Thursday, June 25, 2015

How to get Cadense and speed information using gattool

Last post was a quick "Yay it worked" post. This explains the procedure in more detail.

First use hcitool to scan for your device (activate it in some way so that it powers on first)

Now you know the address, start gattool and connect

$ gatttool -b 00:18:31:E4:D7:89 -I
[   ][00:18:31:E4:D7:89][LE]> connect

Ask for the primary services:

[CON][00:18:31:E4:D7:89][LE]> primary
attr handle: 0x0001, end grp handle: 0x000b uuid: 00001800-0000-1000-8000-00805f9b34fb
attr handle: 0x000c, end grp handle: 0x000f uuid: 00001801-0000-1000-8000-00805f9b34fb
attr handle: 0x0010, end grp handle: 0x001a uuid: 00001816-0000-1000-8000-00805f9b34fb
attr handle: 0x001b, end grp handle: 0x0029 uuid: 0000180a-0000-1000-8000-00805f9b34fb
attr handle: 0x002a, end grp handle: 0xffff uuid: 0000180f-0000-1000-8000-00805f9b34fb

Ask for the characteristics of the handler for the CSCP service (uuid 1816)

[CON][00:18:31:E4:D7:89][LE]> characteristics 0x0010 0x001a
handle: 0x0011, char properties: 0x10, char value handle: 0x0012, uuid: 00002a5b-0000-1000-8000-00805f9b34fb
handle: 0x0014, char properties: 0x02, char value handle: 0x0015, uuid: 00002a5c-0000-1000-8000-00805f9b34fb
handle: 0x0016, char properties: 0x02, char value handle: 0x0017, uuid: 00002a5d-0000-1000-8000-00805f9b34fb
handle: 0x0018, char properties: 0x08, char value handle: 0x0019, uuid: 00002a55-0000-1000-8000-00805f9b34fb

Ask for the character descriptor for the cadence information (uuid 2a5b)

[CON][00:18:31:E4:D7:89][LE]> char-desc 0x0011 0x0013
handle: 0x0011, uuid: 2803
handle: 0x0012, uuid: 2a5b
handle: 0x0013, uuid: 2902

Enable notification by writing 0100 to handle 0x0013.

[CON][00:18:31:E4:D7:89][LE]> char-write-req 0x0013 0100
[CON][00:18:31:E4:D7:89][LE]> Characteristic value was written successfully

You should now start to get notifications from the device
Notification handle = 0x0012 value: 03 ce 00 00 00 82 20 ea 00 be d8 
Notification handle = 0x0012 value: 03 cf 00 00 00 aa dd ea 00 be d8 

See the previous post for an explanation of the data.

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