ANT Forum

Hello,

I've extracted data from my GARMIN HRM using ANT verification tool.
Now, I'm trying to analyse these data with "ANT device profile heart rate monitor" manual.

Data (extract)
xx-B0-B1-B2-B3-B4-B5-B6-B7

...
00-04-00-F0-F4-07-F9-6A-3B (1)
00-04-00-F0-F4-07-F9-6A-3B (2)
00-04-00-F0-F4-07-F9-6A-3B (3)
00-04-00-07-F9-F8-FC-6B-3B (4)
00-84-00-07-F9-F8-FC-6B-3B (5)
00-84-00-07-F9-F8-FC-6B-3B (6)
00-84-00-F8-FC-D8-00-6C-3C (7)
00-84-00-F8-FC-D8-00-6C-3C (8)
00-04-00-F8-FC-D8-00-6C-3C (9)
00-04-00-F8-FC-D8-00-6C-3C (10)
00-04-00-D8-00-CD-04-6D-3C (11)
00-04-00-D8-00-CD-04-6D-3C (12)
...

If I've correctly understood.
Last byte (B7) (3B or 3C) is computed heart rate
byte B6 (6A to 6D) is heart beat count
Bytes B4-B5 give heart beat event time and Bytes B2-B3 give previous heart beat time.

In the manual, i've seen unit is 1/1024 sec

My question (lines 4 to 6):
07-F9 = 2041 /1024 = 1,993 sec ?
F8-FC = 63740/1024 = 64,246 sec ?

These 2 results don't match with heart rate (3C=60 bpm).

Could you give me the method (bit per bit) to calculate heart beat event ?

Thanks for your support,      

please remember byte order is little endian (i.e. LSB first), also ensure you are treating all values as described in the profile (i.e. unsigned values etc).      

That's what I've done (LSB first).
On my example, could you give me your calculated result ? (with details if necessary)

My result
Byte 4, LSB : F8
Byte 5, MSB : FC
F (1111) 8 (1000) -> 11111000
F (1111) C (1100) -> 11111100
F8-FC -> 1111100011111100 = 63740
63740 * 1/1024 = 62,246 sec
Am I right ?      

in your first post, the endianness was incorrect...

decoding the below:

00-04-00-07-F9-F8-FC-6B-3B (4)

previous HB event time = F9 07 = 63 751 s
HB event time = FC F8 = 64760

64760 - 63751 = 1009

1009 / 1024 = ~0.99 seconds which means heart beats ~1 second apart = 60bpm      

Thanks.
Now, I can analyse my R-R intervals :woohoo:      

Not sure about your device, but just a warning that in my experience, it seems that these can be approximate intervals only. Or, alternatively, exact intervals between fictitious (recalculated) events.
See: https://www.thisisant.com/forum/viewthread/6653/
(Please excuse my cross-pollination.)
—DIV

P.S. There is also some interesting discussion at https://www.thisisant.com/forum/viewthread/4233/