ATMEL nRF24L01 Datasheet

All rights reserved.

Reproduction in whole or in part is prohibited without the prior written permission of the copyright holder.

July 2007

nRF24L01
Single Chip 2.4GHz Transceiver

Product Specification

Key Features

• Worldwide 2.4GHz ISM band operation

• Up to 2Mbps on air data rate

• Ultra low power operation

• 11.3mA TX at 0dBm output power

• 12.3mA RX at 2Mbps air data rate

• 900nA in power down

• 22µA in standby-I

• On chip voltage regulator

• 1.9 to 3.6V supply range

• Enhanced ShockBurst™

• Automatic packet handling

• Auto packet transaction handling

• 6 data pipe MultiCeiver™

• Air compatible with nRF2401A, 02, E1 and
E2

• Low cost BOM

• ±60ppm 16MHz crystal

• 5V tolerant inputs

• Compact 20-pin 4x4mm QFN package

Applications

• Wireless PC Peripherals

• Mouse, keyboards and remotes

• 3-in-one desktop bundles

• Advanced Media center remote controls

• VoIP headsets

• Game controllers

• Sports watches and sensors

• RF remote controls for consumer electronics

• Home and commercial automation

• Ultra low power sensor networks

•Active RFID

• Asset tracing systems

•Toys

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nRF24L01 Product Specification

Liability disclaimer

Nordic Semiconductor ASA reserves the right to make changes without further notice to the product to
improve reliability, function or design. Nordic Semiconductor ASA does not assume any liability arising out
of the application or use of any product or circuits described herein.

All application information is advisory and does not form part of the specification.

Limiting values

Stress above one or more of the limiting values may cause permanent damage to the device. These are
stress ratings only and operation of the device at these or at any other conditions above those given in the
specifications are not implied. Exposure to limiting values for extended periods may affect device reliability.

Life support applications

These products are not designed for use in life support appliances, devices, or systems where malfunction
of these products can reasonably be expected to result in personal injury. Nordic Semiconductor ASA cus­tomers using or selling these products for use in such applications do so at their own risk and agree to fully
indemnify Nordic Semiconductor ASA for any damages resulting from such improper use or sale.

Contact details

Visit www.nordicsemi.no for Nordic Semiconductor sales offices and distributors worldwide

Main office:

Otto Nielsens vei 12

7004 Trondheim

Phone: [phone]

Fax: [phone]

www.nordicsemi.no

Data sheet status

Objective product specification This product specification contains target specifications for product

development.

Preliminary product specification This product specification contains preliminary data; supplementary

data may be published from Nordic Semiconductor ASA later.

Product specification This product specification contains final product specifications. Nordic

Semiconductor ASA reserves the right to make changes at any time
without notice in order to improve design and supply the best possible
product.

Revision 2.0 Page 3 of 74

nRF24L01 Product Specification

Writing Conventions

This product specification follows a set of typographic rules that makes the document consistent and easy
to read. The following writing conventions are used:

• Commands, bit state conditions, and register names are written in Courier.

• Pin names and pin signal conditions are written in Courier bold.

• Cross references are underlined and highlighted in blue

.

Revision History

Date Version Description

July 2007 2.0

• Restructured layout in a new template

• Added details of the following features:

X Dynamic Payload Length (DPL)
X Acknowledgement Payload (ACK_PLD)
X Feature register
X ACTIVATE SPI command
X Selective Auto Acknowledgement (NO_ACK)

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nRF24L01 Product Specification

