Index: firmware/App/HDCommon.h
===================================================================
diff -u -rbaa9fb9bb10eed6cd211abaa80e9f9acffdeb20d -rfc12876da6930c955864352182aee2076513a1cc
--- firmware/App/HDCommon.h	(.../HDCommon.h)	(revision baa9fb9bb10eed6cd211abaa80e9f9acffdeb20d)
+++ firmware/App/HDCommon.h	(.../HDCommon.h)	(revision fc12876da6930c955864352182aee2076513a1cc)
@@ -114,8 +114,33 @@
     U08 fpgaMajor;
     U08 fpgaMinor;
     U08 fpgaLab;
+    U32 compatibilityRev;
 } HD_VERSIONS_T;
 
+/// DG version struct.
+typedef struct
+{
+    U08 major;                              ///< DG version major revision
+    U08 minor;                              ///< DG version major revision
+    U08 micro;                              ///< DG version micro revision
+    U16 build;                              ///< DG build version
+    U08 fpgaId;                             ///< DG FPGA ID
+    U08 fpgaMajor;                          ///< DG FPGA major revision
+    U08 fpgaMinor;                          ///< DG FPGA minor revision
+    U08 fpgaLab;                            ///< DG FPGA lab revision
+    U32 compatibilityRev;                   ///< DG compatibility revision
+} DG_VERSIONS_T;
+
+/// Record defining the fields in a UI version request message.
+typedef struct
+{
+    U08                 major;                      ///< Major version for UI software
+    U08                 minor;                      ///< Minor version for UI software
+    U08                 micro;                      ///< Micro version for UI software
+    U16                 build;                      ///< Build number for UI software
+    U32                 compatibility;              ///< Compatibility revision
+} UI_VERSIONS_T;
+
 /// Payload record structure for a peristaltic pump data message.
 typedef struct
 {