diff --git a/lib/sensor_sdm120.c b/lib/sensor_sdm120.c
index f3a421c..eff2ae0 100644
--- a/lib/sensor_sdm120.c
+++ b/lib/sensor_sdm120.c
@@ -63,14 +63,14 @@ static volatile uint8_t tx_used = 0; /**< number of byte to transmit */
 
 volatile bool sensor_sdm120_measurement_received = false;
 
-/**< the ModBus timeouts to respect for sending messages **/
+/** the ModBus timeouts to respect for sending messages **/
 static enum timeout_t {
 	TIMEOUT_BEGIN = 0, /**< silent time before sending data */
 	TIMEOUT_END, /**< silent time after sending data */
 	TIMEOUT_BETWEEN, /**< time to wait between messages */
-	TIMEOUT_MAX
-} timeout;
-/**< current timeout used */
+	TIMEOUT_MAX /**< last element (useful to no the number of elements) */
+} timeout; /**< the current timeout used */
+/** current timeout used */
 static uint16_t timeout_times[TIMEOUT_MAX] = {0};
 
 /** SDM120 3xxxx input register start addresses for the measurement types */ 
@@ -343,6 +343,7 @@ void USART_ISR(SENSOR_SDM120_USART)(void)
 	}
 }
 
+/** interrupt service routine called on timeout */
 void TIM_ISR(SENSOR_SDM120_TIMER)(void)
 {
 	if (timer_get_flag(TIM(SENSOR_SDM120_TIMER), TIM_SR_UIF)) { // update event happened