[Bluez-users] rfcomm device blocking/data available behaviour

[Bluez-users] rfcomm device blocking/data available behaviour

[Dave Marples]

Folks,

I've got a problem using rfcomm to a generic BT device (actually a SE 
K750i phone, but that's just what I'm using for an example).  It looks 
to me like a bug in the rfcomm/socket interface, but what do I know?

The problem seems to be that blocking/select on a rfcomm serial port 
isn't working correctly. This is using Ubuntu Dapper (latest release) 
and I've checked the bluetooth/rfcomm directory against patch 2.6.16-mh3 
to ensure that all of the current changes are in there, and they are (in 
fact, only core.c has changed, and that's mostly beautification).

The easiest way to create the problem is as follows;

1) In /etc/bluetooth/rfcomm.conf establish a connection to the phone;

rfcomm3 {
   bind yes;
   # Bluetooth address of the device
   device xx:xx:xx:xx:xx:xx;
   # RFCOMM channel for the connection
   channel    1;
   # Description of the connection
   comment "K750i";
}

2) ...then cat /dev/rfcomm3

Obviously, at this point nothing happens.
3) _RING_ the phone

The output from the 'cat' job goes crazy, and never finishes.

Another way to create the problem  is the following (using python);

fd=open("/dev/rfcomm3","r+")
fd.write("ATZ\n")
while 1:
   c=fd.read(1)
   print "Got",len(c),"Detail:",ord(c),c

Can anyone help?  I'm stuck here....it's quite possible I'm doing 
something _really_ silly, but I need someone to hold a mirror up to be 
able to see that...

Regards

DAVE



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Re: [Bluez-users] rfcomm device blocking/data available behaviour

[Dave Marples]

Folks,
Replying to myself here, but moving over to the python library, the 
following code _works_;

import bluetooth

s=bluetooth.BluetoothSocket( bluetooth.RFCOMM )
s.connect(("xx:xx:xx:xx:xx:xx",1))
s.send('ATZ\r')
while 1:
    c=s.recv(1)
    print "Got",len(c),"Detail:",ord(c),c

...so, I can only conclude that it's something to do with the device 
emulation side of things.  Hope this is helpful to someone.

Regards

DAVE

Dave Marples wrote:
> Folks,
>
> I've got a problem using rfcomm to a generic BT device (actually a SE 
> K750i phone, but that's just what I'm using for an example).  It looks 
> to me like a bug in the rfcomm/socket interface, but what do I know?
>
> The problem seems to be that blocking/select on a rfcomm serial port 
> isn't working correctly. This is using Ubuntu Dapper (latest release) 
> and I've checked the bluetooth/rfcomm directory against patch 2.6.16-mh3 
> to ensure that all of the current changes are in there, and they are (in 
> fact, only core.c has changed, and that's mostly beautification).
>
> The easiest way to create the problem is as follows;
>
> 1) In /etc/bluetooth/rfcomm.conf establish a connection to the phone;
>
> rfcomm3 {
>    bind yes;
>    # Bluetooth address of the device
>    device xx:xx:xx:xx:xx:xx;
>    # RFCOMM channel for the connection
>    channel    1;
>    # Description of the connection
>    comment "K750i";
> }
>
> 2) ...then cat /dev/rfcomm3
>
> Obviously, at this point nothing happens.
> 3) _RING_ the phone
>
> The output from the 'cat' job goes crazy, and never finishes.
>
> Another way to create the problem  is the following (using python);
>
> fd=open("/dev/rfcomm3","r+")
> fd.write("ATZ\n")
> while 1:
>    c=fd.read(1)
>    print "Got",len(c),"Detail:",ord(c),c
>
> Can anyone help?  I'm stuck here....it's quite possible I'm doing 
> something _really_ silly, but I need someone to hold a mirror up to be 
> able to see that...
>
> Regards
>
> DAVE
>
>
>
> _______________________________________________
> Bluez-users mailing list
> Bluez-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/bluez-users
>   



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Re: [Bluez-users] rfcomm device blocking/data available behaviour

[Marcel Holtmann]

Hi Dave,

> Replying to myself here, but moving over to the python library, the 
> following code _works_;
> 
> import bluetooth
> 
> s=bluetooth.BluetoothSocket( bluetooth.RFCOMM )
> s.connect(("xx:xx:xx:xx:xx:xx",1))
> s.send('ATZ\r')
> while 1:
>     c=s.recv(1)
>     print "Got",len(c),"Detail:",ord(c),c
> 
> ...so, I can only conclude that it's something to do with the device 
> emulation side of things.  Hope this is helpful to someone.

the RFCOMM TTY devices are not in raw mode by default. You need to do
that by yourself. However every application should now what's the best
mode to use the device and cat is simply too dumb.

Regards

Marcel




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