diff --git a/sw/airborne/lisa/lisa_stm_gps_passthrough_main.c b/sw/airborne/lisa/lisa_stm_gps_passthrough_main.c
index db07812097..1b4c103746 100644
--- a/sw/airborne/lisa/lisa_stm_gps_passthrough_main.c
+++ b/sw/airborne/lisa/lisa_stm_gps_passthrough_main.c
@@ -80,7 +80,7 @@ int main(void) {
   main_init();
 
   while (1) {
-    if (sys_time_periodic()) {
+    if (sys_time_check_and_ack_timer(0)) {
       main_periodic();
     }
     main_event();
@@ -92,7 +92,7 @@ int main(void) {
 static inline void main_init(void) {
 
   mcu_init();
-  sys_time_init();
+  sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
   overo_link_init();
 
   uart1_init();
diff --git a/sw/airborne/lisa/lisa_stm_passthrough_main.c b/sw/airborne/lisa/lisa_stm_passthrough_main.c
index 4dfdcc62a1..0d95029419 100644
--- a/sw/airborne/lisa/lisa_stm_passthrough_main.c
+++ b/sw/airborne/lisa/lisa_stm_passthrough_main.c
@@ -95,7 +95,7 @@ int main(void) {
 	main_init();
 
 	while (1) {
-		if (sys_time_periodic())
+		if (sys_time_check_and_ack_timer(0))
 			main_periodic();
 		main_event();
 	}
@@ -106,7 +106,7 @@ int main(void) {
 static inline void main_init(void) {
 
 	mcu_init();
-	sys_time_init();
+	sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
 	imu_init();
 	baro_init();
 	radio_control_init();
diff --git a/sw/airborne/lisa/stm_test_spi_link.c b/sw/airborne/lisa/stm_test_spi_link.c
index f1aa647767..f3aee9cafc 100644
--- a/sw/airborne/lisa/stm_test_spi_link.c
+++ b/sw/airborne/lisa/stm_test_spi_link.c
@@ -43,12 +43,12 @@ static inline void on_overo_link_lost(void);
 int main(void) {
 
   mcu_init();
-  sys_time_init();
+  sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
   overo_link_init();
   DEBUG_SERVO1_INIT();
 
   while (1) {
-    if (sys_time_periodic())
+    if (sys_time_check_and_ack_timer(0))
       main_periodic();
     main_event();
   }
diff --git a/sw/airborne/lisa/test/hs_gyro.c b/sw/airborne/lisa/test/hs_gyro.c
index 8846abb258..111e370f90 100644
--- a/sw/airborne/lisa/test/hs_gyro.c
+++ b/sw/airborne/lisa/test/hs_gyro.c
@@ -51,7 +51,7 @@ static inline void on_mag_event(void);
 int main( void ) {
   main_init();
   while(1) {
-    if (sys_time_periodic())
+    if (sys_time_check_and_ack_timer(0))
       main_periodic_task();
     main_event_task();
   }
@@ -61,7 +61,7 @@ int main( void ) {
 static inline void main_init( void ) {
 
   mcu_init();
-  sys_time_init();
+  sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
   imu_init();
 
   mcu_int_enable();
diff --git a/sw/airborne/lisa/test/lisa_test_actuators_mkk.c b/sw/airborne/lisa/test/lisa_test_actuators_mkk.c
index ef79bcbbec..91eb53353a 100644
--- a/sw/airborne/lisa/test/lisa_test_actuators_mkk.c
+++ b/sw/airborne/lisa/test/lisa_test_actuators_mkk.c
@@ -40,7 +40,7 @@ int main(void) {
   main_init();
 
   while(1) {
-    if (sys_time_periodic())
+    if (sys_time_check_and_ack_timer(0))
       main_periodic_task();
     main_event_task();
   }
@@ -50,7 +50,7 @@ int main(void) {
 
 static inline void main_init( void ) {
   mcu_init();
-  sys_time_init();
+  sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
   actuators_init();
 }
 
