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CYWUSB6935: WirelessUSB LR 2.4-GHz DSSS Radio SoC
The document introduces the WirelessUSB technology and the CYWUSB693 WirelessUSB transceiver chip. It provides an overview of WirelessUSB and how it compares to other wireless technologies like Bluetooth and Zigbee. It then describes the key features of the CYWUSB6935 chip such as its 2.4GHz radio, data throughput, and integrated components. Finally, it outlines some potential applications for WirelessUSB technology and provides a functional description and block diagram of the CYWUSB6935 chip.
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CYWUSB6935: WirelessUSB LR 2.4-GHz DSSS Radio SoC
- 1. CYWUSB6935: WirelessUSB LR 2.4-GHz DSSS Radio SoC Source: Cypress Semiconductor
- 2. Introduction Purpose This training module introduces the WirelessUSB technology and CYWUSB693 WirelessUSB transceiver. Outline Introduction of the WirelessUSB technology Difference between WirelessUSB and different Techniques. Features of CYWUSB6935 device. Functional block diagram and functional overview Application Example. Content 20 pages
- 3. WirelessUSB Market PositioningProprietary 27MHz/900MHz ZigBee networking solution for home/industrial automation Simple Point-to-Point wireless solution BT Short-range networking solution Long-range networking solution 802.11 Cost / Complexity Strategy:make WirelessUSB the defacto standard for multi-point to point wireless Networking Wire Replacement UWB Short-range, high-speed networking solution RFID Tags WirelessUSB TM Simple Multipoint-to-Point solution Active/Passive Tags for inventory tracking
- 4.
- 5. WirelessUSB vs. 27MHzWirelessUSB is a higher quality solution 10M range for home and conference room use Virtually unlimited co-location for office and classroom use Bi-Directional for better security and robustness Bandwidth for many devices (KBM, Remote, Joystick etc.) WirelessUSB has Comparable Cost WirelessUSB is on a silicon cost reduction path Integration of MCU+radio in development 2.4GHz is bigger than 27MHz Real and perceived advantage (e.g. cordless telephones) WirelessUSB is designed to replace 27MHz systems
- 6. WirelessUSB vs. BluetoothBluetooth is a poor solution for HID Bluetooth designed for cell-phone usage model Assumes frequent recharging, roaming, ad-hoc networking Results in poor battery life or forces rechargeable solutions Complex installation results in high support cost Use of BT network (printing, syncing) reduces KBM performance WirelessUSB costs less and performs better All the benefits of 2.4GHz approaching 27MHz prices Installation is plug and play No confusing driver support and interoperability issues Bluetooth has issues with interference and co-location BT 1.2 helps interference, but makes co-location worse Bluetooth not well suited for remote control devices
- 7. Features of CYWUSB69352.4-GHz radio transceiver. Operates in the unlicensed Industrial, Scientific, and Medical (ISM) band (2.4 GHz–2.483 GHz). – 95-dBm receive sensitivity. Up to 0dBm output power. Range of up to 50 meters or more. Data throughput of up to 62.5 Kbits/sec. Highly integrated low cost, minimal number of external components required. Dual DSSS reconfigurable baseband correlators. SPI microcontroller interface (up to 2-MHz data rate). 13-MHz input clock operation. Low standby current < 1 μA. Integrated 30-bit Manufacturing ID. Operating voltage from 2.7V to 3.6V.
- 8. Applications Building/Home AutomationClimate Control Lighting Control Smart Appliances On-Site Paging Systems Alarm and Security Industrial Control Inventory Management Factory Automation Data Acquisition Automatic Meter Reading (AMR) Transportation Diagnostics Remote Keyless Entry Consumer / PC Locator Alarms Presenter Tools Remote Controls Toys
- 9. Functional Description ofCYWUSB6935 The CYWUSB6935 transceiver is a single-chip 2.4-GHz Direct Sequence Spread Spectrum (DSSS) Gaussian Frequency Shift Keying (GFSK) baseband modem radio that connects directly to a microcontroller via a simple serial peripheral interface.
