diff --git a/rtl837x_common.h b/rtl837x_common.h
index 57c0e6a..daea67a 100644
--- a/rtl837x_common.h
+++ b/rtl837x_common.h
@@ -88,6 +88,7 @@ void print_string(__code char *p);
 void print_long(__xdata uint32_t a);
 void print_short(uint16_t a);
 void print_byte(uint8_t a);
+void itoa(uint8_t v);
 void print_sfr_data(void);
 void print_phy_data(void);
 void phy_write_mask(uint16_t phy_mask, uint8_t dev_id, uint16_t reg, uint16_t v);
diff --git a/rtlplayground.c b/rtlplayground.c
index 8bc0730..1690b7c 100644
--- a/rtlplayground.c
+++ b/rtlplayground.c
@@ -172,6 +172,22 @@ void write_char(char c)
 }
 
 
+void itoa(uint8_t v)
+{
+	uint8_t t = (v / 100);
+	// when print_zeros is not zero, we know that a non-zero number has printed.
+	// That have to print all the next numbers.
+	uint8_t print_zeros = t;
+	if (print_zeros)
+		write_char('0' + t);
+	t = (v / 10) % 10;
+	print_zeros |= t;
+	if (print_zeros)
+		write_char('0' + t);
+	write_char('0' + (v % 10));
+}
+
+
 void print_string(__code char *p)
 {
 	while (*p)