Application of single-chip 2.4GHz wireless transceiver chip nRF24E1

Introduction
nRF24E1 is a high-speed 1Mbps single-chip wireless transceiver chip launched by Nordic Company with an embedded high-performance single-chip microcomputer core.
Compared with Bluetooth, nRF24E1 has no complex communication protocol, is completely transparent to users, and the same products can communicate freely. More importantly, nRF24E1 is cheaper than Bluetooth products and has cost advantages. Therefore, nRF24E1 is a low-cost RF system-level chip with small size, low power consumption and few peripheral components in the industry. The block diagram of

nRF24E1 wireless transceiver chip nRF24E1 is shown in Figure 1. nRF24E1 is embedded with a 2.4GHz wireless core nRF2401, with a globally open 2.4GHz frequency band and 125 channels, which can meet the needs of multi-frequency and frequency hopping. It integrates an enhanced 8051 microprocessor core, 9-channel 10-bit ADC, a sampling rate of 100kHz, built-in voltage reference, power supply detection, configurable PWM output, UART asynchronous serial port, SPI synchronous communication serial port; built-in CRC verification and multi-point communication control, suitable for point-to-multipoint communication. Using 1.9~3.6V power supply, very few peripheral circuits, all working parameters such as transmission power and working frequency are set by software. All high-frequency components including inductors and oscillators are integrated inside the chip, with good consistency, stable performance and no external influence. Moreover, each chip can set up to 40 bits of address through software, and only output data when receiving the local address (providing an interrupt indication), which is very convenient for programming. Built-in CRC error correction hardware circuit and protocol are very convenient for software developers to program. Since the error correction operation does not need to be completed by the microcontroller, the difficulty of wireless application development can be reduced. DuoCeiver technology can receive data from two nRF2401 at the same time. The basic principle is that DuoCeiver is a simultaneous dual-channel receiving mode. nRF24E1 can receive data from two 1 Mbps transmitters (for example: nRF24E1, nRF2401 or nRF2402) separated by 8MHz through an antenna interface. The outputs of the two data channels are fed back to two sets of independent interface pins: Data Channel 1: CLK1, DATA, DR1 Data Channel 2: CLK2, DOUT2, DR







Figure 1. nRF24E1 block diagram


Figure 2 DuoCeivertm simultaneous dual reception channels

DuoCeiver technology provides two independent dedicated digital channels for RX, replacing the requirement for two separate receiving systems. Figure 2 shows DuoCeiver dual receiving channels at the same time. The frequency of digital channel 2 is 8MHz higher than that of digital channel 1 to ensure normal reception.
nRF24E1 also has a high rate of 1Mbps, higher than Bluetooth, and has high data throughput. Built-in WTD watchdog with data time slot and data clock recovery.

Application circuit


Figure 3 RF circuit of nRF24E1 connected to single-ended 50W antenna

The RF circuit diagram of nRF24E1 connected to a single-ended 50W antenna is shown in Figure 3.
This circuit diagram contains all the circuits required to implement nRF24E1 in a short-range communication system. All the digital I/O signals used around the wiring diagram and the A/D inputs can be connected to the peripherals used by the user. The program code of the serial EEPROM required by nRF24E1 is included in the circuit. The EEPROM is a standard 2XX320 SPI type. The circuit has its own power supply and ground. The power supply of this part of the application circuit should be separated from any high-current peripheral power supply filtering. A different single-ended matching network is used for the single-ended 50W antenna.
The following points should be noted in actual application:
the available frequency band is determined by local adjustment;
the crystal frequency should be selected from the different values ​​specified in the five configuration tables of 4, 8, 12, 16 and 20MHz. Usually 16MHz is used when the data rate is 1Mbps;
the data rate can only be 250kbps or 1000kbps;
the load impedance of the non-embedded antenna is 400W. ■

References
1. Nordic VLSI. 2.4Ghz RF transceiver with embedded 8051 compatible microcontroller and 9 input, 10 bit ADC. 2003.7
2. Nordic VLSI. nRF24E1 and nRF24E2 RF layouts. 2003.5