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1、NRF905 is the Nordic company introduced single-chip RF transceiver 5 mm, working in the 433 / 868 / 915 MHz three ISM channels (free of charge). NRF905 can automatically complete the processing of prefix and CRC (cyclical redundancy check), can be done automatically on-chip hardware Manchester encod
2、ing / decoding, the use of SPI communication with a microcontroller interface, configuration is very convenient. Its very low power consumption, -10dBm output power when it was launched only 11mA current, the current in the receiving mode is 12.5mA. NRF905 non-real-time data transmission methods, na
3、mely, a data transmitter, receiver received after the first items on-chip memory, outside the MCU can chip in when necessary and then to fetch. There are two operating modes and two energy-saving modes, respectively idle mode, standby mode, ShockBurst TM receive mode and sent Shock2Burst TM mode. Se
4、veral models from the outside world by controlling the CPU nRF905 the three-pin PWR_UP, TRX_CE TX_ EN and the high low to decide, PWR_UP TRX_CE TX_EN mode RF delivery mode SPI bus outside MCU configuration nRF905 through the internal registers, read and write data to their home or for standby power-
5、down mode. NRF905 power consumption in standby mode for 40 A in power-down mode, power consumption is 2.5 A.nRF905 state output nRF905 a three-pin output for the state, namely: CD (Carrier Detection), AM (address matching) and DR (data ready), are high-effective. NRF905 in a receive mode, if the det
6、ected frequency of the receiver Carrier, home CD for high detection carrier then address bytes in the data, and if their address has been configured to receive the same, higher home AM; if detected receive data in the CRC check it correctly, the effective storage data byte, home to high-DR. In addit
7、ion, the nRF905 there is a clock output pin uPCLK for users choose to use. By configuring the internal registers, can change its output frequency, which is useful for debugging. Wireless systems need at least one or two devices in one, and if there are problems when debugging is hard to judge which
8、side of the fault. May amend nRF905 register with oscilloscope observation uPCLK whether changes in output, to determine its hardware circuit and the CPU operating nRF905 procedures is correct, and thus judged the equipment is working properly. nRF905 data interfaces SPI bus through the external MCU
9、 configuration nRF905 the internal registers and send and receive data. NRF905 SPI bus, including four-pin: CSN (SPI enable), SCK (SPI clock), MISO (all from the Lord) and MOSI (from the main links). NRF905 here from the plane, the SPI clock with a wide range from 1 Hz to 10 MHz, the MCU written con
10、trol procedures need not expect the accuracy of the time. SPI bus each operation must be in order to pin the falling edge of CSN, CSN low effective, the data bus of the clock rising edge effectively. MCU on the SPI bus operators either two ways: reading and writing. During read operation, the first