Contents

1 Introduction ............................................................................................... 7

1.1 Features ............................................................................................... 8

1.2 Block diagram ...................................................................................... 9

2 Pin Information.......................................................................................... 10

2.1 Pin assignment..................................................................................... 10

2.2 Pin functions......................................................................................... 11

3 Absolute maximum ratings ...................................................................... 12

4 Operating conditions ................................................................................ 13

5 Electrical specifications ........................................................................... 14

5.1 Power consumption.............................................................................. 14

5.2 General RF conditions ......................................................................... 15

5.3 Transmitter operation ........................................................................... 15

5.4 Receiver operation ............................................................................... 16

5.5 Crystal specifications ........................................................................... 17

5.6 DC characteristics ................................................................................ 18

5.7 Power on reset ..................................................................................... 18

6 Radio Control ............................................................................................ 19

6.1 Operational Modes............................................................................... 19

6.1.1 State diagram .................................................................................. 19

6.1.2 Power Down Mode .......................................................................... 20

6.1.3 Standby Modes................................................................................ 20

6.1.4 RX mode.......................................................................................... 21

6.1.5 TX mode .......................................................................................... 21

6.1.6 Operational modes configuration..................................................... 21

6.1.7 Timing Information........................................................................... 22

6.2 Air data rate.......................................................................................... 22

6.3 RF channel frequency .......................................................................... 23

6.4 PA control............................................................................................. 23

6.5 LNA gain .............................................................................................. 23

6.6 RX/TX control....................................................................................... 23

7 Enhanced ShockBurst™ .......................................................................... 24

7.1 Features ............................................................................................... 24

7.2 Enhanced ShockBurst™ overview....................................................... 24

7.3 Enhanced Shockburst™ packet format................................................ 25

7.3.1 Preamble ......................................................................................... 25

7.3.2 Address ........................................................................................... 25

7.3.3 Packet Control Field ........................................................................ 25

7.3.4 Payload............................................................................................ 26

7.3.5 CRC (Cyclic Redundancy Check) ................................................... 26

7.4 Automatic packet handling ................................................................... 26

7.4.1 Static and Dynamic Payload Length................................................ 26

7.4.2 Automatic packet assembly............................................................. 27

7.4.3 Automatic packet validation............................................................. 27

7.4.4 Automatic packet disassembly ........................................................ 28

7.5 Automatic packet transaction handling ................................................ 28

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nRF24L01 Product Specification

7.5.1 Auto Acknowledgement................................................................... 29

7.5.2 Auto Retransmission (ART)............................................................. 29

7.6 Enhanced ShockBurst flowcharts ........................................................ 31

7.6.1 PTX operation.................................................................................. 31

7.6.2 PRX operation ................................................................................. 33

7.7 Multiceiver ............................................................................................ 35

7.8 Enhanced ShockBurstTM timing.......................................................... 38

7.9 Enhanced ShockBurstTM transaction diagram.................................... 40

7.9.1 Single transaction with ACK packet and interrupts.......................... 40

7.9.2 Single transaction with a lost packet ............................................... 41

7.9.3 Single transaction with a lost ACK packet ....................................... 41

7.9.4 Single transaction with ACK payload packet ................................... 42

7.9.5 Single transaction with ACK payload packet and lost packet.......... 42

7.9.6 Two transactions with ACK payload packet and the first

ACK packet lost ............................................................................... 43

7.9.7 Two transactions where max retransmissions is reached ............... 43

7.10 Compatibility with ShockBurst™ .......................................................... 44

7.10.1 ShockBurst™ packet format............................................................ 44

8 Data and Control Interface ....................................................................... 45

8.1 Features ............................................................................................... 45

8.2 Functional description .......................................................................... 45

8.3 SPI operation ....................................................................................... 45

8.3.1 SPI Commands ............................................................................... 45

8.3.2 SPI timing ........................................................................................ 47

8.4 Data FIFO ............................................................................................ 51

8.5 Interrupt................................................................................................ 52

9 Register Map.............................................................................................. 53

9.1 Register map table ............................................................................... 53

10 Peripheral RF Information ........................................................................ 59

10.1 Antenna output..................................................................................... 59

10.2 Crystal oscillator................................................................................... 59

10.3 nRF24L01 sharing crystal with an MCU............................................... 59

10.3.1 Crystal parameters .......................................................................... 59

10.3.2 Input crystal amplitude and current consumption ............................ 59

10.4 PCB layout and decoupling guidelines................................................. 60

11 Mechanical specifications........................................................................ 61

12 Ordering information ................................................................................ 63

12.1 Package marking ................................................................................. 63

12.2 Abbreviations ....................................................................................... 63

13 Glossary of Terms..................................................................................... 64

Appendix A - Enhanced ShockBurst™ - Configuration

and Communication Example.................................................................. 65

