Re: [Bluez-devel] Question on using HCIDUMP to interpret data monitored from an uart

[Marcel Holtmann <marcel@holtmann.org>]

Hi Han,

> I have a question about using hcidump to translate serial logged HCI
> communication to readable form.
>  
> The situation is this, I have 8 embedded devices of which 1 is the
> master and the other 7 are slave devices in a piconet and they
> communicate to each other via RFCOMM. The master sets up a connection
> to all 7 slaves in the beginning of the communication process and then
> communicates with all 7. But there is a problem that the communication
> stops after some time and we want to check what is going on.
> The embedded devices are Linux based systems with a CSR bluecore, the
> main processor communicates with the Bluecore via a serial link
> running the BCSP protocol. The Bluecore is running the lower layers of
> the stack and talking HCI to the host processor which is running
> BlueZ.
>  
> What we have now to monitor communications is one device that has the
> serial connection between Bluecore and Linux host processor routed to
> 2 external serial ports for monitoring. So it is possible to capture
> all communications between the Bluecore and the Linux host processor.
> We already have software that strips the BCSP protocol and saves the
> raw data in the format of a hcidump save file, but there is some extra
> data in the packets stored in the file that we don't know where it
> comes from, but is required by hcidump to translate the data into
> readable form. We have already found out about the time-stamp and
> direction fields, but there is other data that we suspect is state
> information added by the BlueZ stack and we don't know what that is.
>  
> Is it possible to somehow feed the data from the serial port to
> hcidump and have hcidump translate that data to readable form or is
> there some extra data reaquired that is generated by the BlueZ stack ?

this is possible and you can use the hcidump native format or the
BTSnoop format. Look at the hcidump source code and you will find the
header and format information right there. In general it is a H4 stream
with additional timestamp and direction information.
 
> BTW. it is not possible to run hcidump on the embedded device, because
> there is no way to create files on it and the CPU is to slow to handle
> the extra load (probably).

You can make hcidump to send the stream over TCP and then decode or
store it on another machine.

Regards

Marcel




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