diff --git a/Core/Src/sts_cmox_hmac_sha.c b/Core/Src/sts_cmox_hmac_sha.c
index 195d98f..65b4979 100644
--- a/Core/Src/sts_cmox_hmac_sha.c
+++ b/Core/Src/sts_cmox_hmac_sha.c
@@ -41,11 +41,7 @@ uint32_t sts_hmac_verify(void)
 	GetUniqueId(uid);
 
 	ret = sts_hmac_sha1((const uint8_t *) mKey, sizeof(mKey), (const uint8_t*)(uid+4), 4, &hmac_result);
-/*
-	for (i=0;i<sizeof(Computed_Tag_SHA1); i++) {
-			APP_LOG(TS_OFF,VLEVEL_M,"0x%02x ", hmac_result.hmac_tag[i]);
-	}
-*/
+
 	ret = memcmp(hmac_result.hmac_tag, (void *)sts_ac_code, sizeof(sts_ac_code));
 
 	hmac_result.ac_pass  = (ret == 0x0)?1U:0U;
diff --git a/TOF/App/app_tof_vl53l0x_range.c b/TOF/App/app_tof_vl53l0x_range.c
index 83d4d2b..f53d5a1 100644
--- a/TOF/App/app_tof_vl53l0x_range.c
+++ b/TOF/App/app_tof_vl53l0x_range.c
@@ -44,7 +44,7 @@
  * @defgroup ErrCode Errors code shown on display
  * @{
  */
-#define		STS_MAX_L0_RANGE		((uint32_t) 2000)
+#define		STS_MAX_L0_RANGE		((uint32_t) 1000)
 #define ERR_DETECT             -1
 #define ERR_DEMO_RANGE_ONE     1
 #define ERR_DEMO_RANGE_MULTI   2
@@ -154,7 +154,7 @@ int sts_tof_vl53l0x_DetectSensors(void)
 	   do {
 		   /* Set I2C standard mode (400 KHz) before doing the first register access */
 		   //if (status == VL53L0X_ERROR_NONE)
-		   //status = VL53L0X_WrByte(pDev, 0x88, 0x00);
+		   status = VL53L0X_WrByte(pDev, 0x88, 0x00);
 
 		   /* Try to read one register using default 0x52 address */
 		   status = VL53L0X_RdWord(pDev, VL53L0X_REG_IDENTIFICATION_MODEL_ID, &Id);
@@ -173,21 +173,26 @@ int sts_tof_vl53l0x_DetectSensors(void)
 			   pDev->I2cDevAddr = FinalAddress;
 			   /* Check all is OK with the new I2C address and initialize the sensor */
 			   status = VL53L0X_RdWord(pDev, VL53L0X_REG_IDENTIFICATION_MODEL_ID, &Id);
+			   if (status !=0)
+			   {
+			  	   APP_LOG(TS_OFF, VLEVEL_H, "#i VL53L0X_RdWord fail\r\n");
+			  	   break;
+			  	}
 			   status = VL53L0X_DataInit(pDev);
 			   if( status == 0 ){
 				   pDev->Present = 1;
 				   //APP_LOG(TS_OFF, VLEVEL_H, "#%u VL53L0X_SetDeviceAddress to 0x%02x\r\n",i, pDev->I2cDevAddr);
 
-				   nDevPresent++;
-				   nDevMask |= 1 << i;
-				   pDev->Present = 1;
-				   APP_LOG(TS_OFF, VLEVEL_H, "VL53L0X %d Present and initiated to final 0x%2x,  Position Mask=0x%02x\r\n", pDev->Id, pDev->I2cDevAddr, nDevMask);
 
 			   }
 			   else{
 				   APP_LOG(TS_OFF, VLEVEL_H, "VL53L0X_DataInit %d fail\r\n", Id);
 				   break;
 			   }
+			   nDevPresent++;
+			   nDevMask |= 1 << i;
+			   pDev->Present = 1;
+			   APP_LOG(TS_OFF, VLEVEL_H, "VL53L0X %d Present and initiated to final 0x%2x,  Position Mask=0x%02x\r\n", pDev->Id, pDev->I2cDevAddr, nDevMask);
 
