I. counter, AES encryption accelerator, random generator

                             I.   Introduction

   The nRF24LE1 is a low-cost and high-performance
of 2.4 GHz RF transceivers system with embedded microcontrollers. The nRF24LE1
is optimized to provide a single chip solution for ULP wireless applications.
The combination of processing power, memory, low power oscillators, real-time
counter, AES encryption accelerator, random generator and a range of power
saving modes provides an ideal platform for implementation of RF protocols.
Benefits of using nRF24LE1 include tighter protocol timing, security, lower
power consumption and improved co-existence performance. For the application
layer the nRF24LE1 offers a rich set of peripherals including: SPI, 2-wire,
UART, 6 to 12 bit ADC, PWM and an ultra-low power analog comparator for voltage
level system wake-up. The nRF24LE1 comes in three different package variants:

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·        
An ultra-compact 4×4mm 24 pin QFN (7
generic I/O pins)

·        
A compact 5×5mm 32 pin QFN (15 generic I/O
pins)

·        
A 7×7mm 48 pin QFN (31 generic I/O pins)
The 4×4mm 24 pin QFN is ideal for low I/O count applications where small size
is key.

 

 II. FEATURES
AND WIRELESS TECHNOLOGY OF nRF24LE1

 
nRF24LE1 function: The nRF24LE1
microprocessor’s instruction system is compatible with industry standard 8051,
but the timing of the two is slightly different. Typically, the nRF24LE1
microcontroller, the instruction cycle is 4 to 20 instruction cycles, while the
industrial standard 8051 is the 12~48 clock cycle. The nRF24LE1 Interrupt
Controller supports ADC, SPI, RF receiver 1, RF receiver 2, wake-up timer, 5
interrupt sources. nRF24LE1 has 3 and 80,521 timers, in the traditional
asynchronous communication mode, the 8051 compliant UART can be used as the
baud rate generator of timer 1 and timer 2. The nRF24LE1 CPU integrates 2 data
pointers to facilitate data transfer with external RAM. The crystal oscillator
provides the clock source directly for the nRF24LE1 microcontroller. The
nRF24LE1 microcontroller has 256 bytes of data RAM and 512 bytes of ROM. After
a power-on reset or software initialization, the processor automatically loads
the code in the Rom boot area. User programs are typically loaded into 1 to 4KB
of RAM from an external serial EEPROM under boot, and this 4KB RAM can also be
used for storing data. If you do not use the mask ROM (that is, the included
ROM), the program code must be loaded from an external non-volatile memory. At
this point, the default boot zone uses the “generic 25320” EEPROM of
the SPI interface. In order to control the function of standard 8051, nRF24E1
added some special function registers, such as radio (P2), ADCCON, ADCDATAH, PWMCON,
PWMDUTY, RSTREAS, etc. It’s P0 and P1 are also different from standard 8051,
and most of the other SFRS are the same as standard 8051.

nRF24LE1
and ZigBee: The ZigBee is mainly applied between various
electronic devices with short distance range and low data transmission rate.
The ZigBee name comes from the communication way that the colony uses to
survive and develop, sealing information about the location, distance, and
direction of the newly discovered food source by jumping the dance of the
ZigBee shape. The ZigBee Alliance was founded in August 2001, in the second
half of 2002, the four giants of Invensys, Mitsubishi and Philips jointly
announced their alliance with ZigBee to develop the next generation of wireless
communications standards called ZigBee. So far, the alliance has about 27
member companies. All of these companies participated in the IEEE 802.15.4
Workgroup, which is responsible for developing the technical standards for the
ZigBee physical and media control layer. ZigBee Alliance is responsible for the
production of network layer above agreement. Currently, standard-setting work
has been completed. The ZigBee protocol is simpler to use than Bluetooth, a
high-speed personal area network or an 802.11x wireless LAN. ZigBee can be said
to be a brother of Bluetooth, it uses the 2.4GHz band, using frequency hopping
technology. Compared with Bluetooth, ZigBee is simpler, slower, less power and
less expensive. Its basic rate is 250kb/s, when reduced to 280kb/s, the
transmission range can be extended to 134 meters, and obtain higher
reliability. In addition, it can be networked with 254 nodes. Can be better
than Bluetooth support games, consumer electronics, instrumentation and home
automation applications. It is expected to expand ZigBee applications in the
fields of industrial monitoring, sensor networks, home monitoring, security
systems and toys.

