ANT Forum

Hi,

An activity fit file contains shown below message definition:

I think field #1 is an Dynamic Field. The Reference Field is field #2.

The "FIT Data Transfer Protocol Rev 1.7" describes:

4.5 Dynamic Fields
The interpretation of some message fields depends on the value of another previously defined field.
This is called a DynamicField.

For me, so definitely committed:
First comes the Reference Field, then comes the Dynamic Field.

I understand the protocol wrong?
Is it not hard and fast rule?

I think it's easier to read a fit file if the rule is met.

(and:
even if in Profile.xls the Field Def # Reference Field is larger than the Field Def # Dynamic Field
in fit file must come the Reference Field before the Dynamic Field.

for example Message device_info:

in profile.xls:
device_type Field Def # 1
source_type Field Def # 25

in fit file:
source_type field # x
device_type field # x + n
)


Thank you
edge-python      

To my best knowledge you should NOT rely on sequence of fields.
I don't know how you parse .FIT files, but I found it the easiest way to read in a complete message and parse the complete message (instead of a purely sequential parser).
Btw, the interpretation of the Event.Data field is explained in profile.xls - if you've not already found this info.

Cheers,
OMB      

The SDK allows fields to be written in any order, messages should be fully decoded before interpreting subfields. I will clarify §4.5.      

ShaneP - 10 April 2015 02:21 PM

The SDK allows fields to be written in any order, messages should be fully decoded before interpreting subfields. I will clarify §4.5.

Thanks for the clarification.


For Dynamic Fields I have a further question:

Dynamic Fields based on 1 Reference Field, up to 1 exception:

The Dynamic Field 'target_value' (Message 'workout_step') is based on 2 Reference Fields.

Following description is accurate for all situations?
(or not comprehensive?)



Thank you.
edge-python
     

I look at it more this way:

Messages should not be defined such that more than one reference field condition can be satisfied at once. If this occurs the first one should take priority.

     

Thanks for the answer.

ShaneP - 17 April 2015 01:20 PM

Messages should not be defined such that more than one reference field condition can be satisfied at once.

The FIT SDK example 'WorkoutRepeatGreaterThanStep' contains a message with 2 satisfied reference field condition:

duration_type = 11: repeat_until_hr_greater_than
target_type = 1: heart_rate

the field target_value is interpreted as: target_hr_zone (target_type is the reference field in this case)

ShaneP - 17 April 2015 01:20 PM

If this occurs the first one should take priority.

In the example target_type seems to have the higher priority than duration_type, regardless of the order.

In the example seems to apply:


Thank you.
edge-python
(sorry, english is not my native language)