NRF52811-QCAA-R7 datasheet(187/444 Pages) NORDIC

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Peripherals

RXRU

S0 L S1

PAYLOAD

CRC

RXDISABLE

S0 L S1

PAYLOAD

CRC

’X’

RXIDLE

Figure 68: Reception of multiple packets

6.14.8 Received signal strength indicator (RSSI)

The RADIO implements a mechanism for measuring the power in the received signal. This feature is called

received signal strength indicator (RSSI).

The RSSI is measured continuously and the value filtered using a single-pole IIR filter. After a signal level

change, the RSSI will settle after approximately RSSISETTLE.

Sampling of the received signal strength is started by using the RSSISTART task. The sample can be read

from the RSSISAMPLE register.

The sample period of the RSSI is defined by RSSIPERIOD. The RSSISAMPLE will hold the pre-filtered received

signal strength after this sample period.

For the RSSI sample to be valid, the RADIO has to be enabled in receive mode (RXEN task) and the

reception has to be started (READY event followed by START task).

6.14.9 Interframe spacing (IFS)

Interframe spacing (IFS) is defined as the time, in microseconds, between two consecutive packets,

starting from when the end of the last bit of the previous packet is received, to the beginning of the first

bit of the subsequent packet that is transmitted. The RADIO is able to enforce this interval, as specified in

the TIFS register, as long as the TIFS is not specified to be shorter than the RADIO's turnaround time, i.e.

the time needed to switch off the receiver, and then switch the transmitter back on. The TIFS register can

be written any time before the last bit on air is received.

This timing is illustrated in the figure below.

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