ANT Forum

Hi - I am monitoring incoming data messages in my app, and I am testing against both the ANT+ sensor simulator v1.501 and a Garmin HRM1G belt. Although I am definitely receiving data pages 0, 1, 2, 3 and 4 according to the HRM spec, I don't seem to ever receive any of the "common" data pages that are described in the ANT+ documentation.

My goal is to be able to reliably report on battery life across a range of different ANT+ sensors. It seems like this information is found in the common data pages. Do the HRM sim and Garmin belt support common data pages? If not, what is the recommended method for calculating remaining battery life?

Thanks,
Glenn      

Just FYI: I have two Garmin HRM2 belts (different revisions) and both do NOT report the common data pages.      

I can not see any reference to the common data pages in the HR spec so I don't think you should be expecting them. The same goes for the Bike Speed, Cadence and speed and cadence specs.

From a historical point of view I belive these specs all predate the introduction of the common data pages.      

Not exactly right. These profiles require the sensors to periodically send the common data pages (manufacturer, sw).
Heart rate might be considered a special case, because there are lots of hrm belts out in the field that come from a pre-ANT+ epoch and hence just send a single page type with hrm. Nothing else.      

Clearly some confusion here. Common data pages here I take to mean pages 80, 81 and 82 as defined in the Common Pages seperate document. Background pages in the HR profile would be 1,2 and 3 which are sent periodicaly and Glenn says he is getting them.

Very much the same sort of information in both sets of pages but not the same pages and as I said I don't see any reference to the common pages 80-82 in the HR profile but I do see reference to them in say the bike power profile or any of the newer profiles.      

Bottom line: the Garmin HRM1G does NOT send the 80/81/82 common data pages. So there's no battery monitoring for it.      

Hi All,
Sorry for the confusion you are experiencing regarding HRM and common pages.

In short, HR, SPD, CAD, SPD&CAD; profiles do NOT support ANT+ common pages... below I will explain why:

Heart rate, Bike speed, bike cadence, and combine speed&cadence; are older profiles that predate the concept of typical ANT+ data pages. These profiles were originally created without any concept of a data page number... when we wanted to introduce "pages" we also had to maintain reverse compatibility, so the concept of the "toggle bit" was introduced... this allowed us to create a crude form of data paging - i.e. if you saw the toggle bit, you could interpret byte 0 as a page number.

BUT, you'll notice that certain bytes must ALWAYS follow the "old" format. For example, in HR bytes 4-7 shall always be heart beat event time, heart beat count and computed heart rate. This is so that legacy receivers can always interpret the data even if it is comes from newer HRMs. Since these bytes must always be formatted this way, the HR profile cannot support ANT+ common pages (as they will format bytes 4-7 differently, effectively "breaking" the profile).

it's the same for bike SPD, CAD, SPD&CAD;... but you'll notice the "common page" type data is supported in the other bytes (bytes 1,2,3) of the profile specific pages (i.e. pages 1,2, etc).

hopefully this explanation helps clarify for you!      

Hi - thanks for the helpful background info on the common data pages.

I'm still looking for some way to report battery life levels to our end-users. The HRM Device profile does state that Page 1 returns Cumulative Operating Time. Some of the other sensor profiles also claim to provide this info. Are there any best practices or guidance you can give me on how to extrapolate battery level from cum. operating time in this case? Ideally I would be able to estimate the percent remaining battery life.

Thanks!

Glenn