11、CSN buy low, and then MOSI data online.Reading said that the output of a command byte at the same time, nRF905 in MI2SO online data output a byte of data that state information, and then output a byte address, valid data follow behind. Written in relatively simple operation, the MCU first CSN dragge
12、d down, and then write out an order online MOSI bytes and bytes of data can be. nRF905 register allocation .NRF905 register within five categories: First, RF configuration register, a total of 10 bytes, including the center frequency, wireless transmitter power configuration, receiver sensitivity, s
13、end and receive data bytes effective, receiving address configuration, and other important information is sent two data register, a total of 32 bytes, the MCU to the field of data need to write here; Third, it is sent addresses, a total of four bytes, a transceiver equipment to the normal communicat
14、ion, it is necessary to send the address of the transmitter and receiver end of the receiving address configuration the same four is receiving data register, a total of 32 bytes, nRF905 receive data on the effective storage in these registers, the MCU can be read here when necessary; 5 is the state
15、register, a byte containing address matching and data ready information, not general. MCU to operate the register, to follow the provisions of the operation nRF905 order, the following commonly used seven kinds are a byte: write RF configuration, Reading RF configuration with four binary bit, byte s
16、aid from the beginning of which read bytes, sent written data (H 20), Reading sent the data (21 H), write sent Address (22H), Reading sent Address (H 23) and receiving reading Data (24 H). For more information on the register can see nRF905 data sheet. nRF905 the working process.NRF905 normal workin
17、g before MCU should be required to write configuration registers, or in accordance with the default configuration. Subsequent work is primarily twofold: send data and receive data. When data is transmitted, the MCU should be placed in standby mode first nRF905 (PWR_UP pin high, low TRX_CE pin), and
18、then sent through the SPI bus to the address and data to be sent into the corresponding registers, after the nRF905 placed sent mode (PWR_UP, TRX_CE and TX_EN Whole home high), the data is automatically sent out by the antenna. If the RF configuration registers in the auto-bit (AUTO_RETRAN) as a val
19、id data packet will be repeated has been the outward until the MCU TRX_CE lowered, the model sent out so far. In order to more reliable data transmission, the proposed multi-use of such methods. Receive data, the MCU in the nRF905 first in the standby mode configuration of the RF receiver in the add
20、ress register write, and then their home in the receive mode(PWR_UP = 1, TRX_CE = 1, TX_EN = 0), nRF905 will automatically receive the air carrier. If the addresses match, and received the correct effective data validation, DR pin will automatically buy high, the MCU in the detection of this signal
