RSSI Measurement

This section describes, how the value for the received signal strength indication (RSSI) can be obtained for the current channel. The RSSI value is a generic radio receiver technology metric. It is updated internally in the radio transceiver every 2 us and can be read from the register RG_PHY_RSSI, which has a valid range from 0 ... 28. The actual RF input power is calculated by:

• PHY_RSSI = 0 : PRF/dBm < RSSI_BASE_VAL
• 0 < PHY_RSSI < 28 : PRF/dBm = RSSI_BASE_VAL + 3 * (PHY_RSSI - 1).
• PHY_RSSI = 28 : PRF/dBm >= RSSI_BASE_VAL + 81

There are the following two methods defined:

• PHY_GET_RSSI
• PHY_GET_FRAME_RSSI

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PHY_GET_RSSI

The RSSI value can be read from the sub register SR_RSSI whenever the radio transceiver is in one of the [RX_BASIC] states.

Note:

It is also possible to read the RSSI value in RX_AACK_ON but not in BUSY_RX_AACK. In this state it is not possible to determine if the radio transceiver is internally in receive mode or transmit mode (for sending the ACK frame).

Code example

    rssi = trx_bit_read(SR_RSSI);
    proc_rssi(rssi);

PHY_GET_FRAME_RSSI

The RSSI value for the currently received frame can be read from the sub register SR_RSSI right after the TRX_IRQ_RX_START interrupt and before the corresponding TRX_IRQ_TRX_END interrupt.

Code example

    /* TRX_IRQ_RX_START occurs here */
    rssi = trx_bit_read(SR_RSSI);
    proc_rssi(rssi);
    /* TRX_IRQ_TRX_END occurs here */

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