diff --git a/sw/airborne/lisa/test/lisa_test_adxl345.c b/sw/airborne/lisa/test/lisa_test_adxl345.c
index 215711adc6..5c058f37c2 100644
--- a/sw/airborne/lisa/test/lisa_test_adxl345.c
+++ b/sw/airborne/lisa/test/lisa_test_adxl345.c
@@ -54,7 +54,7 @@ int main(void) {
   main_init();
 
   while(1) {
-    if (sys_time_periodic())
+    if (sys_time_check_and_ack_timer(0))
       main_periodic_task();
     main_event_task();
   }
@@ -64,7 +64,7 @@ int main(void) {
 
 static inline void main_init( void ) {
   mcu_init();
-  sys_time_init();
+  sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
   main_init_hw();
 
 }
diff --git a/sw/airborne/lisa/test/lisa_test_adxl345_dma.c b/sw/airborne/lisa/test/lisa_test_adxl345_dma.c
index 7befbf6d82..a573a0ef75 100644
--- a/sw/airborne/lisa/test/lisa_test_adxl345_dma.c
+++ b/sw/airborne/lisa/test/lisa_test_adxl345_dma.c
@@ -49,7 +49,7 @@ int main(void) {
   main_init();
 
   while(1) {
-    if (sys_time_periodic())
+    if (sys_time_check_and_ack_timer(0))
       main_periodic_task();
     main_event_task();
   }
@@ -59,7 +59,7 @@ int main(void) {
 
 static inline void main_init( void ) {
   mcu_init();
-  sys_time_init();
+  sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
   main_init_hw();
 
 }
diff --git a/sw/airborne/lisa/test/lisa_test_aspirin.c b/sw/airborne/lisa/test/lisa_test_aspirin.c
index a342e35f5d..1eef11a3af 100644
--- a/sw/airborne/lisa/test/lisa_test_aspirin.c
+++ b/sw/airborne/lisa/test/lisa_test_aspirin.c
@@ -51,7 +51,7 @@ int main(void) {
   main_init();
 
   while(1) {
-    if (sys_time_periodic())
+    if (sys_time_check_and_ack_timer(0))
       main_periodic_task();
     main_event_task();
   }
@@ -61,7 +61,7 @@ int main(void) {
 
 static inline void main_init( void ) {
   mcu_init();
-  sys_time_init();
+  sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
   main_init_hw();
 
   gyro_ready_for_read = FALSE;
diff --git a/sw/airborne/lisa/test/lisa_test_hmc5843.c b/sw/airborne/lisa/test/lisa_test_hmc5843.c
index b2aa3d21e9..c599541b6f 100644
--- a/sw/airborne/lisa/test/lisa_test_hmc5843.c
+++ b/sw/airborne/lisa/test/lisa_test_hmc5843.c
@@ -66,7 +66,7 @@ int main(void) {
   main_init();
 
   while(1) {
-    if (sys_time_periodic())
+    if (sys_time_check_and_ack_timer(0))
       main_periodic_task();
     main_event_task();
   }
@@ -76,7 +76,7 @@ int main(void) {
 
 static inline void main_init( void ) {
   mcu_init();
-  sys_time_init();
+  sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
   main_init_hw();
 }
 
diff --git a/sw/airborne/lisa/test/lisa_test_itg3200.c b/sw/airborne/lisa/test/lisa_test_itg3200.c
index 3dbfeaa3a5..eca40c2994 100644
--- a/sw/airborne/lisa/test/lisa_test_itg3200.c
+++ b/sw/airborne/lisa/test/lisa_test_itg3200.c
@@ -64,7 +64,7 @@ int main(void) {
   main_init();
 
   while(1) {
-    if (sys_time_periodic())
+    if (sys_time_check_and_ack_timer(0))
       main_periodic_task();
     main_event_task();
   }
@@ -74,7 +74,7 @@ int main(void) {
 
 static inline void main_init( void ) {
   mcu_init();
-  sys_time_init();
+  sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
   main_init_hw();
 }
 
