CC113LRGPR datasheet(33/87 Pages) TI2

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Input Power (dBm)

1.2 kBaud

38.4 kBaud

250 kBaud

500 kBaud

C012

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±110

±100

±90

±80

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±60

±50

±40

±30

±20

±10

±120±110±100 ±90 ±80 ±70 ±60 ±50 ±40 ±30 ±20 ±10

Input Power (dBm)

1.2 kBaud

38.4 kBaud

250 kBaud

500 kBaud

C011

CC113L

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SWRS108B – MAY 2011 – REVISED JUNE 2014

The RSSI value read from the RSSI status register is a 2s complement number. The following procedure

can be used to convert the RSSI reading to an absolute power level (RSSI_dBm).

1. Read the RSSI status register

2. Convert the reading from a hexadecimal number to a decimal number (RSSI_dec)

3. If RSSI_dec

≥ 128 then RSSI_dBm = (RSSI_dec - 256)/2 – RSSI_offset

4. Else if RSSI_dec < 128 then RSSI_dBm = (RSSI_dec)/2 – RSSI_offset

Table 5-9 gives typical values for the RSSI_offset. Figure 5-9 and Figure 5-10 show typical plots of RSSI

readings as a function of input power level for different data rates.

Table 5-9. Typical RSSI_offset Values

Data rate [kBaud]

RSSI_offset [dB], 433 MHz

RSSI_offset [dB], 868 MHz

1.2

38.4

250

500

spacer

Figure 5-10. Typical RSSI Value Versus Input Power Level for

Figure 5-9. Typical RSSI Value Versus Input Power Level for

Different Data Rates at 868 MHz

Different Data Rates at 433 MHz

5.12.3 Carrier Sense (CS)

Carrier sense (CS) is used as a sync word qualifier and can be asserted based on two conditions which

can be individually adjusted:

•

CS is asserted when the RSSI is above a programmable absolute threshold, and deasserted when

RSSI is below the same threshold (with hysteresis). See more in Section 5.12.3.1.

•

CS is asserted when the RSSI has increased with a programmable number of dB from one RSSI

sample to the next, and de-asserted when RSSI has decreased with the same number of dB. This

setting is not dependent on the absolute signal level and is thus useful to detect signals in

environments with time varying noise floor. See more in Section 5.12.3.2.

Carrier sense can be used as a sync word qualifier that requires the signal level to be higher than the

threshold for a sync word search to be performed and is set by setting MDMCFG2. The carrier sense

signal can be observed on one of the GDO pins by setting IOCFGx.GDOx_CFG=14 and in the status

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