Hi Luiz,
>> We are developing a wheelchair that we can controle with a bluetooth
>> gamepad, the XBOX 360 controller to be more precise. It basically works
>> fine but when I remove the battery, I get the disconnect event in the
>> user space around 10 seconds later. That is not acceptable since the
>> wheelchair will keep rolling to potentially dangerous places!
>>
>> I tried to implement a ping mechanism on the bluetooth layer, inspired
>> from bluez sources somewhere:
>> int _socket_fd = socket(PF_BLUETOOTH, SOCK_RAW, BTPROTO_L2CAP);
>> // bind on AF_BLUETOOTH
>> // connect with AF_BLUETOOTH
>>
>> send_cmd->ident = PING_IDENT;
>> send_cmd->len = htobs(PING_DATA_SIZE);
>> send_cmd->code = L2CAP_ECHO_REQ;
>> if (send(_socket_fd, send_buffer, PING_PACKET_SIZE, 0) <= 0) {
>> // ...
>> }
>>
>> It basically works fine except when the signal gets bad. This will get
>> printed by the kernel:
>> [ 859.629431] Bluetooth: hci0 link tx timeout
>> [ 859.635482] Bluetooth: hci0 killing stalled connection 9c:aa:1b:6b:51:c9
>>
>> In that case, I don't get event from the /dev/jsX device but the gamepad
>> seems to still answer to pings??!!
>>
>> Since I haven't found any acceptable workaround and always find the same
>> pages again and again, I'm asking here:
>> * Is it possible to achieve what I want?
>> * Does it make sense that the ping work but the HID layer seems dead?
>> * Any recommendation, pointers?
>
> Id look into adjusting the link supervision timeout instead of
> creating a raw socket, you can use hcitool to do that, neither is
> really great since it require root but at least the supervision
> timeout is something a lot more reliable for this.
we can add an option to L2CAP sockets to adjust the link supervision timeout.
Anyway, these days, I would _not_ use Bluetooth BR/EDR for controlling anything. I would find a Gamepad that utilizes Bluetooth LE and focus on that.
Regards
Marcel