Enhanced ShockBurst™ Transmitting Payload ................................... 65

Enhanced ShockBurst™ Receive Payload .......................................... 65

Appendix B - Configuration for compatibility with nRF24XX................ 67

Appendix C - Carrier wave output power................................................ 68

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nRF24L01 Product Specification

Configuration........................................................................................ 68

Appendix D - Application example .......................................................... 69

PCB layout examples........................................................................... 70

Appendix E - Stationary disturbance detection ..................................... 74

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nRF24L01 Product Specification

1 Introduction

The nRF24L01 is a single chip 2.4GHz transceiver with an embedded baseband protocol engine
(Enhanced ShockBurst™), designed for ultra low power wireless applications. The nRF24L01 is designed
for operation in the world wide ISM frequency band at 2.400 - 2.4835GHz. An MCU (microcontroller) and
very few external passive components are needed to design a radio system with the nRF24L01.

The nRF24L01 is configured and operated through a Serial Peripheral Interface (SPI.) Through this inter­face the register map is available. The register map contains all configuration registers in the nRF24L01
and is accessible in all operation modes of the chip.

The embedded baseband protocol engine (Enhanced ShockBurst™) is based on packet communication
and supports various modes from manual operation to advanced autonomous protocol operation. Internal
FIFOs ensure a smooth data flow between the radio front end and the system’s MCU. Enhanced Shock­Burst™ reduces system cost by handling all the high-speed link layer operations.

The radio front end uses GFSK modulation. It has user configurable parameters like frequency channel,
output power and air data rate.

The air data rate supported by the nRF24L01 is configurable to 2Mbps. The high air data rate combined
with two power saving modes makes the nRF24L01 very suitable for ultra low power designs.

Internal voltage regulators ensure a high Power Supply Rejection Ratio (PSRR) and a wide power supply
range.

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nRF24L01 Product Specification

1.1 Features

Features of the nRF24L01 include:

•Radio

X Worldwide 2.4GHz ISM band operation
X 126 RF channels
X Common RX and TX pins
X GFSK modulation
X 1 and 2Mbps air data rate
X 1MHz non-overlapping channel spacing at 1Mbps
X 2MHz non-overlapping channel spacing at 2Mbps

• Transmitter

X Programmable output power: 0, -6, -12 or -18dBm
X 11.3mA at 0dBm output power

• Receiver

X Integrated channel filters
X 12.3mA at 2Mbps
X -82dBm sensitivity at 2Mbps
X -85dBm sensitivity at 1Mbps
X Programmable LNA gain

• RF Synthesizer

X Fully integrated synthesizer
X No external loop filer, VCO varactor diode or resonator
X Accepts low cost ±60ppm 16MHz crystal

• Enhanced ShockBurst™

X 1 to 32 bytes dynamic payload length
X Automatic packet handling
X Auto packet transaction handling
X 6 data pipe MultiCeiver™ for 1:6 star networks

• Power Management

X Integrated voltage regulator
X 1.9 to 3.6V supply range
X Idle modes with fast start-up times for advanced power management
X 22uA Standby-I mode, 900nA power down mode
X Max 1.5ms start-up from power down mode
X Max 130us start-up from standby-I mode

• Host Interface

X 4-pin hardware SPI
X Max 8Mbps
X 3 separate 32 bytes TX and RX FIFOs
X 5V tolerant inputs

• Compact 20-pin 4x4mm QFN package

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nRF24L01 Product Specification

1.2 Block diagram

Figure 1. nRF24L01 block diagram

RF Receiver

XC1

XC2

ANT1

ANT2

Enhanced ShockBurst

Baseband Engine

TX FIFOs

RX FIFOs

Radio Control

GFSK

Modulator

SPI

PA

LNA

TX

Filter

RX

Filter

RF Synthesiser Power Management

RF Transmitter Baseband

CSN

SCK

MISO

MOSI

IRQ

CE

VSS

VDD

DVDD

VDD_PA

GFSK

Demodulator

Register map

IREF

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nRF24L01 Product Specification

