Testing protocol stack with OsmocomBB (cheap way)

Drasko DRASKOVIC drasko.draskovic at gmail.com
Sun May 29 23:58:37 UTC 2011

On Mon, May 30, 2011 at 1:22 AM, Sylvain Munaut <246tnt at gmail.com> wrote:
> Hi,
>> Now, I understand that osmocon can be used to load layer1 into phones
>> RAM, so that this code turns on Calypso and communicate with DSP with
>> AT commands.
> ... there is no AT commands anywhere ...
Oh... I thought that firmware on ARM was communicating with DSP via AT
messages... How does it control DSP then? I see that data is exchanged
via shared memory in SRAM, but how does Calypso call DSP interface to
do some processing ?

>> (http://en.wikipedia.org/wiki/Universal_Software_Radio_Peripheral)
>> FPGA motherboard with both RX and TX doughterboards is needed, which
>> can go up to 1k eur (too expensive for a hobbist).
> Depends how motivated the hobbyist is ... I know _plenty_ of people
> that pay _way_ more for their hobby.

I agree with you, but imagine someone who is looking around from the
distance at one very interesting project. Fistly, I am not network
stack engineer, but more attracted by the platform and system. But I'd
like to get my feet wet, and not ready to throw 1k eur on the
equipment I do not know at all. I'd rather try things around, get a
feel and then, as I get involved, collect some material. You might
disagree with me, but I think that for open source projects related to
HW price is very important - keeping the price very low helps more
people get involved in the project in the first place.

Here, I ended up with telephone that can not do practicaly anything -
can not receive nor transmit packets. Or am I wrong ? Can I use some
data from public network, just to see some packets flow, so I can at
least get some feel ?

>  Or recreational shooting ... guns cost a lot and each clip
> fired is literally 5$ up in smoke.
This does not surprise me much, world is full of morons. On the other
side of the planet someone is litteraly dying for this $5.

> People keep saying the USRP is very expensive ... well, not so much really.
I can agree on this, it is not so expensive. But I explained position,
so at this moment I am reconsidering solutions.

>> Is there some open source FPGA that can be used for this purpose?
> The USRP and board schematics can be found ... and the sw is all opensource.
When you say SW, I guess you mean some host applications ?

What I was talking about is available HDL code that I can flash into
my (eventually modified) FPGA board.

> You're free to build one yourself. Of course it's gonna cost you way
> more than buying one.

I would more opt for idea of open source VHDL or Verilog code that can
be flashed into non-expensive FPGA development boards (some Spartan or
Altera or something) and open source schematics for additional
hardware that can be soldered around to have signals coming.

At this point I am not interested at full-blown BTS, but some minimal
stuff that can send something via radio link that would be captured by
the phone and transmitted via stack towards Wireshark on the host.
Just the basic test. I do not need it for GSM protocol reserach,
rather something that can give feel and usability to the OsmocomBB
project, before someone has enough informations and idea to buy USRP.


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