S2-LP datasheet(32/90 Pages) STMICROELECTRONICS

32 / 90 page

Block description

S2-LP

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DocID029944 Rev 1

Furthermore, since the payload is normally arranged in bytes, the arrangement can change

the mapping for both 2-(G)FSK and 4-(G)FSK modulations, by using the CONST_MAP

(register MOD1), in the following way:

Table 38: Constellation mapping 2-(G)FSK

Format

Symbol

CONST_MAP coding

2-(G)FSK

-FDEV

+FDEV

-FDEV

Table 39: Constellation mapping 4-(G)FSK

Format

Symbol

CONST_MAP coding

4-(G)FSK

-FDEV/3

-FDEV

+FDEV/3

+FDEV

-FDEV

-FDEV/3

+FDEV

+FDEV/3

+FDEV

-FDEV/3

-FDEV

+FDEV

+FDEV/3

-FDEV

-FDEV/3

Furthermore, in the 4-(G)FSK it is also possible to swap the symbols using the

4FSK_SYM_SWAP field (register PCKTCTRL3) as follows:

When 4FSK_SYM_SWAP = 0: {

S0 =< b7b6 >

S1 =< b5b4 >

S2 =< b3b2 >

S3 =< b1b0 >

When 4FSK_SYM_SWAP = 1: {

S0 =< b6b7 >

S1 =< b4b5 >

S2 =< b2b3 >

S3 =< b0b1 >

5.4.1.1

Gaussian shaping

In 2-GFSK or 4-GFSK mode, the Gaussian filter BT product can be set by using the

The Gaussian filtering is implemented by poly-phase filtering with eight taps per symbol

time. In order to further smooth the filter shape and improve spectral shaping, the output of

the filter can be linearly interpolated by setting the register MOD_INTERP_EN.

A mathematical interpolation factor is applied at each sample of the Gaussian filter output.

This factor is 64 for data rates corresponding to DATA_RATE_E < 5, it is automatically

scaled as

2��_��_��−5

for 5 ≤ DATA_RATE_E < 11 and it is automatically disabled for

DATA_RATE_E = 11.

The actual interpolation factor achieved may be limited by the minimal frequency

resolution of the frequency synthesizer.

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