Cannot connect to BLE device on Raspberry Pi

Question

I'm trying to connect to a BLE device (Heart rate sensor, Polar H7), on a Raspberry Pi 2. I use the last version of bluez (5.35) found here: http://www.bluez.org/download/ But when I'm trying to connect using gatttool, I always have "connection refused" error.

Here is what I do :

pi@raspberrypi ~ $ sudo su
root@raspberrypi:/home/pi# hciconfig dev
hci0: Type: BR/EDR Bus: USB
 BD Address: 5C:F3:70:69:54:3D ACL MTU: 1021:8 SCO MTU: 64:1
 DOWN
 RX bytes:616 acl:0 sco:0 events:34 errors:0
 TX bytes:380 acl:0 sco:0 commands:34 errors:0
root@raspberrypi:/home/pi# hciconfig dev up
root@raspberrypi:/home/pi# hcitool lescan
LE Scan ...
00:22:D0:6D:E0:E6 (unknown)
00:22:D0:6D:E0:E6 Polar H7 6DE0E61C
^Croot@raspberrypi:/home/pi# hcitool lecc 00:22:D0:6D:E0:E6
Connection handle 64
root@raspberrypi:/home/pi# gatttool -b 00:22:D0:6D:E0:E6 -I
[00:22:D0:6D:E0:E6][LE]> connect
Attempting to connect to 00:22:D0:6D:E0:E6
Error connect: Connection refused (111)
[00:22:D0:6D:E0:E6][LE]> 

I tried to follow this topic: BLE gatttool cannot connect even though device is discoverable with hcitool lescan but it did not work for me.

• Zimano: If you have Bluez, why not just use bluetoothctl?

Answer 1

I was able to connect via Bluetooth from Raspberry to my Android device using gatttool after setting the LE address type to random with the -t random argument, i.e. :

sudo gatttool -t random -b DD:9D:0B:43:A1:77 -I
connect

---

From gatttool man

--t, ---addr-type=[public | random] 
# Set LE address type. Default: public

---

USAGE gatttool [OPTION...]
 Help Options:
 -h, --help Show help options
 -h, --help Show help options
 --help-all Show all help options
 --help-gatt Show all GATT commands
 --help-params Show all Primary Services/Characteristics
 arguments
 --help-char-read-write Show all Characteristics Value/Descriptor
 Read/Write arguments
 Application Options:
 --i, ---adapter=hciX Specify local adapter interface
 --b, ---device=MAC Specify remote Bluetooth address
 --t, ---addr-type=[public | random] Set LE address type. Default: public
 --m, ---mtu=MTU Specify the MTU size
 --p, ---psm=PSM Specify the PSM for GATT/ATT over BR/EDR
 --l, ---sec-level=[low | medium | high] Set security level. Default: low
 --I, ---interactive Use interactive mode

• Panossa: What if someone did all of the things in this post? Turning on BLE, using -t random and the connection is still refused? Asking for a friend.

Answer 2

By default GATT is not enable. Add the below lines to /etc/bluetooth/main.conf

EnableLE = true // Enable Low Energy support. Default is false.
AttributeServer = true // Enable the GATT attribute server. Default is false.

Answer 3

I got it running with:

btmgmt le on

Answer 4

I had to disable the plugin pnat in /etc/bluetooth/main.conf -> DisablePlugins=pnat. I read that it's unstable, but I don't know much about this plugin.

• Andrea Lazzarotto: Good grief, this is the most underrated answer ever! This solved every problem I had on a Raspbian system, after days of other attempts.

Answer 5

Fixed the connection refused (111) issue in my raspberry pi 3B running raspbian buster by Updating/installing BlueZ via apt-get

> sudo apt-get install --no-install-recommends bluetooth

and re running

> sudo gatttool -t random -b E9:1C:89:B7:16:F9 -I

Answer 6

If you are still wondering why the random from @Pedro Lobito's answer worked. I have gone through the code and this what I found.

​-t ​(Addr:Type: Set LE Address Type) 

Public | random 
Default: Public

A random or static address is a 48-bit randomly generated address and shall meet the following requirements:

• The two most significant bits of the static address shall be equal to ‘1’

• All bits of the random part of the static address shall not be equal to ‘1’

• All bits of the random part of the static address shall not be equal to ‘0’

(Source)

• Pedro Lobito: A link as comment on my answer would be more appropriate than creating a new answer.
• icc97: This also still doesn't explain why random works

Answer 7

You could try to use gatttool -b 00:22:D0:6D:E0:E6 -I and then connect, just after discovering the MAC without connecting before with hcitool lecc 00:22:D0:6D:E0:E6