2 Pin Information

2.1 Pin assignment

Figure 2. nRF24L01 pin assignment (top view) for the QFN20 4x4 package

CE

CSN

SCK

MOSI

MISO

VDD

VSS

ANT2

ANT1

VDD_PA

IRQ

VDD

VSS

XC2

XC1

VSS

DVDD

VDD

VSS

IREF

1

2

3

4

5

15

14

13

12

11

6 7 8 9 10

1617181920

nRF24L01

QFN20 4X4

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nRF24L01 Product Specification

2.2 Pin functions

Table 1. nRF24L01 pin function

Pin Name Pin function Description

1 CE Digital Input Chip Enable Activates RX or TX mode
2 CSN Digital Input SPI Chip Select
3 SCK Digital Input SPI Clock
4 MOSI Digital Input SPI Slave Data Input
5 MISO Digital Output SPI Slave Data Output, with tri-state option
6 IRQ Digital Output Maskable interrupt pin. Active low
7 VDD Power Power Supply (+1.9V - +3.6V DC)
8 VSS Power Ground (0V)

9 XC2 Analog Output Crystal Pin 2
10 XC1 Analog Input Crystal Pin 1
11 VDD_PA Power Output Power Supply Output(+1.8V) for the internal

nRF24L01 Power Amplifier. Must be con­nected to ANT1 and ANT2 as shown in Fig-

ure 30.

12 ANT1 RF Antenna interface 1
13 ANT2 RF Antenna interface 2
14 VSS Power Ground (0V)
15 VDD Power Power Supply (+1.9V - +3.6V DC)
16 IREF Analog Input Reference current. Connect a 22kΩ resistor

to ground. See: Figure 30.
17 VSS Power Ground (0V)
18 VDD Power Power Supply (+1.9V - +3.6V DC)
19 DVDD Power Output Internal digital supply output for de-coupling

purposes. See: Figure 30.
20 VSS Power Ground (0V)

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nRF24L01 Product Specification

3 Absolute maximum ratings

Note: Exceeding one or more of the limiting values may cause permanent damage to nRF24L01.

Table 2. Absolute maximum ratings

Operating conditions Minimum Maximum Units

Supply voltages

VDD -0.3 3.6 V
VSS 0V

Input voltage

V

I

-0.3 5.25 V

Output voltage

V

O

VSS to VDD VSS to VDD

Total Power Dissipation

P

D (TA

=85°C) 60 mW

Temperatures

Operating Temperature -40 +85 °C
Storage Temperature -40 +125 °C

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nRF24L01 Product Specification

4 Operating conditions

Table 3. Operating conditions

Symbol Parameter (condition) Notes Min. Typ . Max. Units

VDD Supply voltage 1.9 3.0 3.6 V
VDD

Supply voltage if input signals >3.6V

2.7 3.0 3.3 V

TEMP Operating Temperature -40 +27 +85 ºC

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nRF24L01 Product Specification

5 Electrical specifications

Conditions: VDD = +3V, VSS = 0V, TA = - 40ºC to + 85ºC

5.1 Power consumption

Table 4.Power consumption

Symbol Parameter (condition) Notes Min. Typ. Max. Units

Idle modes

I

VDD_PD

Supply current in power down 900 nA

I

VDD_ST1

Supply current in standby-I mode

a

a. Current is given for a 12pF crystal. Current when using external clock is dependent on signal swing.

22 μA

I

VDD_ST2

Supply current in standby-II mode 320 μA

I

VDD_SU

Average current during 1.5ms crystal
oscillator startup

285 μA

Transmit

I

VDD_TX0

Supply current @ 0dBm output power

b

b. Antenna load impedance = 15Ω+j88Ω.

11.3 mA

I

VDD_TX6

Supply current @ -6dBm output
power

b

9.0 mA

I

VDD_TX12

Supply current @ -12dBm output
power

b

7.5 mA

I

VDD_TX18

Supply current @ -18dBm output
power

b

7.0 mA

I

VDD_AVG

Average Supply current @ -6dBm out­put power, Enhanced ShockBurst™

c

c. Antenna load impedance = 15Ω+j88Ω. Average data rate 10kbps and full packets

0.12 mA

I

VDD_TXS

Average current during TX settling

d

d. Average current consumption for TX startup (130µs) and when changing mode from RX to TX (130µs).