21、can be diverted to its standby mode through the SPI bus from receiving data in the register read out effective data. 待添加的隐藏文字内容2nRF905是Nordic挪威公司推出的单片射频收发器，工作于 433/868/915 MHz 3个ISM频道(可以免费使用)。nRF905可以自动完成处理字头和CRC(循环冗余码校验)的工作，可由片内硬件自动完成曼彻斯特编码/解码，使用SPI接口与微控制器通信，配置非常方便。其功耗非常低，以-10dBm的输出功率发射时电流只有11mA，在接
22、收模式时电流为12.5mA。nRF905传输数据时为非实时方式，即发送端发出数据，接收端收到后先暂存于芯片存储器内，外面的MCU可以在需要时再到芯片中去取。nRF905一次的数据传输量最多为32 B。nRF905片内集成了电源管理、晶体振荡器、低噪声放大器、频率合成器、功率放大器、通信协议控制等模块，曼彻斯特编码/解码由片内硬件完成，无需用户对数据进行曼彻斯特编码，因此使用非常方便。nRF905有两种工作模式和两种节能模式。两种工作模式是ShockBurstTM接收模式和ShockBurstTM发送模式，两种节能模式分别是关机模式和空闲模式。nRF905的工作模式由TRX-CE、TX-EN和P
23、WR-UP三个引脚决定。由于nRF905具有ShockBurstTM功能，使得nRF905不需要使用昂贵的高速微控制处理器对数据处理/时钟恢复，也能达到较高的数据率。通过在芯片上将所有的高速信号处理变为射频通信协议，nRF905芯片提供了一个具有微控制器能力的SPI接口，数据率由具有微控制器功能的接口速率自行设定。收发电路的数字部分是一个低速率电路，而收发电路的射频链接却是一个处于最高速率的电路，整个电路要通过变速才能解决速率上的差异。nRF905芯片的ShockBurstTM模式减少了 在这一过程中的平均电流消耗。在ShockBurstTM RX模式中，当一个有效地址的数据包被接收时，能够通
24、过AM和R两个信号外送给MCU 。在ShockBurstTMTX模式中，nRF905芯片自动地完成报头的生成和CRC校验，当发送过程完成后，能够通过DR信号外送给MCU，发送工作已经完成。这样可以降低MCU对内存的要求，使得MCU实现了低成本，同时也缩短了软件的开发周期. nRF905的工作模式及设置。nRF905 有两种工作模式和两种节能模式，分别为掉电模式、待机模式、ShockBurst TM接收模式和Shock2Burst TM发送模式。这几种模式由外界CPU通过控制nRF905的3个引脚PWR_UP、TRX_CE 和TX_ EN的高低电平来决定，外界MCU通过SPI总线配置nRF905
25、的内部寄存器，读写数据时必须把其置为待机或掉电模式。nRF905在待机模式时功耗为40A ,在掉电模式时功耗为2.5A。nRF905的状态输出nRF905有3个引脚用于状态输出，分别是：CD(载波检测)、AM(地址匹配)和DR(数据就绪)，均为高电平有效。nRF905在处于接收模式时，若检测到接收频率段的载波，就置CD为高；接着检测载波数据中的地址字节，若与本身已配置的接收地址相同，则置AM为高;若再检测到接收数据中的CRC校验正确，则存储有效数据字节，置DR为高。此外，nRF905还有一个时钟输出引脚uPCLK，供用户选择使用。通过配置内部寄存器，可改变其频率输出，这一点在调试时很有用。无线
26、系统至少需要一发一收两个设备，调试时若出现问题很难判断是哪一方的故障。可以通过修改 nRF905的寄存器，用示波器观察uPCLK输出是否变化的方法，来判断其硬件电路和CPU操作nRF905的程序是否正确，从而判断该设备是否工作正常。nRF905 的数据接口。外围MCU通过SPI总线配置nRF905的内部寄存器和收发数据。nRF905的SPI总线包括4个引脚：CSN(SPI 使能)、SCK(SPI时钟)、MISO(主入从出)和MOSI(主出从入)。这里nRF905为从机，其SPI的时钟范围很宽，可以从1Hz10MHz，因此MCU在写控制程序时不必苛求时间的准确度。SPI总线的每次操作都必须在使能
27、引脚CSN的下降沿开始，CSN低电平有效，总线上的数据在时钟的上升沿有效。MCU对SPI总线的操作不外乎两种方式：读和写。在进行读操作时，先把CSN置低，然后在 MOSI 数据线上输出一个表示读命令的字节，与此同时，nRF905会在MISO数据线上输出一字节表示状态信息的数据，随后输出一地址字节，后面跟随有效数据。在进行写操作时比较简单，MCU先把CSN拉低 ,然后在MOSI线上输出写命令字节和数据字节即可。nRF905 的寄存器配置。nRF905 内部有5类寄存器：一是射频配置寄存器，共10个字节，包括中心频点、无线发送功率配置、接收灵敏度、收发数据的有效字节数、接收地址配置等重要信息；二是
28、发送数据寄存器，共32字节，MCU 要向外发的数据就需要写在这里；三是发送地址，共4个字节，一对收发设备要正常通信，就需要发送端的发送地址与接收端的接收地址配置相同；四是接收数据寄存器，共32字节，nRF905接收到的有效数据就存储在这些寄存器中，MCU 可以在需要时到这里读取；五是状态寄存器，1个字节，含有地址匹配和数据就绪的信息，一般不用。MCU若要操作这些寄存器，需遵循nRF905规定的操作命令，常用的有以下7种，都是1个字节；写射频配置(0XH“X”含4位二进制位，该字节表示要开始写的初始字节数)、读射频配置(1XH“X”含4位二进制位，该字节表示要从哪个字节开始读)、写发送数据(20
29、H)、读发送数据(21H)、写发送地址(22H)、读发送地址(23H)和读接收数据(24H) 。nRF905 的工作过程。nRF905 在正常工作前应由MCU先根据需要写好配置寄存器，或是按照默认配置工作。其后的工作主要是两个：发送数据和接收数据。发送数据时，MCU应先把nRF905置于待机模式(PWR_UP引脚为高、TRX_CE 引脚为低)，然后通过SPI总线把发送地址和待发送的数据都写入相应的寄存器中，之后把nRF905置于发送模式(PWR_UP、TRX_CE和TX_EN全置高)，数据就会自动通过天线发送出去。若射频配置寄存器中的自动重发位设为有效，数据包就会重复不断地一直向外发，直到MCUTRX_CE 拉低，退出发送模式为止。为了数据更可靠地传输，建议多使用此种方式。接收数据时，MCU先在nRF905 的待机模式中把射频配置寄存器中的接收地址写好，然后置其于接收模式，nRF905 就会自动接收空中的载波。若收到地址匹配和校验正确的有效数据，DR 引脚会自动置高，MCU在检测到这个信号后，可以改其为待机模式，通过SPI总线从接收数据寄存器中读出有效数据。
