I'm looking for information about the fieldId used for creating data fields for the FIT contributor. It seems that this is usually set to 0 for the first field in a watch app, 1 for the second, and so on up to n-1 for the nth field. Is this what is expected?
According to the documentation, the fieldId is "unique", but is it only meant to be unique among other fields for my app?
In experimenting with the fieldId, I made a simple watch app with a single MSG_TYPE_RECORD data field. I ran several versions of the app where the only thing that changed was the fieldId. I tried setting the fieldId value to 0,1, 100, 200, 255, and 256. Each attempt was successful except for 255 and 256. When unsuccessful, I didn't see a plot for the data in the Connect mobile app.
So, does it matter what I use for the fieldId as long as it is different from other fieldIds in the same watch app and is smaller than some limit (perhaps smaller than or equal to 200)?
