ANT Forum

I was happy to find that Tech Note! What I find curious is that the Ant+ HRM Device Profile doc describes the use of Pages 0-4, and the operation of the page toggle bit (etc.).

Does that not apply for all HRMs?

What is described in the Tech Note does not get into data pages - just raw data. This appears to be consistent with Saris Cycle Ops heart rate strap that I am trying to receive data from.

I am new to the Ant+ world, so I have a feeling I am missing something in the terminology, or some other documentation.      

Legacy heart rate sensors do not use the ANT+ paging systems... as a result, the toggle bit was introduced in order to differentiate between newer HRM's that do use ANT+ pages, and older HRM's that don't.

Older/legacy HRM's only transmit a single data "page", of which the upper 4 bytes are undefined. As a result, their contents are random. In order to use data page numbers, the toggle bit provides a mechanism for indicating the use of page numbers...

i.e. if the toggle bit alternates between 0 and 1 in the pattern set out in the device profile... then the remaining 7 bits may be interpreted as the page number... if the toggle bit does NOT alternate between 0 and 1 at the set pattern... then the data comes from an older HRM and only the lower 4 bytes may be interpreted...