nRF52832 to Linux L2CAP socket?

RE: nRF52832 to Linux L2CAP socket?

run_ar — Tue, 24 Nov 2020 15:27:57 GMT

Hi,

If you are talking about using a connectionless channel I think that is only supported in BR/EDR and is used for unicasting. For L2CAP connection oriented channels, you first need to have an LE ACL link, then you can configure L2CAP channels on top of that. Meaning it is not possible to setup a L2CAP channel using BTLE without going through the normal advertisement /scanning procedure to create a link.

RE: nRF52832 to Linux L2CAP socket?

kdev — Fri, 20 Nov 2020 16:25:49 GMT

Those examples, unfortunately, do not work. They all require scanning for an advertising device before connecting. Meanwhile, the Linux L2CAP sockets don't seem to advertise or scan at all.

Here's an even more straightforward example of the Linux side of things:

import socket

remoteMac = "00:11:22:33:44:55" # remote device's bluetooth MAC address
port = 4123 # arbitrary port number

isServer = False

s = socket.socket(socket.AF_BLUETOOTH, socket.SOCK_SEQPACKET, socket.BTPROTO_L2CAP)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)

if isServer:
    s.bind( (socket.BDADDR_ANY, port) )
    s.listen()
    s.accept()
else:
    s.connect( (remoteMac, port) )

When running this with isServer = False and monitoring Bluetooth activity with Wireshark, Wireshark doesn't record any scanning commands or results, instead just an HCI connect command:

devzone.nordicsemi.com/.../l2cap_5F00_socket_5F00_connect_5F00_attempt.pcapng

And when running with isServer = True, Wireshark records no Bluetooth activity at all until a remote device initiates a connection. There are no commands to begin advertising or anything similar.

So to connect to this from the nrf52832, how do I tell the SoftDevice to initiate a connection to a remote address directly, without scanning for advertisements that don't exist?

RE: nRF52832 to Linux L2CAP socket?

run_ar — Thu, 19 Nov 2020 12:40:53 GMT

Hi,

I am not familiar with the Linux host api's you are using. But I can mention we have the Object transfer service example, which is using L2CAP:
Object Transfer Service Server Application

Object Transfer Service client Example

This might be useful for you to see how to set up L2CAP with our SD.

RE: nRF52832 to Linux L2CAP socket?

kdev — Tue, 17 Nov 2020 13:09:12 GMT

Edit: In the script, self._port is an arbitrary port number.