hcitool lescan shows I/O error

Question

I'm trying to do a lescan using hcitool on the raspberry pi.

The command prints out

Set scan parameters failed: Input/output error. 

I'm not sure, what exactly happens here. My iPhone is advertising here.

I'm using a BLE dongle from IOGear.

However, if I restart my machine, it shows the a MAC address after I issue the lescan command, and starts showing the same error after I issue the lescan command a couple of more times. Is it like, the lescan command cannot be issued more than once?

Answer 1

sudo hcitool lescan

Just use sudo & will scan

Answer 2

It is possible, that HCI is currently in use. In my case I must stop Node-Red and it works. So take care, that the HCI isn't in use.

Restart the HCI is a way, to solve the problem temporarily, but it doesn't solve the problem right.

Answer 3

Upgrading to bluez v5.43 fixed this for me.

To upgrade to the newest bluez, you need to do a "manual" installation (not apt-get), downloading from the bluez website. I recommend this video walkthrough if you are new installing packages or need help.

After installing the latest bluez, I had to run a couple commands before it worked.

1. systemctl daemon-reload : Restarts the system daemon.

2. sudo service bluetooth restart : Restarts the Bluetooth service.

3. sudo hciconfig hci0 up : This was needed for my Raspberry Pi 3, with the built-in BT found at hci0.

After these commands, sudo hcitool lescan and its variants all seem to work.

Answer 4

I had the same error with hcitool, while bluetoothctl worked just fine. Then I ran across this article stating that all "tools using raw socket shall be considered deprecated" (hcitool, hcicfg, etc.).

So maybe just open bluetoothctl and issue a scan on command.

Answer 5

To those finding this question now, it is fixed as of Bluez v5.41. All you need to to is download and install. You can download the lastest version from http://www.bluez.org/download/.

Answer 6

What worked for me though is opening up the Bluetooth settings on my Ubuntu and manually removing the unused devices. Immediately lescan started working.