nRF24LE1
and Bluetooth: Bluetooth technology was born in 1994,
Ericsson decided to develop a low-power, Low-cost wireless interface to build
mobile phone and its accessories communication. Can communicate or operate with
each other in close range. Its transmission band for the global public General
2.4GHz ISM band, providing 1Mbps transmission rate and 10 meters transmission
distance. The technology is also gaining support from industry giants in the PC
industry. 1998, Bluetooth Technology agreement by Ericsson, IBM, Intel, NOKIA,
Toshiba and other five companies to reach agreement. The standard version of
the Bluetooth protocol is 802.15.1, which is developed by the Bluetooth team
(SIG). 802.15.1’s initial standard is based on the 1.1 implementation, which is
built into the current many Bluetooth devices. New 802.15.1A is based on the
equivalent of Bluetooth 1.2 standard, with certain QoS characteristics, and
maintain latter compatibility. But the biggest obstacle of Bluetooth technology
is that the transmission range is limited, the general effective range is about
10 meters, the anti-interference ability is not strong, and the information
security problem is the main factor restricting its further development and
large-scale application. Therefore, industry experts believe that Bluetooth
market prospects depend on whether Bluetooth can effectively solve the above
constraints.

nRF24LE1
and Wi-Fi:  Wi-Fi is a
technology that allows PCs, handheld devices such as PDAs, mobile phones, and
other terminals to be connected wirelessly. Wi-Fi is a wireless internet
communication technology brand, held by Wi-Fi Alliance. The goal is to improve
interoperability between wireless network products based on IEEE 802.11
standards. At present, the average person will confuse Wi-Fi and IEEE 802.11.
Even the Wi-Fi equivalent to the wireless internet. Wi-Fi frequency is also
2.4GHz, with cordless phones, Bluetooth and many other wireless devices do not
need to use the license to share the same frequency band. With the new version
of the Wi-Fi protocol, such as 802.11A and 802.11g, Wi-Fi applications will be
more and more extensive. Faster 802.11g uses the same orthogonal frequency
division multiplexing modulation technology as 802.11B. It works in the 2.4GHz
band, the rate reaches 54mb/s,judging from the recent trends in International
consumer electronics, 802.11g is likely to be selected as a product standard by
most wireless network manufacturers. Wi-Fi helps users access Internet
technologies for e-mail, web, and streaming media. It provides wireless
broadband Internet access to users. It is also a quick and convenient way to
get online at home, in the office, or on the road. Places where you can access
Wi-Fi networks are called hotspots. Wi-Fi hotspots are created by installing
access points on an Internet connection. This access point transmits the
wireless signal over a short distance-typically covering 300 feet. Wi-Fi is a
wireless extension of Ethernet, theoretically, as long as the user is located
in a certain area around an access point, you can access the Web at a maximum
speed of about 54mb/s. But in fact, if there are multiple users at the same
time through a point of access, bandwidth is shared by multiple users, Wi-Fi
connection speed will generally only hundreds of KB of the signal is not
blocked by the wall, but the effective transmission distance within the
building is less than outdoor. The most promising applications for WLAN in the
future will be in SoHo, home wireless networks and buildings or places where
cables are inconvenient to install.

 

III. NRF24LE1 TRANSMITTER AND RECEIVER HARDWARE

A. Introduction

nRF24LU1
USB Converter Reference Design with nRF24LU1 embedded nRF24L01RF Transceiver
Compatible USB for Nordic Semiconductor Figure 1 shows the nRF24LU1 USB
Converter Reference Design.

             Figure
1: nRF24LU1 USB Converter

The
nRF24LU1 USB Converter has developed into a complete reference design, nRF24
LU1. This is a production ready design, light painted file and Altium Designer6
file that can be used in its current form or modified to develop its own
design. The reference design is certified USB and has been EMC tested. RF
authentication test reports and USB compliance reports are included in the CD. nRF24LU1
usually uses a USB interface for the mouse, keyboard, remote control, data
collection and transmission, communication and peripherals. The nRF24LU1 has
built-in MCU-compliant transceivers, which makes it ideal for MCU based
devices. In addition to transceivers, nRF24LU1 has a full speed USB2.0 standard
device controller, an 8-bit 8051MCU and 16KB flash memory. Voltage regulator
Integration in nRF24 LU1, nRF24LU1 can be provided directly from USB.

B. How
to use this reference design

  USB software dogs can be
used as a development platform. To start using the reference design, the first
step is usually to develop firmware. nRF24LU1 Software Development Kit,
software Development Kit, is a good starting point. This library and code
example can be used as a basic your own code. You can even use the Wireless
Desktop Protocol, the Women’s development program, it and just develop the
other end of the link. This reference design is ready to be used. The
photo-drawing file can be used for production-ready design. Therefore, you do
not need to change the design for a full USB converter. You may want to add a
housing design. When the shell is designed, it is important that the metal
fingers touch the transducer at the antenna end. Antennas may be affected by
the housing. It is important to check the performance with the internal printed
circuit board in the plastic casing and adjust the antenna if necessary. Most
plastics do not change antenna performance, but this must be tested in all
cases. Programming interfaces, J2, and programming if unwanted nRF24LU1 are
installed. Therefore, in mass production, the connector can be omitted. If you
want to change the design, Nordic countries Semiconductor provides altium
DESIGNER6 files, complete with library files and light painting files. These
files are included in the Suite CD.

