diff --git a/main.c b/main.c
index 7741069..d758796 100644
--- a/main.c
+++ b/main.c
@@ -59,6 +59,16 @@ void main()
 	while (1) {
         last_signal = signal;
         signal = ow_reset(OW_PIN);
+
+        if (signal) {
+            ow_write(OW_PIN, 0x33);
+            ow_read_arr(OW_PIN, addr, 8);
+            // check if valid
+            if (addr[0] == 0x00 || (crc8(addr, 7) != addr[7])) {
+                signal = false;
+            }
+        }
+
         if (!signal) {
             if (last_signal) {
                 lcd_clear();
@@ -70,9 +80,6 @@ void main()
                 lcd_clear();
             }
 
-            ow_write(OW_PIN, 0x33);
-            ow_read_arr(OW_PIN, addr, 8);
-
             // Show chip type
             switch (addr[0]) {
                 case 0x10: