diff --git a/Ubiquitous/XiZi_AIoT/hardkernel/uart/printf.h b/Ubiquitous/XiZi_AIoT/hardkernel/uart/printf.h
index 85c030650..93e207e93 100644
--- a/Ubiquitous/XiZi_AIoT/hardkernel/uart/printf.h
+++ b/Ubiquitous/XiZi_AIoT/hardkernel/uart/printf.h
@@ -50,6 +50,7 @@ extern "C" {
 #define KPrintf printf_
 #define printf printf_
 int printf_(const char* format, ...);
+int printf_early(const char* format, ...);
 
 /**
  * Tiny sprintf implementation
diff --git a/Ubiquitous/XiZi_AIoT/hardkernel/uart/uart_common_ope.c b/Ubiquitous/XiZi_AIoT/hardkernel/uart/uart_common_ope.c
index d4a09dfa4..07130da60 100644
--- a/Ubiquitous/XiZi_AIoT/hardkernel/uart/uart_common_ope.c
+++ b/Ubiquitous/XiZi_AIoT/hardkernel/uart/uart_common_ope.c
@@ -895,4 +895,16 @@ int fctprintf(void (*out)(char character, void* arg), void* arg, const char* for
     const int ret = _vsnprintf(_out_fct, (char*)(uintptr_t)&out_fct_wrap, (size_t)-1, format, va);
     va_end(va);
     return ret;
-}
\ No newline at end of file
+}
+
+///////////////////////////////////////////////////////////////////////////////
+__attribute__((weak)) void _debug_uart_putc(int ch);
+int printf_early(const char* format, ...)
+{
+    va_list va;
+    va_start(va, format);
+    char buffer[1];
+    const int ret = _vsnprintf(_debug_uart_putc, buffer, (size_t)-1, format, va);
+    va_end(va);
+    return ret;
+}