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Development Team Member
Posts: 55
I have another annoying problem with Garmin Fenix 3
(and probably has nothing to do with Moxy).

I customize Run app where I changed several screens to 
show Moxy Data Field. When I select "ConnectIQ" Fields
to choose Moxy field, I often get a message: 
"Replace or remove a Connect IQ field on any data screen
to add another".

I do have Moxy succesfully connected in two other data screens.
Is there a limit on how many Connect IQ fields can be conected
in an app?

If there is a limit, is there a way to get around it?


Posts: 236
Hi Runner,

The fenix 3 is limited to 2 CIQ data fields installed at once.

I can't think of a work around for the Fenix 3 the way it works now.

I have not done any testing with the same data field loaded on 2 different screens.  I'm not sure exactly how this works in the code on the watch.  I don't know why 2 copies of the same data field counts against the 2 data field limit.  I will post a question on this in the CIQ forum.


Development Team Member
Posts: 55
Heart rate field doesn't suffer from this limitation.

Is there a reason why Moxy sensor is not registered as a sensor
(under Settings->Sensors->Add New) in Fenix3 and then used
for data fields that way?

Does the same limitation apply for customs app like Moxy Run?
Namely, if you wrote a custom app would you be able to display
Moxy data in more than two screens?



Posts: 236
Hi runner,

The "native" and the "CIQ" data fields are very different in the background.  The Fenix 3 does not support the muscle oxygen profile natively so we need to write the CIQ data field code ourselves.  This code specifies the parameters for the radio communication and what gets displayed in the fields and what gets written to the FIT file.

When you load a CIQ data field, it makes the watch run that extra code.  That's why they limit you to 2.

When you load the same data field on 2 separate data screens, it only actually runs 1 extra bit of code but they count that against the limit of 2 total data fields.  I asked Garmin about this and this was their reply.

If you load a data field a second time, it does not load the app again. It will call the update function of the existing instance to render into the second view. There aren't any technical reasons why this takes up another ConnectIQ slot when it is done, but User Experience felt that it was better for the slots to behave the way they currently do. The use case you are describing was considered as a part of this decision.

Basically, "tough, that's how it is"

The sensor pairing is the same issue.  Since the watch doesn't support the muscle oxygen profile natively, we need to tell it which Moxy to connect with through the functionality that's available to CIQ data fields.  Data Fields don't allow us to respond to button pushes so we can't create a menu that the user select from.  The best way to set the sensor number is using the settings functionality through Garmin Express.

CIQ Apps are a different thing than CIQ data fields.  A data field extends the functionalty of a native Garmin Activity like Biking or Running or Indoor Biking.  A CIQ App is a whole new Activity and we write almost all of the code that controls the user experience. So we control what is displayed on every screen and what happens when you push each button.  We still use a lot of the underlying native functionality on the watch for things like connecting to a heart rate strap or power meter, but we control what is shown.

CIQ Apps also let us take control of the watch buttons so we can write menus that the user can select from in the App.  This is why you can pair to a Moxy Sensor inside of the CIQ App.

The limit with CIQ Apps is the code size.  Many Garmin devices limit the code size for CIQ apps to 64K so we can only do so much.  Adding menus so the user can customize the display like you can in native activities would take too much memory so we just have a fixed set of data screens.  We can display the Moxy data as many times as we want however.  In Moxy Run and Moxy Cycle, the SmO2 and THb are shown as numbers on the second screen and as a graph on the 4th screen.  The SmO2 alarms work on all 4 screens.

If you have a preferred layout for the data screens, we might be able to make a version of the Moxy Run or Moxy Cycle Apps that is setup that way if it fits within the limits of CIQ.


Development Team Member
Posts: 55
Thanks for looking into this. It makes sense (whether I agree
with it or not).

I don't know exactly what I want, yet. I am at the moment
doing some basic experiments and I don't know yet how I want
the data to be displayed.

I presume that the source code for Moxy apps is not available,
so that I could modify the app myself (I am a programmer).

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