diff --git a/apps/px4io/adc.c b/apps/px4io/adc.c
index e06b269dc0..670b8d635d 100644
--- a/apps/px4io/adc.c
+++ b/apps/px4io/adc.c
@@ -154,7 +154,7 @@ adc_measure(unsigned channel)
 	while (!(rSR & ADC_SR_EOC)) {
 
 		/* never spin forever - this will give a bogus result though */
-		if ((hrt_absolute_time() - now) > 1000) {
+		if (hrt_elapsed_time(&now) > 1000) {
 			debug("adc timeout");
 			break;
 		}
diff --git a/apps/px4io/controls.c b/apps/px4io/controls.c
index cad368ae43..6b51647569 100644
--- a/apps/px4io/controls.c
+++ b/apps/px4io/controls.c
@@ -218,7 +218,7 @@ controls_tick() {
 	 * If we haven't seen any new control data in 200ms, assume we
 	 * have lost input.
 	 */
-	if ((hrt_absolute_time() - system_state.rc_channels_timestamp) > 200000) {
+	if (hrt_elapsed_time(&system_state.rc_channels_timestamp) > 200000) {
 		rc_input_lost = true;
 
 		/* clear the input-kind flags here */
@@ -294,7 +294,7 @@ ppm_input(uint16_t *values, uint16_t *num_values)
 	 * If we have received a new PPM frame within the last 200ms, accept it
 	 * and then invalidate it.
 	 */
-	if ((hrt_absolute_time() - ppm_last_valid_decode) < 200000) {
+	if (hrt_elapsed_time(&ppm_last_valid_decode) < 200000) {
 
 		/* PPM data exists, copy it */
 		*num_values = ppm_decoded_channels;
diff --git a/apps/px4io/mixer.cpp b/apps/px4io/mixer.cpp
index 505bc8a699..77f28cd7a6 100644
--- a/apps/px4io/mixer.cpp
+++ b/apps/px4io/mixer.cpp
@@ -88,7 +88,7 @@ void
 mixer_tick(void)
 {
 	/* check that we are receiving fresh data from the FMU */
-	if ((hrt_absolute_time() - system_state.fmu_data_received_time) > FMU_INPUT_DROP_LIMIT_US) {
+	if (hrt_elapsed_time(&system_state.fmu_data_received_time) > FMU_INPUT_DROP_LIMIT_US) {
 
 		/* too long without FMU input, time to go to failsafe */
 		if (r_status_flags & PX4IO_P_STATUS_FLAGS_FMU_OK) {
diff --git a/apps/px4io/px4io.h b/apps/px4io/px4io.h
index 22993fb52f..7b4b07c2c7 100644
--- a/apps/px4io/px4io.h
+++ b/apps/px4io/px4io.h
@@ -105,12 +105,12 @@ extern uint16_t			r_page_servo_failsafe[]; /* PX4IO_PAGE_FAILSAFE_PWM */
  */
 struct sys_state_s {
 
-	uint64_t	rc_channels_timestamp;
+	volatile uint64_t	rc_channels_timestamp;
 
 	/**
 	 * Last FMU receive time, in microseconds since system boot
 	 */
-	uint64_t	fmu_data_received_time;
+	volatile uint64_t	fmu_data_received_time;
 
 };