[Tinyos-help] compare bit to bit or byte to byte

[Razvan Musaloiu-E.]

Hi!

On Tue, 3 Mar 2009, Sonia Pardo wrote:

> Hi,
>
> Sorry for my explanation but I think is not clear. Let's try again.
>
> I've one mote which send packets in broadcast. On the other side I've three
> motes that receive the packets from first mote. One mote of them is
> connected whit the PC (mote B). I've made a programm that show the data
> content of the received packets  in mote B.
> Maybe mote B receives packets whit errors in data content, then I send a
> message to the others receiver motes and they send mote B the received
> packet again. (I guess that packets of this motes can have others errors in
> data content).
> Now I've three packets in mote B. I can show the data content of the three
> packets in my application. I want to compare bit to bit the data content of
> this three received packets to create a good data content and I only show
> that in my application.
>
> I don't know how to make this comparison bit to bit.
> I make an example:
>
> Transmitter: Send Hello
> Receiver (mote B): Receive Mello
> Receiver C: Receive HeUlo
> Receiver D: Receive HellR
>
> I want to compare bit to bit (Mello, HeUlo and HellR) to create the word
> Hello using majority voting.

I still don't know exactly what you mean by 'bit to bit' but the 
explanations on pages 24-25 from here might be useful:
 	http://www.ti.com/lit/gpn/cc2420
As you can see the bytes are broken into two symbols and each is then 
transmitted as 32 chips. Is this what you were looking for?

--
Razvan ME

> I hope that you understand my explanation better.
>
> Thanks in advanced,
>
> Sonia
>
> 2009/3/3 Razvan Musaloiu-E. <razvanm at cs.jhu.edu>
>
>> Hi!
>>
>> On Tue, 3 Mar 2009, Sonia Pardo wrote:
>>
>>  Dear All,
>>>
>>> We can't use memcmp because this function only say us if the packet is the
>>> same or not.
>>> We would like to compare bit to bit because I want to rebuild the packet.
>>>
>>> For example, we receive three packets from three different motes (But
>>> three
>>> motes send the same information). One of them receives Hello. Other mote
>>> receives Hello too, but the third packet receives Mello. This packet has
>>> errors, but if I compare the three packets bit to bit, I can rebuild the
>>> message of the third packet and I can say that the information of this
>>> packet is Hello too.
>>>
>>> I need a function which compare bit to bit, because I don't know how can I
>>> do this...and I think that memcmp is not valid for this.
>>>
>>> Can anyone help us?
>>>
>>>
>> CC2420 and RF230 are packet-based radios so you don't have access to
>> information about the quality of each bit. CC1000 from mica2 is not
>> packet-based so what you want should be possible there.
>>
>> --
>> Razvan ME
>>
>>
>>  2009/3/2 Janos Sallai <sallai at isis.vanderbilt.edu>
>>>
>>>  How about memcmp in string.h? This is standard C.
>>>>
>>>> Janos
>>>>
>>>> On Mon, Mar 2, 2009 at 11:13 AM, Jordi Pérez <pr.jordi at gmail.com> wrote:
>>>>
>>>>> Dear all,
>>>>>
>>>>> I have a Base Station which receives the same packet from three
>>>>> different
>>>>> motes. The packets must be the same, but maybe, one of them could have
>>>>> some
>>>>> errors. So, I want to make a task which compare bit to bit, or byte to
>>>>> byte,
>>>>> the three packet received to rebuild a new packet without errors.
>>>>>
>>>>> How could I do this task? I don't know how to compare bit to bit (or
>>>>> byte to
>>>>> byte) a received packet. Can you help me please?
>>>>>
>>>>> Thanks in advanced,
>>>>>
>>>>> Jordi
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>