It looks like -40 dBm is the minimum...
/**
* @brief This command sets the TX power level of the device. By controlling the
PA_LEVEL, that determines the output power level (dBm) at the IC pin.
When the system starts up or reboots, the default TX power level will be used, which is the
maximum value of 6 dBm. Once this command is given, the output power will be changed
instantly, regardless if there is Bluetooth communication going on or not. For example, for
debugging purpose, the device can be set to advertise all the time. And use this
command to observe the signal strength changing.
The system will keep the last received TX power level from the command, i.e. the 2nd
command overwrites the previous TX power level. The new TX power level remains until
another Set TX Power command, or the system reboots.
* @param En_High_Power Enable High Power mode - Deprecated and ignored on STM32WB
* Values:
- 0x00: Standard Power
- 0x01: High Power
* @param PA_Level Power amplifier output level. Output power is indicative and it depends on the PCB layout and associated
components.Here the values are given at the IC pin
* Values:
- 0x00: -40 dBm
- 0x01: -20.85 dBm
- 0x02: -19.75 dBm
- 0x03: -18.85 dBm
- 0x04: -17.6 dBm
- 0x05: -16.5 dBm
- 0x06: -15.25 dBm
- 0x07: -14.1 dBm
- 0x08: -13.15 dBm
- 0x09: -12.05 dBm
- 0x0A: -10.9 dBm
- 0x0B: -9.9 dBm
- 0x0C: -8.85 dBm
- 0x0D: -7.8 dBm
- 0x0E: -6.9 dBm
- 0x0F: -5.9 dBm
- 0x10: -4.95 dBm
- 0x11: -4 dBm
- 0x12: -3.15 dBm
- 0x13: -2.45 dBm
- 0x14: -1.8 dBm
- 0x15: -1.3 dBm
- 0x16: -0.85 dBm
- 0x17: -0.5 dBm
- 0x18: -0.15 dBm
- 0x19: 0 dBm
- 0x1A: +1 dBm
- 0x1B: +2 dBm
- 0x1C: +3 dBm
- 0x1D: +4 dBm
- 0x1E: +5 dBm
- 0x1F: +6 dBm
* @retval Value indicating success or error code.
*/
tBleStatus aci_hal_set_tx_power_level(uint8_t En_High_Power,
uint8_t PA_Level);