- 10. Block Diagram ParametersGFSK Modem: The transmitter uses a DSP-based vector modulator to convert the 1-MHz chips to an accurate GFSK carrier. The receiver uses a fully integrated Frequency Modulator (FM) detector with automatic data slicer to demodulate the GFSK Signal. Dual DSSS Baseband: Data is converted to DSSS chips by a digital spreader. De-spreading is performed by an oversampled correlator. The DSSS baseband cancels spurious noise and assembles properly correlated data bytes. The DSSS baseband has three operating modes: 64-chips/bit Single Channel, 32-chips/bit Single Channel, and 32-chips/bit Single Channel Dual Data Rate.
- 11. Block Diagram ParametersSerializer/Deserializer (SERDES): The SERDES provides byte-level framing of transmit and receive data. Bytes for transmission are loaded into the SERDES and receive bytes are read from the SERDES via the SPI interface. The SERDES provides double buffering of transmit and receive data. Application Interfaces: CYWUSB6935 has a fully synchronous SPI slave interface for connectivity to the application MCU. Configuration and byte-oriented data transfer can be performed over this interface. An interrupt is provided to trigger real time events. An optional SERDES Bypass mode (DIO) is provided for applications that require a synchronous serial bit-oriented data path.
- 12. DSSS and PNCode DSSS = Direct Sequence Spread Spectrum DSSS generates a bit pattern for each data bit to be transmitted WirelessUSB uses a 32 or 64-chip “pattern” also known as PN Code PN Code = Pseudo Noise Code A very distinct 32 or 64-chip binary signal For every data bit to be transmitted, a 32 or 64-chip PN Code is produced
- 13. For illustration purposes,a 10-bit PN Code is used in the example diagram WirelessUSB uses 32 or 64-bit PN Codes The PN Code is transmitted at a much higher frequency than the data bit; therefore, it appears as random noise PN Code
- 14. 1 Bit Transmissionusing a 64 bit PN Code
- 15. RSSI RSSI =Receive Signal Strength Indicator Determine the connection quality Determine the value of the noise floor Check for a quiet channel before transmitting. A 5-bit field of the read-only REG_RSSI Register inside the radio indicates the strength of the received signal The higher values indicating stronger received signals If the RSSI value is too high, interference is the most likely cause, so the WUSB system tries to find a quieter channel to operate in In a WirelessUSB system, only the “Dongle” monitors RSSI
- 16. Avoiding Interference 24002404 2408 2412 2420 2424 2428 2416 Close range Wi-Fi signal may interfere with your 2.4GHz device Interference detected due to increased error rates Free channel found Frequency (MHz) The key to avoiding interference is detecting it Receive Signal Strength Indicator High signal strength ( RSSI ) detected here, so search continues
- 17. Application Examples CYWUSB6935Battery Powered Device
- 18. MCU Interface Sequence Diagrams
- 19. Application: WirelessUSB LRAlarm System WirelessUSB LR Alarm System
- 20. Additional Resource Forordering the CYWUSB6935, please click the part list or Call our sales hotline For additional inquires contact our technical service hotline For more product information go to http://www.cypress.com/products/?gid=14&fid=65&rpn=CYWUSB6935 Newark Farnell
Editor's Notes
- #3 Welcome to the training module on Cypress CYWUSB6935: WirelessUSB LR 2.4-GHz DSSS Radio SoC. This training module introduces the WirelessUSB technology and CYWUSB693 WirelessUSB transceiver.
