diff --git a/main.c b/main.c
index 7357014..2dcc1d5 100644
--- a/main.c
+++ b/main.c
@@ -11,6 +11,9 @@
 #include "main.h"
 #include "softi2c_master.h"
 
+// enable UART debug
+#define DEBUG 0
+
 #define EEPROM_ADDR 0x4000 // EEPROM start address
 static bool eeprom_valid = true; // if the EDID can be read from EEPROM
 // LED pin (sink for on)
@@ -57,23 +60,22 @@ static void wait_10us(uint32_t us10)
 
 void putc(char c)
 {
+	(void)c;
+	IWDG_KR = IWDG_KR_KEY_REFRESH; // reset watchdog
+#if DEBUG
 	while (!UART1->SR.fields.TXE); // wait until TX buffer is empty
 	UART1->DR.reg = c; // put character in buffer to be transmitted
 	// don't wait until the transmission is complete
+#endif
 }
 
-// enable/disable UART debug
-//#define puts(X) {}
-#define puts(X) puts_uart(X)
-
-void puts_uart(const char* s)
+void puts(const char* s)
 {
 	if (NULL == s) {
 		return;
 	}
 	while (*s) {
 		putc(*s++);
-		IWDG_KR = IWDG_KR_KEY_REFRESH; // reset watchdog
 	}
 }
 
@@ -81,10 +83,11 @@ void putn(uint8_t n)
 {
 	n &= 0x0f; // ensure it's a nibble
 	if (n < 0xa) {
-		putc('0' + n);
+		n += '0';
 	} else {
-		putc('a' + (n - 0x0a));
+		n = 'a' + (n - 0x0a);
 	}
+	putc(n);
 }
 
 void puth(uint8_t h)