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 de
6、tected 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 addi
7、tion, 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 MC
9、U 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 co
10、ntrol 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 dragg
12、ed 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,
13、send 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 communica
14、tion, 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
16、said 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 worki
17、ng 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 va
19、lid 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 ad
20、dress 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 can be diverted to its standby mode through the SPI bus from receiving data in the register read out effective data.