- #4 Wireless technologies have gained rapid acceptance in the marketplace and the growth continues to accelerate. The ability to move data without having to connect a cable, run wires, or worry about having the right adapters is very appealing. Wireless offers the promise of convenience, speed, and ease of use. Wireless is still all about moving information from point A to point B. Depending upon the needs of the application, data may move in one direction only, or it might need to move in both directions. There are many different wireless technologies in use or emerging today. Examples include WiFi®, Bluetooth®, ZigbeeTM, Ultra-Wide Band (UWB), and many more.
- #5 These technologies differ in many ways, such as frequency spectrum, data rates, data encoding, protocols, network topologies, and others. The Cypress WirelessUSB and PRoC products are aimed at mid to low data rates (up to 1 Mbps) and simple cable replacement or simple network topologies. WirelessUSB only supports moving data in one direction at a time, thus it is half duplex.
- #6 Here gives the difference between WirelseeUSB and 27MHz technology.
- #7 Here introduces the difference between WirelseeUSB and Bluetooth technology method.
- #8 The CYWUSB6935 provides a complete SPI-to-antenna radio modem. The CYWUSB6935 is designed to implement wireless devices operating in the worldwide 2.4-GHz Industrial, Scientific, and Medical (ISM) frequency band (2.400 GHz–2.4835 GHz). The CYWUSB6935 contains a 2.4-GHz radio transceiver, a GFSK modem, and a dual DSSS reconfigurable baseband. The radio and baseband are both code- and frequency-agile. Forty-nine spreading codes selected for optimal performance (Gold codes) are supported across 78 1-MHz channels yielding a theoretical spectral capacity of 3822 channels. The CYWUSB6935 supports a range of up to 50 meters or more.
- #9 Here shows overall areas where this device can be used. This device will fit into more or less every areas where we require wireless connectivity with suitable Data rate. It can go into Home/Building Automation, Industrial Control, Meter Reading, Consumer applications like remote, toys, locator alarm, presenter tool, etc.
- #10 The CYWUSB6935 transceiver is a single-chip 2.4-GHz Direct Sequence Spread Spectrum (DSSS) Gaussian Frequency Shift Keying (GFSK) baseband modem radio that connects directly to a microcontroller via a simple serial peripheral interface. As stated previously, the CYWUSB6935 contains a 2.4-GHz radio transceiver, a GFSK modem, and a dual DSSS reconfigurable baseband. The radio and baseband are both code- and frequency-agile. Forty-nine spreading codes selected for optimal performance (Gold codes) are supported across 78 1-MHz channels yielding a theoretical spectral capacity of 3822 channels. The CYWUSB6935 supports a range of up to 50 meters.
- #11 This transmitter uses a DSP-based vector modulator to generate an accurate GFSK carrier. The receiver uses a fully integrated Frequency Modulator (FM) detector with automatic data slicer to demodulate the GFSK signal. Data is converted to DSSS chips by a digital spreader. De-spreading is performed by an oversampled correlator. The DSSS baseband cancels spurious noise and assembles properly correlated data bytes. The DSSS baseband has three operating modes: 64-chips/bit Single Channel, 32-chips/bit Single Channel, and 32-chips/bit Single Channel Dual Data Rate (DDR).
- #12 The CYWUSB6935 provides a data Serializer/Deserializer (SERDES), which provides byte-level framing of transmit and receive data. Bytes for transmission are loaded into the SERDES and receive bytes are read from the SERDES via the SPI interface. The SERDES provides double buffering of transmit and receive data. While one byte is being transmitted by the radio the next byte can be written to the SERDES data register insuring there are no breaks in transmitted data. CYWUSB6935 has a fully synchronous SPI slave interface for connectivity to the application MCU. Configuration and byte-oriented data transfer can be performed over this interface. An interrupt is provided to trigger real time events.
