Microcontroller for use at89lv52 controller, RF-based chip company rfwaves rfw122-m short-range wireless data communication systems; analysis of radio frequency chips rfw122-m and its interface with the microcontroller chip rfw-d100 features; gives the system?s hardware schematic diagram and software flow chart. Applied to the device for wireless data transfer protocol csma analysis, and programming in the firmware configuration to be achieved.Currently, short-range RF communication technology is a hot technology, has been widely used in practice, there are wireless local area network (wlan), Personal Area Network (pan) and short-range wireless consumer products (such as the low-speed data transmission applications, the effective range in 30 m or less). The communication technology standards ieee802.11a, hiperlan2, Bluetooth (ieee802.15.1), homerf and ieee802.11b (wifi), etc. Devices generally support these standards are high power, complex structure, higher prices, and thus not suitable for low-end products. rfwaves company launched for existing low-end market for short-range wireless communication RF communication chipsets rfw122-m, in line with the U.S. Federal Communications Commission (fcc) specifications.The system uses radio frequency chip rfw122-m and its interface with mcu chip rfw-d100, under the control of the microcontroller at89lv52 to achieve a short-range wireless data communications.A radio frequency chip rfw122-m and the interface chip rfw-d100rfw122-m is a half-duplex radio transceiver chip, using direct sequence spread spectrum (dsss) technology, wireless transceivers, integrated circuits, work center frequency of 2.44 ghz (ism band), using ask modulation, operating voltage of 2.4 ~ 3.6 v. in idle state, almost no power consumption (0.1 ?a @ vcc = 3 v). rfw122-m can add a 200 ? differential impedance antenna (antenna printed version) or other antenna with matching circuit, the conditions in the bit error rate of 10-3, the receiver sensitivity of -77 dbm. The module has three data control line, and the data i / o port is a serial digital interface. It?s wake-up time is 20 ?s, synchronized time is 1.2 ?s. Maximum data transfer rate of 1 mbps, this time working current of 33 ma.Mcu real-time processing in order to reduce the requirements of mac protocols, rfw122-m chipset provides rfw122-m interface between the chip and mcu rfw-d100. The chip in between the mcu and rfw122-m provides a parallel interface; while providing support for csma protocols. rfw-d100 uses two techniques to obtain better carrier sense capabilities: one is the rssi (radio signal strength detection), can detect any wireless transmission intensity, to avoid conflict; the other is to use rfwaves network Carrier Sense algorithm. can be avoided with the use of this technology within the network or other networks rfwaves site of conflict.(1) rssi (radio signal strength detection)rssi mechanism used to compare a non-rfwaves site transfer of power over a certain threshold (with an external resistor to set this value, rfw-d100 shows the threshold voltage and the reference formula) to compare the results put in the register ssr [7]-comp_in in. When the data transfer within the mcu, go read the register, according to the status register to determine whether the channel is occupied state to determine whether the data is transferred.(2) internal / external rfwaves network carrier sense algorithmThe mechanism is mainly used to monitor similar rfwaves network. rfwd100 monitor the use of carrier sense algorithm is similar rfwaves external network data is being transferred. If the external rfwaves ongoing data transmission network, the internal flag is set to indicate the channel is occupied state; if the channel is occupied by the state to idle state, will generate an interrupt to notify the mcu, At this point mcu data can be transmitted.2 Hardware DesignThe microprocessor system using atmel?s at89lv52. It is a series based on 51 low-power microprocessor, support assembly and c language, development environment, the company used keil keil c51 (51 microcontroller assembly language development tools and c); support assembly, c programming language, and mixed, while maintaining a powerful software simulation and hardware emulation. System consists of two half-duplex communication terminal, from the high-level data from the serial port sent to the mcu, mcu then the data is sent to the rfw-d100. rfw-d100 after the data package sent to rfw122-m modulation, and then sent through the antenna. System block diagram shown in Figure 1.
?Figure 1 System Block Diagram
mcu and rfw122-m and rfw-d100 connection shown in Figure 2.
?Figure 2 mcu and rfw122-m and the connection between rfw-d1003 communication protocols and software processesSystem uses the data link layer protocol is Carrier Sense Multiple Access Protocol (csma). LANs generally use a common method of media, for simultaneous access to multiple sites when the media, it is necessary to control. csma is the common way. When a network station to send data, the first test whether there are other sites occupied by the transmission media. Specifically: first, carrier sense, if we find the media (media) is idle, then immediately send data; Otherwise, depending on the retransmission strategy retreat.as the system of work in the 2.44 ghz ism band, the band there is a big disturbance, so the design data packet structure of the most important principle is to take the shortest possible time the channel in order to reduce the probability of potential conflicts. in transmission, the probability of packet overlap with each sending node is occupied channel time sharing proportional. therefore, if the high bit rate transmission of data packets, will increase the probability of the data is correctly received. rfw-d100 air data transfer rate up to 1 mbps, it can be configured for a variety of transmissionThis article from the Indoor Light Fixtures
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