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mvonweis	2010-07-06 , 21:08
Posts: 10 \| Thanked: 5 times \| Joined on Jul 2010	#232

Originally Posted by sampppa

I would support Polar iWL heartrate monitor if someone releases the specification for the bluetooth protocol they use. Currently i can parse heart rate from that data but there are still many things unclear, like does the belt need some kind of wakeup signal every now and then and when connecting the belt with device etc.
I have asked SportsTracker/Polar to open the protocol but no answer yet.

I am not sure if its even legal to use their belt with other applications than SportsTracker especially if we have to reverse engineer their protocol...

Hi,

Just received the Polar WL+ Bluetooth in the mail today and spent the last few hours on studying the protocol. For some reason the belt stops transmitting after 17-20 data points. Here's the hexdump of one data set:

Code:

fe 08 f7 01 f1 00 00 5d
fe 08 f7 02 f1 00 00 5d
fe 08 f7 03 f1 00 00 5d
fe 08 f7 04 f1 00 00 5d
fe 08 f7 05 f1 00 00 5d
fe 08 f7 06 f1 00 00 5d
fe 0a f5 07 f1 3b 03 e4 04 2d
fe 08 f7 08 f1 3a 04 2a
fe 08 f7 09 f1 3a 03 d9
fe 08 f7 0a f1 3b 03 e1
fe 0a f5 0b f1 3c 03 dc 03 a1
fe 08 f7 0c f1 3c 03 b7
fe 08 f7 0d f1 3c 03 d1
fe 0a f5 0e f1 3c 03 b8 03 e1
fe 08 f7 f1 3c 04 1f 
fe 08 f7 00 f1 3c 03 e7
fe 08 f7 01 f1 3c 03 f6
fe 08 f7 02 b1 00 0e 1a

... and there it stops. The belt seems to need some prodding or it goes back to sleep. However sending random characters like space or cr just makes it go silent. Blah.

The second byte seems to define what data the line contains. The lines with fe 08 contain heart rate data: the sixth byte is most likely the heart rate. The fourth byte is a counter (but why is it missing on line 16?).

BTW, I don't see why it wouldn't be legal. Polar also sells the Bluetooth heart rate monitor as an OEM product.

--Martin

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