Bluetooth LE Signal Strength Linux

Question

Hello is there any way to get the signal strength of near by bluetooth le devises in linux? Or any good libraries for nodejs, php or mono (I do know some c++ or python but would prefer to say away from them) if a tool does not exisst but would be fairly easy to write.

Solution 1

On Linux, the way to do this is with the hcitool command. However, you have to be connected to get the rssi of a device. If you want to achieve this from the command line, try:

#hcitool rssi AA:BB:CC:DD:EE:FF

If you want to see the actual C code to achieve this, take a look at the bluez tools/hcitool.c file, under the cmd_rssi function.

static void cmd_rssi(int dev_id, int argc, char **argv)
{
    ...
}

---

For Bluetooth Low Energy, I only know one way to do this, and that is using the #btmon command. Run btmon in the background then scan for Bluetooth Low Energy devices:

#./btmon &
# hcitool lescan

The results displayed on the monitor should be similar to this:

> HCI Event: LE Meta Event (0x3e) plen 12                                                                                  
      LE Advertising Report (0x02)
        Num reports: 1
        Event type: Scan response - SCAN_RSP (0x04)
        Address type: Public (0x00)
        Address: AA:BB:CC:DD:EE:FF (<Vendor Name>)
        Data length: 0
        ***RSSI: -34 dBm (0xde)***
AA:BB:CC:DD:EE:FF <Device Name>

Note that when using btmon you do not have to connect to get the rssi of a BLE device.

Solution 2

No need to connect when using btmgmt

$ sudo btmgmt find

Discovery started
hci0 type 7 discovering on
hci0 dev_found: 50:8C:FD:99:0A:EC type LE Random rssi -80 flags 0x0000 
AD flags 0x06 
eir_len 23
…

The relative signal strength indicator is rssi -80, but the list is much longer containing more information about this and other devices.

To spy on your Bluetooth neighbourhood showing only unique MAC addresses with their strongest RSSI, run the following command:

$ sudo btmgmt find |grep rssi |sort -n |uniq -w 33

hci0 dev_found: 40:43:42:B3:71:11 type LE Random rssi -53 flags 0x0000 
hci0 dev_found: 44:DA:5F:EA:C6:CF type LE Random rssi -78 flags 0x0000 
hci0 dev_found: 7F:7D:08:6B:E0:37 type LE Random rssi -74 flags 0x0000 
hci0 dev_found: A4:58:0F:21:A1:8C type BR/EDR rssi -79 flags 0x0000

Solution 3

You can use a combination of:

sudo hcitool lescan --duplicates & ;
sudo hcidump --raw 

that will provide you the raw dump of all the bluetooth packets which contain all relevant information you must be interested in such as : UUID, Major, Minor, RSSI, TxPower. You will have to run some kind of script to parse and filter LE packets and make them into readable form.

One of the scripts written with Bash and S editor was provided by jjnebaker here with the problem and solution discussed here

The Other option is to use PyBluez using the example code here But you might find the solution provided by Switchdoc labs useful according to your needs as well. here

Solution 4

This works for c language, but has an error when casting the bytes that have the information about de rssi signal. https://github.com/glock45/intel-edison-playground/blob/master/scan.c

this line 121:

printf("%s - RSSI %d\n", addr, (**char**)info->data[info->length]);

should be:

printf("%s - RSSI %d\n", addr, (**int8_t**)info->data[info->length]);

I found these by looking inside bluez-version/monitor/*.c, where btmon program is. You can see the data types and structs, hcidump.c is very useful and packets.c, and main.c too, but there are many to learn about the hci sockets.

Solution 5

i found several solutions, but most were too slow for my needs to use as a tracking function.

check out https://github.com/abandonware/noble containing some examples.

my standalone scanner is also based on abandonware's module and can be found here: https://github.com/efeuentertainment/BLE-continuous-RSSI-scan

node index.js BLEMAC

continuously lists the RSSI with an update frequency of about 2 per second / depending on BLE device.

also fast updates based on bash is:

sudo hcitool lescan --duplicates &

combined with one of the following lines: continuous updates

sudo hcidump | grep "E6:4E:57:09:74:E4" -A 4
sudo btmon | grep "E6:4E:57:09:74:E4" -A 7

only the next received update

sudo hcidump | grep -m 1 "E6:4E:57:09:74:E4" -A 4 | grep "RSSI"
sudo btmon | grep -m 1 "E6:4E:57:09:74:E4" -A 7 | grep "RSSI"

hope that helps. it's an old thread but my search engine lead me here anyway.

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Comments

[Tim Holum]

hcitool rssi Seems to only be for regular bluetooth not bluetooth le, I get "Get connection info failed: No such file or directory" when I try even when connected ( for bluetooth le you connect by hcitool lecc [MAC] not the regular hcitool cc [MAC],

[Youssif Saeed]

Tagged the question with bluetooth-lowenergy because I missed the le part :) Have you tried #hcidump? I've read that you can use it to read rssi value of Low Energy devices but I have no devices with me to test that.

[Youssif Saeed]

Edited the question to include the Bluetooth Low Energy part. I tried #hcidump and it didn't work for me, but #btmon worked just fine.

[Md Mahbubur Rahman]

What is the meaning of "plen 12" in the first line of BLE scan " > HCI Event: LE Meta Event (0x3e) plen 12" ?

[JerzySBG]

Fastest scanner I found. Tested on Linux Mint with gcc 5.5.0 on Asus dongle (connected to PC) and it reads fine with cast to "(char)".

[Mr. Panda]

If BLE devices are connected, you can't find RSSI with this way.