added a checksum of the data structure to the gyro board data
diff --git a/gyro_board/src/usb/data_struct.h b/gyro_board/src/usb/data_struct.h
index 718d19c..50eb7a9 100644
--- a/gyro_board/src/usb/data_struct.h
+++ b/gyro_board/src/usb/data_struct.h
@@ -26,6 +26,11 @@
       // dealing with it reset.
       int32_t frame_number;
 
+      // Checksum of this file calculated with sum(1).
+      // The gyro board sets this and then the fitpc checks it to make sure that
+      // they're both using the same version of this file.
+      uint16_t checksum;
+
       // Which robot (+version) the gyro board is sending out data for.
       // We should keep this in the same place for all gyro board software
       // versions so that the fitpc can detect when it's reading from a gyro
@@ -62,7 +67,9 @@
         uint8_t unknown_frame : 1;
       };
     };
-    uint64_t header;
+    struct {
+      uint64_t header0, header1;
+    };
   };
 
   // We are 64-bit aligned at this point.