[Bluez-users] Frequency hopping(channel)

[Bluez-users] Frequency hopping(channel)

[Robert Schmidt]

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Hi,

I have one question to the folks in Bluez group. I saw that we have to specify channel for L2CAP and RFCOMM connections:

struct sockaddr_rc rfcommclient = { 0 };

rfcommclient.rc_channel = channel;

Since Bluetooth uses frequency hopping and hops from one channel to another what is the need to specify this field??

Also, I see that throughout the L2CAP or RFCOMM connections it shows the same PSM value(one we specify for the channel) in the hcidump.

Does that mean no hopping is taking place ??

I am sorry if its a silly question but expecting an answer ??

thanks

robert.


       
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Re: [Bluez-users] Frequency hopping(channel)

[Marcel Holtmann]

Hi Robert,

> I have one question to the folks in Bluez group. I saw that we have to
> specify channel for L2CAP and RFCOMM connections:
> 
> struct sockaddr_rc rfcommclient = { 0 };
> 
> rfcommclient.rc_channel = channel;
> 
> Since Bluetooth uses frequency hopping and hops from one channel to
> another what is the need to specify this field??
> 
> Also, I see that throughout the L2CAP or RFCOMM connections it shows
> the same PSM value(one we specify for the channel) in the hcidump.
> 
> Does that mean no hopping is taking place ??
> 
> I am sorry if its a silly question but expecting an answer ??

you might wanna read the specification again. I know it is big, but you
mixed up a couple of things here. The RFCOMM channels and L2CAP PSMs are
part of the multiplexing (like TCP port numbers). They have nothing to
do with any frequency hopping inside the Bluetooth radio.

Regards

Marcel



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