Question

What are the valid values for txPower?

Answer

On EM2xx platform, valid PHY power range of the radio is -43 dBm to 3 dBm. Any integer power level that falls within this range will be rounded to the nearest supported setting.

Supported Settings: -43, -26, -20, -17, -14, -12, -11, -9, -8, -7, -6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5

Note: txPower values 4 and 5 dBm are available only in boost mode (which will increase power consumption significantly, thus reducing battery life).

On EM35x platform, valid PHY power range of the radio is -43 dBm to 8 dBm. Any integer power level that falls within this range will be rounded down to nearest supported setting

Supported Settings: -43, -26, -20, -17, -14, -12, -11, -9, -8, -7, -6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8

Note: txPower values 4 through 8 dBm are available only in boost mode (which will increase power consumption significantly, thus reducing battery life).

The EFR32 families of chips each come equipped with three Power Amplifiers (PAs):

• EFR32xG1x
  • A high-power * 2.4 GHz PA (for power 20 dBm and lower)**
  • A low-power 2.4 GHz PA (for power 0 dBm and lower)
  • A Sub-GHz PA**

• EFR32xG21
  • A high-power 2.4 GHz PA (for power 20 dBm and lower)**
  • A medium-power 2.4 GHz PA (for power 10 dBm and lower)
  • A low-power 2.4 GHz PA (for power 0 dBm and lower)

• EFR32xG22
  • A high-power 2.4 GHz PA (for power 6 dBm and lower)**
  • A low-power 2.4 GHz PA (for power 0 dBm and lower)

Each of these PAs has a unique number of discrete “power levels”, which are simply abstractions of the different register settings that control the active PA. For each PA, the following power levels are available:

• EFR32xG1x
  • High-power 2.4 Ghz: 0-252**
  • Low-power 2.4 Ghz: 1-7
  • Sub-GHz: 0-248

• EFR32xG21
  • High-power 2.4 Ghz: 1-180**
  • Medium-power 2.4 Ghz: 1-90
  • Low-power 2.4 Ghz: 1-64

• EFR32xG22
  • High-power 2.4 Ghz: 0-128**
  • Low-power 2.4 Ghz: 0-15

*Note that the use of 'high', 'medium', and 'low' in the names of these PAs refers to power consumption, not power output. It is possible, for instance, to configure the high-power PA to transmit at a lower dBm output than the low-power PA.

**Maximum power/use of these PAs may be restricted by your specific OPN. Please see the data sheet for more details regarding your particular part.

For more details and to set custom power curves for your design, refer AN1127: Power Amplifier Power Conversion Functions in RAIL 2.x