diff --git a/src/modules/px4iofirmware/i2c.c b/src/modules/px4iofirmware/i2c.c
index 79b6546b39..76762c0fce 100644
--- a/src/modules/px4iofirmware/i2c.c
+++ b/src/modules/px4iofirmware/i2c.c
@@ -331,6 +331,7 @@ i2c_tx_complete(void)
 	i2c_tx_setup();
 }
 
+#ifdef DEBUG
 static void
 i2c_dump(void)
 {
@@ -339,3 +340,4 @@ i2c_dump(void)
 	debug("CCR   0x%08x  TRISE 0x%08x", rCCR,  rTRISE);
 	debug("SR1   0x%08x  SR2   0x%08x", rSR1,  rSR2);
 }
+#endif
diff --git a/src/modules/px4iofirmware/sbus.c b/src/modules/px4iofirmware/sbus.c
index 0e7dc621cf..70ccab1808 100644
--- a/src/modules/px4iofirmware/sbus.c
+++ b/src/modules/px4iofirmware/sbus.c
@@ -119,13 +119,15 @@ sbus_init(const char *device)
 bool
 sbus1_output(uint16_t *values, uint16_t num_values)
 {
-	write(sbus_fd, 'A', 1);
+	char a = 'A';
+	write(sbus_fd, &a, 1);
 }
 
 bool
 sbus2_output(uint16_t *values, uint16_t num_values)
 {
-	write(sbus_fd, 'B', 1);
+	char b = 'B';
+	write(sbus_fd, &b, 1);
 }
 
 bool