CC1021-RTR1 datasheet(31/91 Pages) TI1

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Not Recommended for New Designs NRND

CC1021

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SWRS045D – JANUARY 2006 – REVISED JANUARY 2015

For best RSSI accuracy, use AGC_AVG(1:0] = 11 during image rejection calibration (RSSI value is

averaged over 16 filter output samples). The RSSI register update rate then equals the receiver channel

bandwidth (set in FILTER register) divided by 8, as the filter output rate is twice the receiver channel

bandwidth. This gives the minimum waiting time between RSSI register reads (0.5 ms is used below). TI

recommends the following image calibration procedure:

1. Define 3 variables: XP = 0, XG = 0 and DX = 64. Go to step 3.

2. Set DX = DX/2.

3. Write XG to GAIN_COMP register.

If XP + 2 × DX < 127, then

write XP + 2 × DX to PHASE_COMP register

else

write 127 to PHASE_COMP register.

4. Wait at least 3 ms. Measure signal strength Y4 as filtered average of 8 reads from RSSI register with

0.5 ms of delay between each RSSI read.

5. Write XP+DX to PHASE_COMP register.

6. Wait at least 3 ms. Measure signal strength Y3 as filtered average of 8 reads from RSSI register with

0.5 ms of delay between each RSSI read.

7. Write XP to PHASE_COMP register.

8. Wait at least 3 ms. Measure signal strength Y2 as filtered average of 8 reads from RSSI register with

0.5 ms of delay between each RSSI read.

9. Write XP-DX to PHASE_COMP register.

10. Wait at least 3 ms. Measure signal strength Y1 as filtered average of 8 reads from RSSI register with

0.5 ms of delay between each RSSI read.

11. Write XP – 2 × DX to PHASE_COMP register.

12. Wait at least 3 ms. Measure signal strength Y0 as filtered average of 8 reads from RSSI register with

0.5 ms of delay between each RSSI read.

13. Set AP = 2 × (Y0 – Y2 + Y4) – (Y1 + Y3).

14.

If AP > 0 then

set DP = ROUND ( 7 × DX × (2 × (Y0 – Y4) + Y1 – Y3) / (10 × AP))

else

if Y0 + Y1 > Y3 + Y4 then

set DP = DX

else

set DP = –DX.

15.

If DP > DX then

set DP = DX

else

if DP < –DX then set DP = –DX.

16. Set XP = XP + DP.

17. Write XP to PHASE_COMP register.

18.

If XG + 2 × DX < 127 then

write XG + 2 × DX to GAIN_COMP register

else

write 127 to GAIN_COMP register.

19. Wait at least 3 ms. Measure signal strength Y4 as filtered average of 8 reads from RSSI register with

0.5 ms of delay between each RSSI read.

20. Write XG + DX to GAIN_COMP register.

21. Wait at least 3 ms. Measure signal strength Y3 as filtered average of 8 reads from RSSI register with

0.5 ms of delay between each RSSI read.

22. Write XG to GAIN_COMP register.

23. Wait at least 3 ms. Measure signal strength Y2 as filtered average of 8 reads from RSSI register with

0.5 ms of delay between each RSSI read.

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CC1021-RTR1 Datasheet(PDF) 31 Page - Texas Instruments

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