Hi,
I am experiencing the same issue with TinyOS-2.x.
I think that this is a timing issue. I.e., you are sampling the RSSI
register at a different time then when it is actually used to
generate the metadata (strength field in TinyOS-1.x) for the packet.
You are sampling either after or before the packet is actually
received. Can you please describe when you are sampling the RSSI
register?
Does anyone know if/how it is possible to coordinate the timing so
that the RSSI register gives the same value as is recorded in the
metadata?
Thanks,
Tal
> Hi Philip,
>
> Sorry to bother you, I think your explanation makes sense to me.
> However, if the strength field can give you the RSSI value when
> receiving the packet, why fetching the RSSI register just gives you the
> noise floor. Could you also give me a clue how the value of the strength
> field in TOSMsg is generated based on the RSSI register please? Many
> thanks!
>
> Best regards,
> Ruoshui
>
> Philip Levis wrote:
>>
>> On Jan 15, 2008, at 4:25 AM, Ruoshui Liu wrote:
>>
>>> Dear all,
>>>
>>> I am trying to measure the RSSI value in TinyOS 1.x. However, I have
>>> got two totally different values when I applied two methods to do
>>> this, one is to read the 'strengh field' in the TOSMsg as the MPR/MIB
>>> manual suggests, and the other one is to read the RSSI_VAL register.
>>> I am wondering why I have obtained such different values, for example,
>>>
>>> before adding the offset value (-45): the reading from the 'strengh
>>> field' is -20; the reading from the RSSI_VAL register is -53;
>>> after adding the offset value (-45): the reading from the 'strengh
>>> field' is - 65; the reading from the RSSI_VAL register is -98.
>>>
>>> I am really confused, could anyone help me with the reason for this
>>> pleaes?
>>>
>>
>>
>> The strength field is the RSSI of a received packet. If you read the
>> RSSI register, then you might be sampling the RSSI when you are *not*
>> receiving a packet, at which point it is the hardware noise floor. -98
>> dBm is a reasonable hardware noise floor for a cc2420-based node.
>>
>> Phil
>
> _______________________________________________
> Tinyos-help mailing list
> [email protected]
> https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
>
_______________________________________________
Tinyos-help mailing list
[email protected]
https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
