Front End Module (FEM) Utility#

Radio FEM Utility#

Enabling this optional software component includes default functionality related to FEM configuration. It also configures the GPIOs together with the Peripheral Reflex System (PRS) signals to control the FEM.

Configuration Options#

The following options can be configured:

• Enable RX Mode: Enables the output of RX based on the selected port and pin.

• Enable TX Mode: Enables the output of TX based on the selected port and pin.

• Enable Bypass Mode: Enables communication that bypasses the PA (Power Amplifier) and the LNA (Low Noise Amplifier) on the FEM.

• Enable TX High Power Mode: Enables high power transmit mode on the FEM, if disabled low power transmit will be used.

• Enable automatic PRS LNA Bypass Mode: Enables dynamic LNA bypass when receiving frames with high power.

  • SL_FEM_UTIL_AUTO_PRS_LNA_BYPASS_THRESHOLD: see RAIL_PrsLnaBypassConfig_t::threshold

  • SL_FEM_UTIL_AUTO_PRS_LNA_BYPASS_DELTA_RSSI_DMB: see RAIL_PrsLnaBypassConfig_t::deltaRssiDbm

  • SL_FEM_UTIL_AUTO_PRS_LNA_BYPASS_POLARITY: see RAIL_PrsLnaBypassConfig_t::polarity

  • SL_FEM_UTIL_AUTO_PRS_LNA_BYPASS_TIMEOUT_US: see RAIL_PrsLnaBypassConfig_t::timeoutUs

Typically, the signal routing is as follows:

• SL_FEM_UTIL_BYPASS: Bypass control (FEM pin CPS).

• SL_FEM_UTIL_RX: RX control (FEM pin CRX). Active based on the radio activity (whenever the LNA is enabled).

• SL_FEM_UTIL_SLEEP: Sleep control (FEM pin CSD). Active based on the radio activity (whenever the PA or LNA are enabled).

• SL_FEM_UTIL_TX: TX control (FEM pin CTX). Active based on the radio activity (whenever the PA is enabled).

• SL_FEM_UTIL_TX_HIGH_POWER: Tx power mode control (FEM pin CHL).

Refer to the FEM datasheet for the required settings as not all configuration options are applicable to every module.