diff --git a/Sming/system/m_printf.cpp b/Sming/system/m_printf.cpp
index 03971661ab..507f873e00 100644
--- a/Sming/system/m_printf.cpp
+++ b/Sming/system/m_printf.cpp
@@ -9,7 +9,7 @@ Descr: embedded very simple version of printf with float support
 #include <stdarg.h>
 #include "osapi.h"
 
-#define MPRINTF_BUF_SIZE 256
+#define INITIAL_BUFFSIZE 128
 
 static void defaultPrintChar(uart_t *uart, char c) {
 	return uart_tx_one_char(c);
@@ -62,27 +62,25 @@ int m_snprintf(char* buf, int length, const char *fmt, ...)
 	return n;
 }
 
-int m_vprintf ( const char * format, va_list arg )
+int m_vprintf(const char *fmt, va_list va)
 {
-	if(!cbc_printchar)
-	{
-		return 0;
-	}
-
-	char buf[MPRINTF_BUF_SIZE], *p;
-
-	int n = 0;
-	m_vsnprintf(buf, sizeof(buf), format, arg);
-
-	p = buf;
-	while (p && n < sizeof(buf) && *p)
-	{
-		cbc_printchar(cbc_printchar_uart, *p);
-		n++;
-		p++;
-	}
+    size_t size = INITIAL_BUFFSIZE - 1;
+
+    //  need to retry if size is not big enough
+    while (1) {
+        char buffer[size + 1];
+        size_t sz = m_vsnprintf(buffer, sizeof(buffer), fmt, va);
+        if (sz > size) {
+            size = sz;
+            continue;
+        }
 
-	return n;
+        const char *p = buffer;
+        while (char c = *p++) {
+            cbc_printchar(cbc_printchar_uart, c);
+        }
+        return sz;
+    }
 }
 
 /**