define FUNCONF_DEBUGPRINTF_TIMEOUT (1<<31) // Wait for a very very long time.
+//#define FUNCONF_DEBUGPRINTF_TIMEOUT (1<<31) // Optionally, wait for a very very long time on every printf.
 
 #define CH32V003           1