msg files: add ulog_stream & ulog_stream_ack

msg/CMakeLists.txt

@@ -101,6 +101,8 @@ set(msg_file_names
 	transponder_report.msg
 	uavcan_parameter_request.msg
 	uavcan_parameter_value.msg
+	ulog_stream.msg
+	ulog_stream_ack.msg
 	vehicle_attitude.msg
 	vehicle_attitude_setpoint.msg
 	vehicle_command_ack.msg

msg/ulog_stream.msg

@@ -0,0 +1,16 @@
+# Message to stream ULog data from the logger. Corresponds to the LOGGING_DATA
+# mavlink message
+
+# flags bitmasks
+uint8 FLAGS_NEED_ACK = 1     # if set, this message requires to be acked.
+                             # Acked messages are published synchronous: a
+                             # publisher waits for an ack before sending the
+                             # next message
+
+uint8 length                 # length of data
+uint8 first_message_offset   # offset into data where first message starts. This
+                             # can be used for recovery, when a previous message got lost
+uint16 sequence              # allows determine drops
+uint8 flags                  # see FLAGS_*
+uint8[251] data              # ulog data
+

msg/ulog_stream_ack.msg

@@ -0,0 +1,7 @@
+# Ack a previously sent ulog_stream message that had
+# the NEED_ACK flag set
+
+int32 ACK_TIMEOUT = 300         # timeout waiting for an ack until we retry to send the message [ms]
+int32 ACK_MAX_TRIES = 9         # maximum amount of tries to (re-)send a message, each time waiting ACK_TIMEOUT ms
+
+uint16 sequence