Appendix F: Programming API
Documentation: The generic packet format is documented below, as are the specific payloads. These packet types are recommended for new applications targeting the S500 sounder.
Apology: The terms "altitude," "distance," and "depth" are used somewhat interchangeably here. They all mean the sensed distance from the device to some object, which in many applications is "the bottom."
*STR_LEN: Length of the string determined based on payload_length in packet header.
These are the responses that the device will send to the host in response to a general_request packet (id = 6, see above). Alternatively, host may send any one of these packet ids with no payload and device will respond with same id and the payload indicated here.
These packet types can be returned after each ping by specifying their packet id in the report_id field of the set_ping_params packet described above.
distance2 reports a simple distance measurement.
profile6_t report a measure of signal strength at all depths within the ping range. This could be used to present a "waterfall" type display similar to a commercial marine depth sounder or fish finder. The Cerulean SonarView app uses profile6_t to do just that.
The native number of results reported for the profile6_t is 1024 for monotone pings. For chirp pings, the range resolution is affected by the "decimation" field in the set_ping_params command. If decimation is set to 0, the device will vary decimation depending on range. The smallest decimation will be used that does not exceed 6000 reported data elements.
Keep in mind the bandwidth of the communication channel in use when considering which profile report to use. For example, profile6_t can generate a lot of data, and is probably best used with the USB or Ethernet interface.