8.0 mA

Receive

I

VDD_2M

Supply current 2Mbps 12.3 mA

I

VDD_LC

Supply current 2Mbps
LNA low current

11.5 mA

I

VDD_1M

Supply current 1Mbps 11.8 mA

I

VDD_LC

Supply current 1Mbps
LNA low current

11.1 mA

I

VDD_RXS

Average current during RX settling

e

e. Average current consumption for RX startup (130µs) and when changing mode from TX to RX (130µs).

8.4 mA

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nRF24L01 Product Specification

5.2 General RF conditions

Table 5. General RF conditions

5.3 Transmitter operation

Table 6.Transmitter operation

Symbol Parameter (condition) Notes Min. Typ. Max. Units

f

OP

Operating frequency

a

a. Usable band is determined by local regulations

2400 2525 MHz

PLL

res

PLL Programming resolution 1 MHz

f

XTAL

Crystal frequency 16 MHz

Δf

1M

Frequency deviation @ 1Mbps ±160 kHz

Δf

2M

Frequency deviation @ 2Mbps ±320 kHz

R

GFSK

Air Data rate

b

b. Data rate in each burst on-air

1000 2000 kbps

F

CHAN-

NEL 1M

Non-overlapping channel spac­ing @ 1Mbps

c

c. The minimum channel spacing is 1Mhz

1MHz

F

CHAN-

NEL 2M

Non-overlapping channel spac­ing @ 2Mbps

c

2MHz

Symbol Parameter (condition) Notes Min. Typ . Max. Units

P

RF

Maximum Output Power

a

a. Antenna load impedance = 15Ω+j88Ω

0+4dBm

P

RFC

RF Power Control Range 16 18 20 dB

P

RFCR

RF Power Accuracy ±4 dB

P

BW2

20dB Bandwidth for Modulated Carrier
(2Mbps)

1800 2000 kHz

P

BW1

20dB Bandwidth for Modulated Carrier
(1Mbps)

900 1000 kHz

P

RF1

1st Adjacent Channel Transmit Power
2MHz

-20 dBm

P

RF2

2nd Adjacent Channel Transmit Power
4MHz

-50 dBm

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nRF24L01 Product Specification

5.4 Receiver operation

Table 7. Receiver operation

Symbol Parameter (condition) Notes Min. Typ . Max. Units

RX

max

Maximum received signal at <0.1% BER 0 dBm

RX

SENS

Sensitivity (0.1%BER) @2Mbps -82 dBm

RX

SENS

Sensitivity at (0.1%BER) @1Mbps -85 dBm

RX selectivity according to ETSI EN 300 440-1 V1.3.1 (2001-09) page 27

C/I

CO

C/I Co-channel (@2Mbps)

a

a. Data rate is 2Mbps for the following C/I measurements

7dB

C/I

1ST

1st Adjacent Channel Selectivity C/I 2MHz

1dB

C/I

2ND

2nd Adjacent Channel Selectivity C/I 4MHz

-21 dB

C/I

3RD

3rd Adjacent Channel Selectivity C/I 6MHz

-27 dB

C/I

CO

C/I Co-channel (@1Mbps)

b

b. Data rate is 1Mbps for the following C/I measurements

9dB

C/I

1ST

1st Adjacent Channel Selectivity C/I 1MHz

8dB

C/I

2ND

2nd Adjacent Channel Selectivity C/I 2MHz

-22 dB

C/I

3RD

3rd Adjacent Channel Selectivity C/I 3MHz

-30 dB

RX selectivity with nRF24L01 equal modulation on interfering signal

C/I

CO

C/I Co-channel (@2Mbps) (Modulated car­rier)

a

11 dB

C/I

1ST

1st Adjacent Channel Selectivity C/I 2MHz

4dB

C/I

2ND

2nd Adjacent Channel Selectivity C/I 4MHz

-20 dB

C/I

3RD

3rd Adjacent Channel Selectivity C/I 6MHz

-27 dB

C/I

CO

C/I Co-channel (@1Mbps)

b

12 dB

C/I

1ST

1st Adjacent Channel Selectivity C/I 1MHz

8dB

C/I

2ND

2nd Adjacent Channel Selectivity C/I 2MHz

-21 dB

C/I

3RD

3rd Adjacent Channel Selectivity C/I 3MHz

-30 dB

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nRF24L01 Product Specification