 

C. nRF24LU1
USB Interface schematic diagram

nRF24LU1USB
Converter schematic diagram on the nRF24LU1 product specification. Figure 2
shows how the Nrf24lu1usb interface circuit works.

 

               
Figure 2 the working principle of nRF24LU1USB interface circuit

Electricity supply: nRF24LU1 connected
to the usb5v power supply through a 10 ohm resistor, nRF24LU1 has an internal
circuit with a built-in regulator. No additional power regulator is required in
this design for VDD pins only for internal coupling. They are connected
together and the decoupling capacitor is placed near the VDD pin suggested in
the product specification.

Matching Network: Match the network between the
components on the pins 0Ant nRF24LU1 and antennas. Its function is impedance
transformation and filtering. Make the USB converter as small as possible,
layout the matching network from the reference layout in the nRF24LU1 product
specification. Component values to compensate for changing the layout. If you
use a layout, in this document, the value of the component can be specified in
the BOM. It must be emphasized that if the layout of the home page changes, the
matching network and antennas must be tuned for optimal performance. The
components in this design are very sensitive and the layout has changed. If the
layout must be changed, the nRF24LU1 product specification from the matching
network layout.

Antenna: The antenna is one-fourth
wavelength along the winding circuit board type. The impedance of the antenna
matches the 50 ohm output matching the network using L4 and C13. When the
Nrf24lu1usb converter connects to the PC, the PC will add a significant ground
plane to the nRF24LU1USB cipher dog. This means that the measured value of any
antenna must be connected to the PC with the receiver. Of course not all PCs
are equal, so we will seek a compromise solution. The antenna is fixed in the
design where the layout is adjusted. If the layout changes, the antenna must be
adjusted. The reference design provides no housing. For an actual product, some
houses are encrypted with dogs. Some housing materials can have some impact on
the antenna. This can be done by changing the compensation value of the L4 and
the C13 so that the resonant frequency of the antenna is correct. The exact
component value must be measured.

Flash programming: The nRF24LU1 of flash memory uses
programmable nRF24LU1 USB converter programming adapters, SE figure 3. The
dimensions of the interface do not allow a full-size connector, and then put it
on the printed circuit board, so 5 pins, 1mm spacing connector is used instead.

Figure 3:  nRF24LU1 USB Dongle programming adapter

The ISP converter uses a level converter to program
logic-level devices. The ISP interface must have access to the same voltage
level device for programming. Because the connector, J2, has only 5 pins in the
nRF24LU1USB converter, there is no direct access to the VDD nRF24 LU1. A nRF24LU1USB
converter capable of regulating the VBUS power supply to a 3.0V programming
adapter and the same voltage converter on the ISP of the level converter. The
grounding connection is via a USB plug. To avoid increasing the grounding loops
due to noise, it is important to plug the Nrf24lu1usb interface directly into
the programming adapter instead of using a USB extension cable to connect the
programming adapter and the nRF2LU1USB converter. The nRF24LU1USB converter is
connected to the programming adapter as shown in Figure 4. The ISP dongle is
connected to the J2 programming adapter. Two ISP interface and USB interface on
the programming adapter, J2, need to have a computer USB connection.

Figure 4 –
nRF24LU1 USB Dongle Programming Adapter assembly

 

CONCLUSION

In this paper,
completed the use of nRF24LE1 wireless data transceiver implementation of the
design. Through the analysis of RF transceiver function, the principle of
wireless communication technology is designed, the function and characteristics
of nRF24LE1 are detailed, and the application of chip in the work of wireless
identification Data collector is designed. Throughout the process, the wireless
communication product development process has a deeper understanding. The
design of the wireless identification Data collector after the program is
fired, after debugging, in the test can fully achieve the requirements of RF
transceiver, the test process nRF24LE1 chip advantages have been fully played.
The design and implementation of wireless data transceiver based on RF transceiver
Chip Nrf24lel is detailed, and the wireless data transceiver in enhanced Sho
Ckburst TM Transceiver mode is discussed. The system realizes the long-distance
wireless data transmission of more than 50 meters in the actual outdoor test,
which can be widely used in wireless control, wireless remote control, RFID,
medical parameter detection, wireless voice, industrial control and wireless
data collection.