- #13 WirelessUSB LS utilizes a 2.4-GHz direct sequence spread spectrum (DSSS) radio interface. DSSS generates a redundant bit pattern for each bit to be transmitted. This bit pattern is called a “chip” or a pseudo noise code. Because they use direct sequence spread spectrum (DSSS) technology, WirelessUSB systems encode their data within Pseudo Noise (PN) codes. The main advantage is to increase the robustness and recoverability of the signal in the presence of interference. A simple explanation is that a single data bit from the application is represented by multiple bits when sent across the air, and decoded back into the original data bit on the other side. One result of using PN codes is that devices in a given network must agree to use a common PN code in order to understand one another. Another advantage of this is that it increases the co-location capabilities since devices can share the same channel if they use different PN Codes.
- #14 The pseudo noise code is a binary signal that is produced at a much higher frequency than the data that is to be transmitted. Because it has a higher frequency, it has a large bandwidth that spreads the signal in the frequency domain. The nature of this signal makes it appear that it is random noise. The wide bandwidth provided by the pseudo noise code allows the signal power to drop below the noise threshold without losing any information. This allows DSSS signals to operate in noisy environments and reduces the interference caused by traditional narrowband signals.
- #15 In the presence of interference, the transmitted PN code will often be received with some PN-code chips corrupted. The receivers use a data correlator to decode the incoming data stream. If the number of chip errors is less than the correlator error threshold, the data will be correctly received. Otherwise, the data bit will be marked as “unknown” and the software error recovery mechanism will be used to recover the “unknown” data. In the WirelessUSB protocol, PN Code is a one-byte number index to the gold code table. Changing the receiver’s PN Code is equivalent to changing the 32-chip or 64-chip “pattern” that the receiver is trying to look for.
- #16 The RSSI register (Reg 0x22) returns the relative signal strength of the ON-channel signal power and can be used to determine the connection quality, determine the value of the noise floor, and check for a quiet channel before transmitting. The internal RSSI voltage is sampled through a 5-bit analog-to-digital converter (ADC). The conversion produces a 5-bit value in the RSSI register along with a valid bit. Once a connection has been established, the RSSI register can be read to determine the relative connection quality of the channel. To check for a quiet channel before transmitting, first set up receive mode properly and read the RSSI register. Then, wait greater than 50 μs and read the RSSI register again. Next, clear the Carrier Detect Register and turn the receiver OFF. A RSSI register value of 0-10 indicates a channel that is relatively quiet. A RSSI register value greater than 10 indicates the channel is probably being used. A RSSI register value greater than 28 indicates the presence of a strong signal.
- #17 The ISM band is a busy spectrum with a lot of different technologies sharing the band. Therefore, managing interference is an important consideration. The DSSS technology itself is the first stage of managing interference. In the presence of stronger interference, the DSSS technology by itself may not be enough to overcome interference. There are another mechanism for overcoming interference. The first is detecting the interference, which can be accomplished by monitoring the background noise level using the measurement of signal strength. Once interference has been detected, the system must then identify a channel with an acceptable level of interference, and then move all nodes on the system to this new channel.
- #18 This slide shows a block diagram example of a typical battery powered device using the CYWUSB6935 chip. The CYWUSB6935 uses the four-wire SPI to communicate with an application MCU.
- #19 This diagram shows MCU interface with this wirelessusb device and its sequence. The four-wire SPI communications interface consists of Master Out-Slave In (MOSI), Master In-Slave Out (MISO), Serial Clock (SCK), and Slave Select (SS). The SPI receives SCK from an application MCU on the SCK pin. Data from the application MCU is shifted in on the MOSI pin. Data to the application MCU is shifted out on the MISO pin. The active-low Slave Select (SS) pin must be asserted to initiate a SPI transfer.
- #20 This figure shows the application schematic using this device as networked connected device (i.e. one master and many slave devices connected).
- #21 Thank you for taking the time to view this presentation on CYWUSB6935 . If you would like to learn more or go on to purchase some of these devices, you may either click on the part list link, or simple call our sales hotline. For more technical information you may either visit the Cypress site, or if you would prefer to speak to someone live, please call our hotline number, or even use our ‘live chat’ online facility.