Questions about left/right balance and its decodification

Hello:

I see in the Profile.xlsx file that there are two "Type Name" registers related to left/right balance of power:

left_right_balance, of type uint8 (mask 0x7F and right 0x80), and

left_right_balance_100, of type uint16 (mask 0x3FFF and right 0x8000)

Are these two different fields?, i.e., can be devices that store left_right_balance and others that store left_right_balance_100?

Another question is: is always the stored value the value for the right leg? I understand that according to the Profile.xlsx. Other implementations switching between left and right legs does not complain the standard. Am I right?

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0 Ben FIT 19 days ago

The left_right_balance_100 fields are are found in the summary messages. For example the Session and Lap messages. A better name for those fields would have been avg_left_right_balance. The scale of 100 is so that the average values does not need to be rounded to a whole number. The left_right_balance field is only found in the Record mesgs.

Encoded in each value is a bit that indicates if the value is for the left or right side. The other bits are the value itself. The "right" and "mask" bit-masks are in the Profile.xlsx as well as enums or #defines in the SDKs.

This is how the masks are used:

is_right = left_right_balance_100 & 0x8000

value = left_right_balance_100 & 0x3FFF

For example:

left_right_balance_100 = 0x932E

is_right = 0x8031 & 0x8000 = true

value = 0x8031 & 0x3FFF = 49100

value_scaled = 49100 / 100 = 49.1%

For the left_right_balance in the Record message the value does not need to be divided by 100, and the masks are:

isRight = left_right_balance & 0x80

value left_right_balance & 0x7F

0 jgpallero 18 days ago in reply to Ben FIT

Thank you very much for your answer, Ben. I also understand that if isRight=left_right_balance & 0x80 is zero the value of left_right_balance is useless. Am I right?

0 Ben FIT 18 days ago in reply to jgpallero

If (left_right_balance & 0x80 == zero), then the value is the balance for the left leg.

0 jgpallero 17 days ago in reply to Ben FIT

Thank you for your answer. From now on, I continue this discussion in forums.garmin.com/.../running-cpp-examples-decode-decode-cpp-program-and-strange-behavior-with-two-fit-files-from-different-devices