CC2431

SWRS034

Page 9 of 14

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85

90

95

10*log10(distance)

Path Loss vs. log-distance for source 0x85, Z=2.1082. A=42.4103, n=2.9773

Figure 2: Path loss vs. log distance

2.1.2.1.4 RSSI Values

The

RSSI

values

are

the

RSSI

measurements corresponding to the set of

reference coordinates. The RSSI values

are within the interval [-40 dBm, -95 dBm]

with precision 0.5 dBm. The negative sign

is removed in the value written. As an

example, in the case where the value

RSSI = -50.35 dB, this would be written

into the location engine as 50.5.

Note that a value of 0.0 must be written as

RSSI

value

for

unused

reference

coordinates. The engine will not function

correctly if only some of the parameters

are loaded.

2.1.2.2 Loading Parameters

All measured parameters are loaded into

the RF register

to

register bit

that a set of measured parameters are

being written. Once the parameter load

process commences (

LOCENG.PARLD

=1), all ten parameters must be written.

The measured parameters must be written

in the order [A, n, rssi0, rssi1, … rssi7] to

the

Once the

parameter

load

process

commences

(

LOCENG.PARLD

=1)

it

must

be

completed. Eight RSSI values must be

written, so any unused slots must be

written as zeros. After all ten parameters

have been written, a 0 must be written to

the register bit

2.1.3

Location Estimation

The estimated location coordinates are

given in meters in the interval [0.0, 63.5]

with precision 0.5 m. The data format uses

the LSB bit as the fractional part.

When

reference

coordinates

and

measured parameters have been loaded,

the location estimate is calculated by

writing 1 to the

The estimated coordinates can be read

from the

1200 system clock cycles (16/32 MHz)

after

Location Engine does not produce any

interrupt requests.

The estimated coordinates remain valid in

the