diff --git a/sw/airborne/lisa/test/lisa_test_max1168.c b/sw/airborne/lisa/test/lisa_test_max1168.c
index 5e687cc729..73a63e945b 100644
--- a/sw/airborne/lisa/test/lisa_test_max1168.c
+++ b/sw/airborne/lisa/test/lisa_test_max1168.c
@@ -44,7 +44,7 @@ int main(void) {
   main_init();
 
   while(1) {
-    if (sys_time_periodic())
+    if (sys_time_check_and_ack_timer(0))
       main_periodic_task();
     main_event_task();
   }
@@ -55,7 +55,7 @@ int main(void) {
 
 static inline void main_init( void ) {
   mcu_init();
-  sys_time_init();
+  sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
   max1168_init();
   main_spi2_init();
 }
diff --git a/sw/airborne/lisa/test/lisa_test_ms2100.c b/sw/airborne/lisa/test/lisa_test_ms2100.c
index 2433cebbfe..71ec21faab 100644
--- a/sw/airborne/lisa/test/lisa_test_ms2100.c
+++ b/sw/airborne/lisa/test/lisa_test_ms2100.c
@@ -44,7 +44,7 @@ int main(void) {
   main_init();
 
   while(1) {
-    if (sys_time_periodic())
+    if (sys_time_check_and_ack_timer(0))
       main_periodic_task();
     main_event_task();
   }
@@ -55,7 +55,7 @@ int main(void) {
 
 static inline void main_init( void ) {
   mcu_init();
-  sys_time_init();
+  sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
   ms2100_init();
   main_spi2_init();
 }
diff --git a/sw/airborne/lisa/test/lisa_test_sc18is600.c b/sw/airborne/lisa/test/lisa_test_sc18is600.c
index d3f522337b..05cda36c7a 100644
--- a/sw/airborne/lisa/test/lisa_test_sc18is600.c
+++ b/sw/airborne/lisa/test/lisa_test_sc18is600.c
@@ -41,7 +41,7 @@ int main(void) {
   main_init();
 
   while(1) {
-    if (sys_time_periodic())
+    if (sys_time_check_and_ack_timer(0))
       main_periodic_task();
     main_event_task();
   }
@@ -52,7 +52,7 @@ int main(void) {
 
 static inline void main_init( void ) {
   mcu_init();
-  sys_time_init();
+  sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
   sc18is600_init();
   main_spi2_init();
 }
diff --git a/sw/airborne/lisa/test/lisa_tunnel.c b/sw/airborne/lisa/test/lisa_tunnel.c
index c4d27fdbb3..82e5d03277 100644
--- a/sw/airborne/lisa/test/lisa_tunnel.c
+++ b/sw/airborne/lisa/test/lisa_tunnel.c
@@ -36,7 +36,7 @@ static inline void main_event_task( void );
 int main( void ) {
   main_init();
   while(1) {
-    if (sys_time_periodic())
+    if (sys_time_check_and_ack_timer(0))
       main_periodic_task();
     main_event_task();
   }
@@ -45,7 +45,7 @@ int main( void ) {
 
 static inline void main_init( void ) {
   mcu_init();
-  sys_time_init();
+  sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
 }
 
 static inline void main_periodic_task( void ) {
diff --git a/sw/airborne/lisa/test/test_board.c b/sw/airborne/lisa/test/test_board.c
index ef6fb0425a..4f9b27744d 100644
--- a/sw/airborne/lisa/test/test_board.c
+++ b/sw/airborne/lisa/test/test_board.c
@@ -89,7 +89,7 @@ enum TestType cur_test;
 int main( void ) {
   main_init();
   while(1) {
-    if (sys_time_periodic())
+    if (sys_time_check_and_ack_timer(0))
       main_periodic_task();
     main_event_task();
   }
@@ -99,7 +99,7 @@ int main( void ) {
 static inline void main_init( void ) {
 
   mcu_init();
-  sys_time_init();
+  sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
   led_init();
 
