Hello Xue,
PA_PWR (23h): Control PA Power Control. Input PWR_STEP range: [8 - 28] (-30 to ~8dBm)
Some measurements made with a FRDM-K64 + MCR20A using the Connectivity Test:
| Pwr Step | Board1 | Board2 |
| 8 | -27.29 | -26.87 |
| 9 | -25.75 | -25.09 |
| 10 | -23.92 | -23.23 |
| 11 | -21.91 | -21.28 |
| 12 | -19.72 | -19.06 |
| 13 | -17.76 | -17.15 |
| 14 | -15.92 | -15.31 |
| 15 | -14.00 | -13.41 |
| 16 | -11.98 | -11.48 |
| 17 | -10.13 | -9.67 |
| 18 | -8.27 | -7.80 |
| 19 | -6.45 | -5.45 |
| 20 | -4.57 | -4.16 |
| 21 | -2.75 | -2.34 |
| 22 | -0.86 | -0.53 |
| 23 | 0.86 | 1.18 |
| 24 | 2.67 | 2.84 |
| 25 | 4.28 | 4.45 |
| 26 | 5.74 | 5.88 |
| 27 | 7.00 | 7.09 |
| 28 | 7.94 | 8.02 |
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Indirect_Modem_CCA1_THRESH (22h): Programmable correlation peak threshold, for CCA1 mode (8-bit)
Indirect_Modem_CCA2_THRESH (27h): Programmable correlation peak threshold, for CCA2 mode (8-bit)
I strongly recommend you to take a look at the Kinetis MKW2xD and MCR20A Connectivity Software for you to look at the defaults settings and software implementation.
Set Pwr Level: PhyPlmeSetPwrLevelRequest()
Set CCA Threshold: PhyPpSetCcaThreshold()