[Tinyos-help] BaseStationCC2420 does not act as a sniffer: patch

[David Moss]

Here's what I'm seeing, correct me if I'm wrong.

The CC2420BaseStation receives messages over the radio 
through CC2420ActiveMessageC's Receive interface.  This 
interface goes through an address check before delivery:

     if (call AMPacket.isForMe(msg)) {
       return signal Receive.receive[call 
AMPacket.type(msg)](msg, payload, len - CC2420_SIZE);
     } ...

In my local version of CC2420BaseStation, I made a copy of 
CC2420ActiveMessageP.nc into the CC2420BaseStation 
directory and removed this check.

Note that connecting the base station to the snoop 
interface isn't what you want either - then you receive 
every message except messages destined for the base 
station's address.

-David



On Tue, 30 Jan 2007 08:29:03 -0800
  Philip Levis <pal at cs.stanford.edu> wrote:
> On Jan 30, 2007, at 6:40 AM, Alban Hessler wrote:
> 
>> Hi everyone,
>>
>> We have found a small bug in the file CC2240ControlP.nc 
>>for the  
>> BaseStationCC2420 application of T2.
>>
>> In order to be a sniffer (that's what BaseStation is 
>>according to  
>> the readme), the BaseStation should disable the address 
>>filtering  
>> of the CC2420. For that to be done, it must explicitly 
>>set the bit  
>> to 0 in the registry, as the default reset value is 1. 
>>(datasheet  
>> of CC2420, p.65)
>>
>> So the code to set the configuration register in 
>>CC2240ControlP.nc  
>> should be the following:
>>
>> call MDMCTRL0.write( (( 1 << 
>>CC2420_MDMCTRL0_RESERVED_FRAME_MODE ) |
>>       ( 2 << CC2420_MDMCTRL0_CCA_HYST ) |
>>       ( 3 << CC2420_MDMCTRL0_CCA_MOD ) |
>>       ( 1 << CC2420_MDMCTRL0_AUTOCRC ) |
>>       ( 2 << CC2420_MDMCTRL0_PREAMBLE_LENGTH )) &
>>       ~( 1 << CC2420_MDMCTRL0_ADR_DECODE));
>>
>>
>> Notice the added mask at the end of the instruction.
>>
>> Best Regards,
>>
>> Alban Hessler & Evgeny Osipov
>>
> 
> This isn't necessary. It's not a read-modify-write of 
>the register,  just a plain write.
> 
> Phil
> 
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