   baro_init();
diff --git a/sw/airborne/lisa/test/test_mc_asctec_v1_simple.c b/sw/airborne/lisa/test/test_mc_asctec_v1_simple.c
index 7cc87f2a55..df79cb27ba 100644
--- a/sw/airborne/lisa/test/test_mc_asctec_v1_simple.c
+++ b/sw/airborne/lisa/test/test_mc_asctec_v1_simple.c
@@ -42,7 +42,7 @@ int main(void) {
   main_init();
 
   while(1) {
-    if (sys_time_periodic())
+    if (sys_time_check_and_ack_timer(0))
       main_periodic_task();
     main_event_task();
   }
@@ -52,7 +52,7 @@ int main(void) {
 
 static inline void main_init( void ) {
   mcu_init();
-  sys_time_init();
+  sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
 }
 
 
diff --git a/sw/airborne/lisa/test_adc.c b/sw/airborne/lisa/test_adc.c
index db0b86f6ed..8ad7e125b2 100644
--- a/sw/airborne/lisa/test_adc.c
+++ b/sw/airborne/lisa/test_adc.c
@@ -47,7 +47,7 @@ extern uint8_t adc_new_data_trigger;
 
 static inline void main_init( void ) {
     mcu_init();
-    sys_time_init();
+    sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
     adc_init();
     adc_buf_channel(0, &adc0_buf, 8);
     adc_buf_channel(1, &adc1_buf, 3);
@@ -59,7 +59,7 @@ int main( void ) {
   main_init();
 
   while(1) {
-    if (sys_time_periodic()) {
+    if (sys_time_check_and_ack_timer(0)) {
       main_periodic_task();
     }
     main_event_task();
diff --git a/sw/airborne/lisa/test_csc_servo.c b/sw/airborne/lisa/test_csc_servo.c
index 91b17269fb..82cf5058e5 100644
--- a/sw/airborne/lisa/test_csc_servo.c
+++ b/sw/airborne/lisa/test_csc_servo.c
@@ -52,7 +52,7 @@ int main(void) {
   servos[3] = 4;
 
   while(1) {
-	  if (sys_time_periodic())
+	  if (sys_time_check_and_ack_timer(0))
 		  main_periodic_task();
 	  main_event_task();
   }
@@ -62,7 +62,7 @@ int main(void) {
 
 static inline void main_init( void ) {
 	hw_init();
-	sys_time_init();
+	sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
 	cscp_init();
 	cscp_register_callback(CSC_VANE_MSG_ID, main_on_vane_msg, (void *)&csc_vane_msg);
 }
diff --git a/sw/airborne/lisa/test_datalink.c b/sw/airborne/lisa/test_datalink.c
index 50d9a49e6f..af713a0e7a 100644
--- a/sw/airborne/lisa/test_datalink.c
+++ b/sw/airborne/lisa/test_datalink.c
@@ -39,7 +39,7 @@ int main(void) {
   main_init();
 
   while (1) {
-    if (sys_time_periodic())
+    if (sys_time_check_and_ack_timer(0))
       main_periodic();
     main_event();
   }
@@ -48,7 +48,7 @@ int main(void) {
 
 static inline void main_init( void ) {
   mcu_init();
-  sys_time_init();
+  sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
 }
 
 static inline void main_periodic( void ) {
diff --git a/sw/airborne/lisa/test_float.c b/sw/airborne/lisa/test_float.c
index 4192ba8b5c..b4cdbed9aa 100644
--- a/sw/airborne/lisa/test_float.c
+++ b/sw/airborne/lisa/test_float.c
@@ -36,7 +36,7 @@ int main(void) {
   main_init();
 
   while (1) {
-    if (sys_time_periodic())
+    if (sys_time_check_and_ack_timer(0))
       main_periodic();
   }
   return 0;
@@ -44,7 +44,7 @@ int main(void) {
 
 static inline void main_init( void ) {
   mcu_init();
-  sys_time_init();
+  sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
 }
 
 static inline void main_periodic( void ) {
diff --git a/sw/airborne/lisa/test_mc.c b/sw/airborne/lisa/test_mc.c
index 6cd1ed0d3d..841fd635d5 100644
--- a/sw/airborne/lisa/test_mc.c
+++ b/sw/airborne/lisa/test_mc.c
@@ -45,7 +45,7 @@ int main(void) {
   main_init();
 
