[Tinyos-help] Output Power levels CC2420

Alexander Becher becher at i4.informatik.rwth-aachen.de
Wed Feb 27 07:37:09 PST 2008


* Rodolfo de Paz Alberola:
>I am extending a micaz software emulator to support CC2420 and testing
>it with tinyos-2.x. 
>
>When dealing with the Output Power Levels that cc2420 support in the
>TXCTRL.PA_LEVEL register, I found the problem that in data sheet they
>don't indicate all dBm values for the different 32 values, the only
>indicate the following:
>
>PA_LEVEL	Pow (dBm)
>31		0
>27		-1
>23		-3
>19		-5
>15		-7
>11		-10
>7		-15	
>3		-25
>
>However using the cc2420 driver of tinyos-2.x I can set 32 different
>values, so I would like to know what happend if somebody set a for
>example PA_LEVEL = 21, which Pow(dBm) value should give the cc2420
>radiochip? anybody has the completely correspondence between levels and
>dBm? or even much better a equation to calculate them?

I once set PA_LEVEL = 5 accidentally in a radio measurement. Reception
quality was between setting 7 and 3, so it was apparently sending at
-20 dBm or so.

If you plot the above values, you get what looks like a square root
curve. Maybe it's OK to interpolate the other settings from a fitted
equation like P = a*sqrt(b*PA_LEVEL)+c.

Regards,
Alexander


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