5.5 Crystal specifications

Table 8. Crystal specifications

Symbol Parameter (condition) Notes Min. Typ. Max. Units

Fxo Crystal Frequency 16 MHz

ΔF Tolerance

a b

a. Frequency accuracy including; tolerance at 25ºC, temperature drift, aging and crystal loading.
b. Frequency regulations in certain regions sets tighter requirements to frequency tolerance (Ex:

Japan and Korea max. +/- 50ppm)

±60 ppm

C

0

Equivalent parallel capacitance 1.5 7.0 pF

C

L

Load capacitance 8 12 16 pF

ESR Equivalent Series Resistance 100 Ω

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nRF24L01 Product Specification

5.6 DC characteristics

Table 9. Digital input pin

Table 10. Digital output pin

5.7 Power on reset

Table 11. Power on reset

Symbol Parameter (condition) Notes Min. Typ . Max. Units

V

IH

HIGH level input voltage 0.7VDD

5.25

a

a. If the input signal >3.6V, the VDD of the nRF24L01 must be between 2.7V and 3.3V (3.0V±10%)

V

V

IL

LOW level input voltage VSS 0.3VDD V

Symbol Parameter (condition) Notes Min. Typ . Max. Units

V

OH

HIGH level output voltage (IOH=-0.25mA) VDD -0.3 VDD V

V

OL

LOW level output voltage (IOL=0.25mA) 0.3 V

Symbol Parameter (condition) Notes Min. Typ . Max. Units

T

PUP

Power ramp up time

a

a. From 0V to 1.9V

100 ms

T

POR

Power on reset

b

b. Measured when the VDD reaches 1.9V to when the reset finishes

1.6 5.3 10.3 ms

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nRF24L01 Product Specification

6 Radio Control

This chapter describes the different modes the nRF24L01 radio transceiver can operate in and the param­eters used to control the radio.

The nRF24L01 has a built-in state machine that controls the transitions between the different operating
modes of the chip. The state machine takes input from user defined register values and internal signals.

6.1 Operational Modes

The nRF24L01 can be configured in four main modes of operation. This section describes these modes.

6.1.1 State diagram

The state diagram (Figure 3.) shows the modes the nRF24L01 can operate in and how they are accessed.
The nRF24L01 is undefined until the VDD becomes 1.9V or higher. When this happens nRF24L01 enters
the Power on reset state where it remains in reset until it enters the Power Down mode. Even when the
nRF24L01 enters Power Down mode the MCU can control the chip through the SPI and the Chip Enable
(CE) pin Three types of states are used in the state diagram. “Recommended operating mode” is a state
that is used during normal operation. “Possible operating mode” is a state that is allowed to use, but it is
not used during normal operation. “Transition state” is a time limited state used during start up of the oscil­lator and settling of the PLL.

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nRF24L01 Product Specification

.

Figure 3. Radio control state diagram

6.1.2 Power Down Mode

In power down mode nRF24L01 is disabled with minimal current consumption. In power down mode all the
register values available from the SPI are maintained and the SPI can be activated. For start up time see

Table 13. on page 22

. Power down mode is entered by setting the PWR_UP bit in the CONFIG register low.

6.1.3 Standby Modes

By settting the PWR_UP bit in the CONFIG register to 1, the device enters standby-I mode. Standby-I mode
is used to minimize average current consumption while maintaining short start up times. In this mode part
of the crystal oscillator is active. This is the mode the nRF24L01 returns to from TX or RX mode when CE
is set low.

In standby-II mode extra clock buffers are active compared to standby-I mode and much more current is
used compared to standby-I mode. Standby-II occurs when CE is held high on a PTX device with empty TX
FIFO. If a new packet is uploaded to the TX FIFO, the PLL starts and the packet is transmitted.

