Third-Party Data Field Limit is 2, Not 4

What how? Why did not anyone mention this sooner? Was this broken with a firmware update?

Hi there,
This problem started with the penultimate update 15.31, in the activities of hiking and strength training some data fields are either no longer selectable or are not displayed at all.
Deleting and reinserting the data fields did not change anything, nor did reinstalling them.

MfG

DK

Garmin-Laurie What's going on here, does the watch have the described features (allowing 4 IQ datafields) or does it not?

I'm on 15.32. Have tested this using a combination of fields and it doesn't work.  Garmin seems to thing that because they can create a screen that shows 4 third-party fields, the problem doesn't exits. Wrong! What they don't seem to understand is that when you have the actual sensors and you begin the Activity, only 2 fields will transmit data. The other ones will display an error to revert to the Timer field. 

TL;DR sounds like you're running into an undocumented limit on the number of 3rd-party data ("developer fields") that can be written to the FIT file by all CIQ data fields in a single activity profile, not a hard limit on the number of CIQ data fields that can be added. As you posted, you are actually able to add 4 CIQ data fields to an activity. It's just that some of them will crash when they actually try to write data.

In the past, for watches with a 2-CIQ field limit, the limit on developer fields has been 16. For example, suppose I install Stryd Zones on my Run activity on my FR955 (with a 2 CIQ field limit). Let's say, for the sake of argument, that Stryd Zones records 10 developer fields (e.g. Power, Leg Spring Stiffness, etc.). This means I cannot install another CIQ data field which records more than 6 fields, otherwise one CIQ field or the other will crash.

More details:

neskery said:

I'm trying to bring in Stryd (running power), 80/20 Zones, Dexcom (blood glucose), and Core (core body temperature).

neskery said:

Wrong! What they don't seem to understand is that when you have the actual sensors and you begin the Activity, only 2 fields will transmit data. The other ones will display an error to revert to the Timer field. 

If I'm understanding you correctly, most [or all] of those fields write 3rd-party data to the activity FIT file.

There is indeed a limit to how much 3rd-party data ["developer data" / "developer fields"] can be written to the FIT file, and this has always been on a per-activity basis, *not* a per-data field basis. My understanding is that this limit exists to save memory.

Notably, this been an issue in the past, even when Connect IQ data field limit was 2 fields for watches. That's why some 3rd party data fields have the option to disable or limit the recording of data.

In your case, it sounds like you're running into the per-activity developer data limit, which is independent of the the limit on the number of CIQ data fields. It could be the case that while Garmin legit raised the CIQ data field limit from 2 to 4, they did *not* raise the limit on developer data (or they raised it insufficiently to cover your use case).

I bet that if you installed 4 CIQ data fields which don't record any data at all, you wouldn't have this problem. Or perhaps you could get away with installing 3 CIQ fields which record data, as long as none of them record *too* much data. There's probably situations where you could install 4 CIQ fields which record small amounts of data, too.

So it's not quite right to say that the "third-party data field limit is 2, not 4". I think it would be more accurate to say that it's not practical to have 4 third-party data fields, in the case that they all record developer data. But even in the past, we could say that it's not practical to have 2 third-party data fields, in the case that they both record lots of developer data. That's why a Stryd support article recommends uninstalling all other CIQ data fields. They know that Stryd Zones records a lot of data, and they know that other CIQ data fields can potentially conflict with their data field, even though you can "only" select 2 fields per activity.

As far as the actual limit goes, historically, it seems that there has been a per-activity limit of 16 developer fields (at least for watches) - this applies to watches that had the 2 CIQ field limit.

You would think that Garmin would've doubled this limit to 32 for watches that have a 4-field limit, but who knows.

If anyone actually wants to investigate this limit, there's a CIQ data field which allows you to modify the amount of developer data that's written, for testing purposes. If you install this CIQ data field [without installing any other CIQ fields], you could tweak the limits and see what it takes to make it crash:

https://apps.garmin.com/apps/2e8bf443-f030-4bee-b816-35f5eb404550 

To be clear, just as older watches nominally allow 2 CIQ data fields but sometimes you can't use 2 fields *in practice* because they collectively write too much 3rd-party data, it seems to be the case that Fenix 8 does allow 4 CIQ data fields, but sometimes it doesn't work *in practice* (due to writing too much data).

Iow this is nothing new, but it may be more of an issue than before, assuming that the limit on 3rd-party data has not been increased to match the increase in the allowed number of CIQ data fields.

Either way, there will always be a limit on the amount of 3rd-party data that can be written, and it will always be the case that *some* combo of CIQ data fields can potentially cause a crash, unfortunately. This is because:

- the limit is for all CIQ data fields (in a given activity profile), not on individual CIQ data fields

- it's not possible for a CIQ data field to notice that other CIQ data fields are writing too much data and change its behaviour proactively

- it's not possible for a CIQ data field to gracefully fail to write data if the total limit is exceeded

It's not the greatest design, but it is what it is. In a perfect world, it would be nice if CIQ data fields could gracefully fail and recover when the total limit is exceeded, but in reality, the onus is placed on the user to either choose a combo of data fields that doesn't exceed the limit, or, when applicable, to use the settings of CIQ data fields which allow you to disable or limit recording.

Very helpful - thanks for posting!

If Garmin says you can use 4 the expectation is I can use 4 without any limitations.

Correct would be to state "you can use 4 now*" and then describing the limitations *