adding messages needed by progressive imagery and comms manager

ds_acomms_msgs/CMakeLists.txt

@@ -49,17 +49,17 @@ add_message_files(DIRECTORY msg
   FILES
   Vector3_F32.msg
   Point_F32.msg
+  AcksExpected.msg
   AcousticModemData.msg
   MicromodemData.msg
   ModemData.msg
   )
 
 ## Generate services in the 'srv' folder
-# add_service_files(
-#   FILES
-#   Service1.srv
-#   Service2.srv
-# )
+add_service_files(
+  FILES
+  ModemDataRequest.srv
+)
 
 ## Generate actions in the 'action' folder
 # add_action_files(

ds_acomms_msgs/msg/AcksExpected.msg

@@ -0,0 +1,16 @@
+# Progressive Imagery requires acknowlegement for each
+# packet sent, or it tries to resend. This message tells
+# the sender that it *should* have received acks and causes
+# it to reset the queue.
+
+# TODO: In the name of generality, I've split the
+# "reset queue" field from the "please provide data" service,
+# but I don't know if any other nodes will care about this,
+# or what other information should be attached.
+# (Standard header? Time since previous transmit slot?)
+
+# TODO: proper handling of this would require the sender/subsea
+# QM to know the TDMA schedule for the topside QM in order to
+# infer that it _should_ have heard something. Right now,
+# the assumption is that the gap in between two subsea slots
+# always corresponds to a topside slot.

ds_acomms_msgs/srv/ModemDataRequest.srv

@@ -0,0 +1,3 @@
+uint32 bytes_requested
+---
+uint8[] data