diff --git a/libraries/AP_Mount/AP_Mount_Topotek.h b/libraries/AP_Mount/AP_Mount_Topotek.h
index 9da82d1e6abb4..c1f3e08dc8fa1 100755
--- a/libraries/AP_Mount/AP_Mount_Topotek.h
+++ b/libraries/AP_Mount/AP_Mount_Topotek.h
@@ -115,19 +115,19 @@ class AP_Mount_Topotek : public AP_Mount_Backend_Serial
     // address (2nd and 3rd bytes of packet)
     // first byte is always U followed by one of the other options
     enum class AddressByte : uint8_t {
-        UART = 'U',
-        LENS = 'M',
-        SYSTEM_AND_IMAGE = 'D',
-        AUXILIARY_EQUIPMENT = 'E',
-        NETWORK = 'P',
-        GIMBAL = 'G',
+        SYSTEM_AND_IMAGE = 68,      // 'D'
+        AUXILIARY_EQUIPMENT = 69,   // 'E'
+        GIMBAL = 71,                // 'G'
+        LENS = 77,                  // 'M'
+        NETWORK = 80,               // 'P'
+        UART = 85,                  // 'U'
     };
 
     // control byte (read or write)
     // sent as 7th byte of packet
     enum class ControlByte : uint8_t {
-        READ = 'r',
-        WRITE = 'w',
+        READ = 114,     // 'r'
+        WRITE = 119,    // 'w'
     };
 
     // parsing state