VDD >= 1.9V

Undefined

Power on

reset

10.3ms

Power Down

Standby-I

RX Mode

TX Mode

Standby-II

RX Settling

130 us

Start up

1.5ms

PWR_UP = 1

PWR_UP = 0

TX Settling

130 us

TX FIFO not empty
PRIM_RX = 0
CE = 1 for more than 10µs

PRIM_RX = 1
CE = 1

CE = 0

TX FIFO empty
CE = 1

TX FIFO not empty
CE = 1

PRIM_RX = 0
TX FIFO empty
CE = 1

PWR_UP = 0

PWR_UP = 0

PWR_UP=0

CE = 0

PWR_UP=0

PWR_UP=0

TX finished with one packet
CE = 0

CE = 1
TX FIFO not empty

Possible operating mode

Recommended path between operating modes

Possible path between operating modes

Recommended operating mode

Transition state

CE = 1

Pin signal condition

PWR_DN = 1

Bit state condition

Undefined

TX FIFO empty

System information

Undefined

Legend:

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nRF24L01 Product Specification

The register values are maintained during standby modes and the SPI may be activated. For start up time
see Table 13. on page 22

.

6.1.4 RX mode

The RX mode is an active mode where the nRF24L01 radio is a receiver. To enter this mode, the
nRF24L01 must have the PWR_UP bit set high, PRIM_RX bit set high and the CE pin set high.

In this mode the receiver demodulates the signals from the RF channel, constantly presenting the demod­ulated data to the baseband protocol engine. The baseband protocol engine constantly searches for a
valid packet. If a valid packet is found (by a matching address and a valid CRC) the payload of the packet
is presented in a vacant slot in the RX FIFO. If the RX FIFO is full, the received packet is discarded.

The nRF24L01 remains in RX mode until the MCU configures it to standby-I mode or power down mode. If
the automatic protocol features (Enhanced ShockBurst™) in the baseband protocol engine are enabled,
the nRF24L01 can enter other modes in order to execute the protocol.

In RX mode a carrier detect signal is avaliable. The carrier detect is a signal that is set high when a RF sig­nal is detected inside the receiving frequency channel. The signal must be FSK modulated for a secure
detection. Other signals can also be detected. The Carrier Detect (CD) is set high when an RF signal is
detected in RX mode, otherwise CD is low. The internal CD signal is filtered before presented to CD register.
The RF signal must be present for at least 128µs before the CD is set high. How to use the CD is described
in Appendix E on page 74

.

6.1.5 TX mode

The TX mode is an active mode where the nRF24L01 transmits a packet. To enter this mode, the
nRF24L01 must have the PWR_UP bit set high, PRIM_RX bit set low, a payload in the TX FIFO and, a high
pulse on the CE for more than 10µs.

The nRF24L01 stays in TX mode until it finishes transmitting a current packet. If CE = 0 nRF24L01 returns
to standby-I mode. If CE = 1, the next action is determined by the status of the TX FIFO. If the TX FIFO is
not empty the nRF24L01 remains in TX mode, transmitting the next packet. If the TX FIFO is empty the
nRF24L01 goes into standby-II mode.The nRF24L01 transmitter PLL operates in open loop when in TX
mode. It is important to never keep the nRF24L01 in TX mode for more than 4ms at a time. If the auto
retransmit is enabled, the nRF24L01 is never in TX mode long enough to disobey this rule.

6.1.6 Operational modes configuration

The following table (Table 12.) describes how to configure the operational modes.

Mode

PWR_UP

register

PRIM_RX

register

CE FIFO state

RX mode111­TX mode 1 0 1 Data in TX FIFO. Will empty all lev-

els in TX FIFO

a

.

TX mode 1 0 minimum 10μs

high pulse

Data in TX FIFO.Will empty one

level in TX FIFO

b

.
Standby-II 1 0 1 TX FIFO empty
Standby-I 1 - 0 No ongoing packet transmission
Power Down 0 - - -

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nRF24L01 Product Specification

Table 12. nRF24L01 main modes

6.1.7 Timing Information

The timing information in this section is related to the transitions between modes and the timing for the CE
pin. The transition from TX mode to RX mode or vice versa is the same as the transition from standby-I to
TX mode or RX mode,Tstby2a.

