NRF52811-QCAA-R7 datasheet(196/444 Pages) NORDIC

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Peripherals

To choose the correct channel center frequency, the FREQUENCY register must be programmed according

to the table below.

IEEE 802.15.4 channel

Center frequency (MHz)

FREQUENCY setting

Channel 11

2405

Channel 12

2410

Channel 13

2415

Channel 14

2420

Channel 15

2425

Channel 16

2430

Channel 17

2435

Channel 18

2440

Channel 19

2445

Channel 20

2450

Channel 21

2455

Channel 22

2460

Channel 23

2465

Channel 24

2470

Channel 25

2475

Channel 26

2480

Table 67: IEEE 802.15.4 center frequency definition

6.14.13.3 Energy detection (ED)

As required by the IEEE 802.15.4 standard, it must be possible to sample the received signal power within

the bandwidth of a channel, for the purpose of determining presence of activity.

To prevent the channel signal from being decoded, the shortcut between the READY event and the

START task should be disabled before putting the RADIO in receive mode. The energy detection (ED)

measurement time, where RSSI samples are averaged, is 8 symbol periods, corresponding to 128 µs. The

standard further specifies the measurement to be a number between 0 and 255, where 0 shall indicate

received power less than 10 dB above the selected receiver sensitivity. The power range of the ED values

must be at least a 40 dB linear mapping with accuracy of ±6 dB. See section 6.9.7 Receiver ED in the IEEE

802.15.4 standard for further details.

The following example shows how to perform a single energy detection measurement and convert to IEEE

802.15.4 scale.

IEEE 802.15.4 ED measurement example

#define ED_RSSISCALE 4 // From electrical specifications

uint8_t sample_ed(void)

{

int val;

NRF_RADIO->TASKS_EDSTART = 1; // Start

while (NRF_RADIO->EVENTS_EDEND != 1) {

// CPU can sleep here or do something else

// Use of interrupts are encouraged

}

val = NRF_RADIO->EDSAMPLE; // Read level

return (uint8_t)(val>63 ? 255 : val*ED_RSSISCALE); // Convert to IEEE

802.15.4 scale

}

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