diff --git a/libraries/AP_HAL_PX4/RCInput.cpp b/libraries/AP_HAL_PX4/RCInput.cpp
index 81895c851f..e7c0467a76 100644
--- a/libraries/AP_HAL_PX4/RCInput.cpp
+++ b/libraries/AP_HAL_PX4/RCInput.cpp
@@ -23,7 +23,7 @@ void PX4RCInput::init(void* unused)
 uint8_t PX4RCInput::valid_channels() 
 {
     pthread_mutex_lock(&rcin_mutex);
-    bool valid = _rcin.timestamp != _last_read || _override_valid;
+    bool valid = _rcin.timestamp_last_signal != _last_read || _override_valid;
     pthread_mutex_unlock(&rcin_mutex);
     return valid;
 }
@@ -34,7 +34,7 @@ uint16_t PX4RCInput::read(uint8_t ch)
 		return 0;
 	}
         pthread_mutex_lock(&rcin_mutex);
-	_last_read = _rcin.timestamp;
+	_last_read = _rcin.timestamp_last_signal;
 	_override_valid = false;
 	if (_override[ch]) {
             uint16_t v = _override[ch];
diff --git a/libraries/AP_HAL_PX4/Util.cpp b/libraries/AP_HAL_PX4/Util.cpp
index f32627c099..eefb40f589 100644
--- a/libraries/AP_HAL_PX4/Util.cpp
+++ b/libraries/AP_HAL_PX4/Util.cpp
@@ -11,7 +11,7 @@
 #include "UARTDriver.h"
 #include <uORB/uORB.h>
 #include <uORB/topics/safety.h>
-#include <systemlib/otp.h>
+#include <systemlib/board_serial.h>
 
 extern const AP_HAL::HAL& hal;
 
@@ -105,7 +105,7 @@ bool PX4Util::get_system_id(char buf[40])
 {
     uint8_t serialid[12];
     memset(serialid, 0, sizeof(serialid));
-    val_read(serialid, (const void *)UDID_START, sizeof(serialid));
+    get_board_serial(serialid);
 #ifdef CONFIG_ARCH_BOARD_PX4FMU_V1
     const char *board_type = "PX4v1";
 #else