   while(1) {
-    if (sys_time_periodic())
+    if (sys_time_check_and_ack_timer(0))
       main_periodic_task();
     main_event_task();
   }
@@ -56,7 +56,7 @@ int main(void) {
 
 static inline void main_init( void ) {
   mcu_init();
-  sys_time_init();
+  sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
   main_i2c_init();
   test_gpios();
 }
diff --git a/sw/airborne/lisa/test_periodic.c b/sw/airborne/lisa/test_periodic.c
index 453c23016d..4a6e25bba9 100644
--- a/sw/airborne/lisa/test_periodic.c
+++ b/sw/airborne/lisa/test_periodic.c
@@ -36,7 +36,7 @@ int main(void) {
   main_init();
 
   while (1) {
-    if (sys_time_periodic())
+    if (sys_time_check_and_ack_timer(0))
       main_periodic();
   }
   return 0;
@@ -44,7 +44,7 @@ int main(void) {
 
 static inline void main_init( void ) {
   mcu_init();
-  sys_time_init();
+  sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
 }
 
 static inline void main_periodic( void ) {
diff --git a/sw/airborne/lisa/test_servos.c b/sw/airborne/lisa/test_servos.c
index 5d177f295a..a0478a011f 100644
--- a/sw/airborne/lisa/test_servos.c
+++ b/sw/airborne/lisa/test_servos.c
@@ -34,7 +34,7 @@ int main(void) {
 
   main_init();
   while (1) {
-    if (sys_time_periodic())
+    if (sys_time_check_and_ack_timer(0))
       main_periodic();
   };
   return 0;
@@ -42,7 +42,7 @@ int main(void) {
 
 static inline void main_init( void ) {
   mcu_init();
-  sys_time_init();
+  sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
   actuators_init();
 }
 
diff --git a/sw/airborne/lisa/test_spi_slave.c b/sw/airborne/lisa/test_spi_slave.c
index e410d7a295..d696e6c2f7 100644
--- a/sw/airborne/lisa/test_spi_slave.c
+++ b/sw/airborne/lisa/test_spi_slave.c
@@ -41,7 +41,7 @@ int main(void) {
   main_init();
 
   while(1) {
-    if (sys_time_periodic())
+    if (sys_time_check_and_ack_timer(0))
       main_periodic_task();
     main_event_task();
   }
@@ -52,7 +52,7 @@ int main(void) {
 
 static inline void main_init( void ) {
   mcu_init();
-  sys_time_init();
+  sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
   main_spi_slave_init();
 }
 
diff --git a/sw/airborne/lisa/test_spi_slave2.c b/sw/airborne/lisa/test_spi_slave2.c
index c1022cbc54..721d4a32d3 100644
--- a/sw/airborne/lisa/test_spi_slave2.c
+++ b/sw/airborne/lisa/test_spi_slave2.c
@@ -49,7 +49,7 @@ int main(void) {
   main_init();
 
   while(1) {
-    if (sys_time_periodic())
+    if (sys_time_check_and_ack_timer(0))
       main_periodic_task();
     main_event_task();
   }
@@ -60,7 +60,7 @@ int main(void) {
 
 static inline void main_init( void ) {
   mcu_init();
-  sys_time_init();
+  sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
   main_spi_slave_init();
 }
 
diff --git a/sw/airborne/lisa/test_uart.c b/sw/airborne/lisa/test_uart.c
index 8224ef6111..2211040aa8 100644
--- a/sw/airborne/lisa/test_uart.c
+++ b/sw/airborne/lisa/test_uart.c
@@ -40,7 +40,7 @@ int main(void) {
   main_init();
 
   while (1) {
-    if (sys_time_periodic())
+    if (sys_time_check_and_ack_timer(0))
       main_periodic();
   }
   return 0;
@@ -48,7 +48,7 @@ int main(void) {
 
 static inline void main_init( void ) {
   mcu_init();
-  sys_time_init();
+  sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
 }
 
 static inline void main_periodic( void ) {