Table 13. Operational timing of nRF24L01

When nRF24L01 is in power down mode it must settle for 1.5ms before it can enter the TX or RX modes. If
an external clock is used this delay is reduced to 150µs, see Table 13. on page 22

. The settling time must

be controlled by the MCU.

Note: The register value is lost if VDD is turned off. In this case, nRF24L01 must be configured

before entering the TX or RX modes.

6.2 Air data rate

The air data rate is the modulated signaling rate the nRF24L01 uses when transmitting and receiving data.

The air data rate can be 1Mbps or 2Mbps. The 1Mbps data rate gives 3dB better receiver sensitivity com­pared to 2Mbps. High air data rate means lower average current consumption and reduced probability of
on-air collisions.

The air data rate is set by the RF_DR bit in the RF_SETUP register.

A transmitter and a receiver must be programmed with the same air data rate to be able to communicate
with each other.

For compatibility with nRF2401A, nRF24E1, nRF2402 and nRF24E2 the air data rate must be set to
1Mbps.

a. In this operating mode if the CE is held high the TX FIFO is emptied and all necessary ACK and pos-

sible retransmits are carried out. The transmission continues as long as the TX FIFO is refilled. If the
TX FIFO is empty when the CE is still high, nRF24L01 enters standby-II mode. In this mode the trans­mission of a packet is started as soon as the

CSN is set high after a upload (UL) of a packet to TX

FIFO.

b. This operating mode pulses the

CE high for at least 10µs. This allows one packet to be transmitted.

This is the normal operating mode. After the packet is transmittet, the nRF24L01 enters standby-I
mode.

Name nRF24L01 Max. Min. Comments

Tpd2stby Power Down Î Standby mode 1.5ms Internal crystal

oscillator

Tpd2stby Power Down Î Standby mode 150µs With external

clock

Tstby2a Standby modes Î TX/RX mode 130µs

Thce Minimum CE high 10µs

Tpece2csn Delay from CE pos. edge to CSN low 4µs

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nRF24L01 Product Specification

6.3 RF channel frequency

The RF channel frequency determines the center of the channel used by the nRF24L01. The channel
occupies a bandwidth of 1MHz at 1Mbps and 2MHz at 2Mbps. nRF24L01 can operate on frequencies from

2.400GHz to 2.525GHz. The resolution of the RF channel frequency setting is 1MHz.

At 2Mbps the channel occupies a bandwidth wider than the resolution of the RF channel frequency setting.
To ensure non-overlapping channels in 2Mbps mode, the channel spacing must be 2MHz or more. At
1Mbps the channel bandwidth is the same as the resolution of the RF frequency setting.

The RF channel frequency is set by the RF_CH register according to the following formula:

F

0

= 2400 + RF_CH [MHz]

A transmitter and a receiver must be programmed with the same RF channel frequency to be able to com­municate with each other.

6.4 PA control

The PA control is used to set the output power from the nRF24L01 power amplifier (PA). In TX mode PA
control has four programmable steps, see Table 14.

The PA control is set by the RF_PWR bits in the RF_SETUP register.

Conditions: VDD = 3.0V, VSS = 0V, T

A

= 27ºC, Load impedance = 15Ω+j88Ω.

Table 14. RF output power setting for the nRF24L01

6.5 LNA gain

The gain in the Low Noise Amplifier (LNA) in the nRF24L01 receiver is controlled by the LNA gain setting.
The LNA gain makes it possible to reduce the current consumption in RX mode with 0.8mA at the cost of

1.5dB reduction in receiver sensitivity.

The LNA gain has two steps and is set by the LNA_HCURR bit in the RF_SETUP register.

6.6 RX/TX control

The RX/TX control is set by PRIM_RX bit in the CONFIG register and sets the nRF24L01 in transmit/
receive.

SPI RF-SETUP

(RF_PWR)

RF output power

DC current

consumption

11 0d B m 11.3mA
10 -6dBm 9.0mA
01 -12dBm 7.5mA
00 -18dBm 7.0mA