On the Sofar Ocean support page, there are a bunch of helpful links, including Spotter Data Access documentation.
Messages sent with spotter_tx_data
, when viewed using the raw-messages API, can be recognized apart from the other Spotter messages because they will always have 0xDE
as the first byte. The first 29 bytes (including 0xDE
) are a header, and your payload starts at the 30th byte.