diff --git a/atusb/fw/board.c b/atusb/fw/board.c
index 03fd1c8..dc507e3 100644
--- a/atusb/fw/board.c
+++ b/atusb/fw/board.c
@@ -1,8 +1,8 @@
 /*
  * fw/board.c - Board-specific functions (for boot loader and application)
  *
- * Written 2011 by Werner Almesberger
- * Copyright 2011 Werner Almesberger
+ * Written 2011, 2013 by Werner Almesberger
+ * Copyright 2011, 2013 Werner Almesberger
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -11,6 +11,7 @@
  */
 
 
+#include <stdbool.h>
 #include <stdint.h>
 
 #include <avr/io.h>
@@ -81,7 +82,7 @@ void reset_rf(void)
 }
 
 
-void led(int on)
+void led(bool on)
 {
 	if (on)
 		SET(LED);
@@ -111,7 +112,7 @@ static char hex(uint8_t nibble)
 static void get_sernum(void)
 {
 	uint8_t sig;
-	int i;
+	uint8_t i;
 
 	for (i = 0; i != 10; i++) {
 		sig = boot_signature_byte_get(i+0xe);
diff --git a/atusb/fw/board.h b/atusb/fw/board.h
index bb0b2cc..7cbdca6 100644
--- a/atusb/fw/board.h
+++ b/atusb/fw/board.h
@@ -82,7 +82,7 @@ void reset_cpu(void);
 uint8_t read_irq(void);
 void slp_tr(void);
 
-void led(int on);
+void led(bool on);
 void panic(void);
 
 uint64_t timer_read(void);
diff --git a/atusb/fw/mac.c b/atusb/fw/mac.c
index 9030dce..86f57f3 100644
--- a/atusb/fw/mac.c
+++ b/atusb/fw/mac.c
@@ -22,7 +22,7 @@
 #include "mac.h"
 
 
-int (*mac_irq)(void) = NULL;
+bool (*mac_irq)(void) = NULL;
 
 
 static uint8_t rx_buf[MAX_PSDU+2]; /* PHDR+payload+LQ */
@@ -64,7 +64,7 @@ static void rx_done(void *user)
 }
 
 
-static int handle_irq(void)
+static bool handle_irq(void)
 {
 	uint8_t irq;
 	uint8_t size, i;
diff --git a/atusb/fw/mac.h b/atusb/fw/mac.h
index 6b06730..ca7caff 100644
--- a/atusb/fw/mac.h
+++ b/atusb/fw/mac.h
@@ -17,7 +17,7 @@
 #include <stdint.h>
 
 
-extern int (*mac_irq)(void);
+extern bool (*mac_irq)(void);
 
 bool mac_rx(int on);
 bool mac_tx(uint16_t flags, uint16_t len);