 		   } else {
 			   APP_LOG(TS_OFF, VLEVEL_H, "# unknown ID %x\r\n", Id);
@@ -368,9 +373,9 @@ void STS_TOF_VL53L0X_Range_Process(void)
 	  nSensorPresent = sts_tof_vl53l0x_DetectSensors();					// confirm sensor online
 	  APP_LOG(TS_OFF, VLEVEL_H, "\r\n %u pcs sensor(s) online \r\n", nSensorPresent);
   }
-  sts_tof_distance_data[0] = STS_MAX_L0_RANGE;
-  sts_tof_distance_data[1] = STS_MAX_L0_RANGE;
-  sts_tof_distance_data[2] = STS_MAX_L0_RANGE;
+  sts_tof_distance_data[0] = 0;
+  sts_tof_distance_data[1] = 0;
+  sts_tof_distance_data[2] = 0;
 
   if (nSensorPresent > 0)
   {
@@ -382,33 +387,40 @@ void STS_TOF_VL53L0X_Range_Process(void)
 	  {
 		  if (VL53L0XDevs[i].Present ==1)
 		  {
-			status = VL53L0X_PerformSingleRangingMeasurement(&VL53L0XDevs[i], &RangingMeasurementData);
-			if( status ==0 )
-			{
-				sts_tof_vl53l0x_Sensor_SetNewRange(&VL53L0XDevs[i],&RangingMeasurementData);
-				if( RangingMeasurementData.RangeStatus == 0 )
+			uint8_t rep=0;
+			do {
+				rep++;
+				status = VL53L0X_PerformSingleRangingMeasurement(&VL53L0XDevs[i], &RangingMeasurementData);
+				if (status ==0)
 				{
-				  sts_tof_distance_data[i] = (int)VL53L0XDevs[i].LeakyRange;
-				  if (sts_tof_distance_data[i] ==0) sts_tof_distance_data[i]+= STS_MAX_L0_RANGE;
-		  		  nDevMask |= (1 << i);
-		  		  sensor_data_ready |= 1;
-				 }  else
-			  	 {
-			  		//HandleError(ERR_DEMO_RANGE_ONE);
-					 APP_LOG(TS_OFF, VLEVEL_H,"\r\n#%u sensor   ERR code = %04u\r\n",i, ERR_DEMO_RANGE_ONE);
-			  	 }
-			  	// ##########     two conditions
-			  	// ##########     1) return status ==0,
-			  	// ##########     2) and ranging status for valid ranging value !!!!!!!!!!!!!!!!!
-			}
-		  }
+					sts_tof_vl53l0x_Sensor_SetNewRange(&VL53L0XDevs[i],&RangingMeasurementData);
+					if( RangingMeasurementData.RangeStatus == 0 )
+					{
+						sts_tof_distance_data[i] = (int)VL53L0XDevs[i].LeakyRange;
 
-		  HAL_Delay(30);
-	  }  // for i < MAX_TOF_COUNT
-	  if (sensor_data_ready != 0) {
-		  APP_LOG(TS_OFF, VLEVEL_H, "\r\n## Measured Range: \r\nTOF #0 = %4u mm, \r\nTOF #1 = %4u mm, \r\nTOF #2 = %4u mm\r\n",
+						nDevMask |= (1 << i);
+						sensor_data_ready |= 1;
+					}  else
+					{
+						//HandleError(ERR_DEMO_RANGE_ONE);
+						APP_LOG(TS_OFF, VLEVEL_H,"\r\n#%u sensor   ERR code = %04u\r\n",i, ERR_DEMO_RANGE_ONE);
+					}
+						// ##########     two conditions
+						// ##########     1) return status ==0,
+						// ##########     2) and ranging status for valid ranging value !!!!!!!!!!!!!!!!!
+					}
+					HAL_Delay(1);
+				} while ((RangingMeasurementData.RangeStatus != 0)&&(rep <10));
+				sts_tof_distance_data[i] = (RangingMeasurementData.RangeStatus!=0)?STS_MAX_L0_RANGE:sts_tof_distance_data[i];
+		    }
+
+		    HAL_Delay(5);
+	      }  // for i < MAX_TOF_COUNT
+
+	      if (sensor_data_ready != 0) {
+	    	  APP_LOG(TS_OFF, VLEVEL_H, "\r\n## Measured Range: \r\nTOF #0 = %4u mm, \r\nTOF #1 = %4u mm, \r\nTOF #2 = %4u mm\r\n",
 				  (int)sts_tof_distance_data[0],(int)sts_tof_distance_data[1],(int)sts_tof_distance_data[2]);
-	  }
+	      }
 
   }   // nSensorPresent >0