Hartcran House, 231 Kenton Lane, Harrow, Middlesex, HA3 8RP, England Tel: +44 (0) 20 8909 9595, Fax: +44 (0) 20 8909 2233, www.radiometrix.com CPX2 PRELIMINARY Issue 1, 15 September 2015 2700 baud wireless packet modem The CPX2s a 2,700 baud half-duplex serial radio packet modem module operating on licenceexempt European 433.05-434.79MHz SRD band. CPX2 is an intermediate level OEM radio modem which is in between a raw FSK radio module like BiM2G and a sophisticated OEM radio modem like RPM2A. It takes care of preamble, frame synchronisation and error checking. Features Figure 1: CPX2-433.92-2k7 Conforms to EN 300 220-2 and EN 301 489-3 SAW front-end filter Small size Low cost Direct interface to microcontroller UART Serial modem baud rate at 2,700bps (half-duplex) 200m line of sight operating range Applications Home/Industrial Automation Vehicle Sensor Monitoring Telemetry Data Logging Systems Security Systems for Home/Industrial In-building environmental monitoring and control Sports and Performance Monitoring Technical Summary Operating frequency: 433.92MHz (default) Modulation: 2.7kbps NRZ FSK UART interface: 57,600bps, 8 data bits, Parity None, Flow Control None Supply: 3.3V at 23mA transmit, 13mA receive and <2mA standby Transmit power: +3dBm (2mW) Receiver sensitivity: -105dBm (for 0.1% data error) 32 byte data buffer 40 x 14 x 5mm Radiometrix Ltd CPX2 Data Sheet page 1 Figure 2: CPX2 block diagram Radiometrix Ltd CPX2 Data Sheet page 2 Operation of the CPX2 packet data transceiver The CPX2 is a variant of the basic CLX2 data link device, using the same hardware but achieving considerably greater range (albeit at the cost of a lower aggregate data rate). On the other hand, Its user interface data rate is considerably faster (57,600 baud) to minimise data transfer time overhead to and from the module, so in some applications the CPX2 will actually exhibit better efficiency. While a standard CLX2 will reliably receive a -95dBm signal, the CPX2 is reliably seen to recover packets at signal levels of -105dBm and less (corresponding to around twice the range). The CPX2 is not a transparent modem. It cannot handle constant streaming data. All timing and data formatting tasks are handled by the software. The user need not worry about keying the transmitter before sending data. For transmission across the radio link data is formatted into packets, each comprising data bytes, preamble sequence, frame synchronisation code and checksum. It sends its data in discrete 32 byte blocks, and while it is sending a block it cannot do anything else. A 32 byte block (or "packet") takes about 150ms to send (during which the RF carrier is 'on' for 140ms) The unit idles in receive. If a valid RF packet is detected, then it is immediately decoded and outputted as a stream of serial data bytes (start bit following preceding stop bit) If data is presented to a unit's TXD pin, the first byte received initiates the transmit process. The unit will immediately switch its RF circuits from receive to transmit and start loading any available transmit data into its buffer. It will carry on loading the buffer until either: 1. 32 bytes are received, or 2. A gap of 5ms is seen following a byte. At this point the unit pulls the active low TXON pin low and begins modulating its carrier (by now stabilised and at full power) with the coded data packet. Any "extra" bytes beyond the first 32 are discarded. Once the burst has been transmitted, the transmitter turns off and TXON is returned to the high state. In the absence of a valid signal, the CPX2 (in idle/receive) uses framer and checksum data to avoid outputting random garbage. Similarly, at the edge of the range or in the presence of interference the unit will either output complete, correct data blocks or nothing at all (it is very unlikely to ever output a corrupted block) Pulling the /RXOFF pin low (against its internal pull-up) puts the unit into standby (as on the CLX2) Figure 3: CPX2 footprint (top view) Radiometrix Ltd CPX2 Data Sheet page 3 Pin description Pin 1 2 3 4 Name GND RXD TXD /TXON /RXOFF 5 VDD RSSI Function Ground Received Data output at 3V UART (inverted RS232) level Transmit Data input at 3V UART (inverted RS232) level [No pull-up] /TXON Active low Transmitter ON indicator Output [Transmit Mode] /RXOFF Active low Receiver hot Standby Input [Receive Mode] Open drain, 50k internal pull-up 3.3V DC (externally regulated power supply) Received Signal Strength Indicator output (An optional pad for wire connection) RF in/out (50 impedance) RF Ground 1a RF 2a RFGND Notes: 1. TXD has no internal pull-up. If the unit is used in Receive only mode, tie this pin to VCC 2. VDD must be a clean 3.3V DC regulated supply 3. The STATUS pin. In transmit, this pin pulls low if the device is transmitting a data packet. On receive it floats high. If pulled low in receive, the unit goes into hot standby (<2mA) In standby the unit does not receive, but will go into transmit if valid data is presented to TXD. 4. TXD / RXD are inverted RS232 at 3V CMOS levels. To connect to a true RS232 device, inverting level shifters must be used (e.g. MAX232 type are ideal, but simple NPN transistor switches with pull-ups often suffice). With typical microcontrollers and UARTs, direct connection is possible. 5. Because CPX2 provides a lower 2,700 baud half duplex radio link with higher 57,600 user baud rate, no more than 32 bytes should be uploaded at a time. i.e. data cannot be streamed. 6. Provided no two devices attempt to transmit at one time, then no further restrictions on data transmission need be made, as all transmit timing, valid data identification and data byte buffering is conducted by the unit. There is no 'transmit enable' pin. Synchronisation and framing words in the packet prevent the receiver outputting garbage in the absence of signal or presence of interference. 7. A 2.2k resistance is present from RF pin 1a to ground for ESD protection Radiometrix Ltd CPX2 Data Sheet page 4 Condensed specifications Frequency Frequency stability Channel width Number of channels Supply Voltage Current Operating temperature Spurious radiations Interfaces User RF Size Transmitter Output power TX on switching time Modulation type FM peak deviation TX spurious 433.92MHz ±10kHz 250kHz 1 3.3V DC 23mA transmit 13mA receive/ <2mA standby -20°C to +55°C (Storage -30°C to +70°C) Compliant with ETSI EN 300 220-2 and EN 301 489-3 5pin 0.1" pitch molex (pin 6 absent) 2pin 0.1" pitch molex 40 x 14 x 5mm 2mW ±1dB <4ms 2.7kbps NRZ FSK +/-30kHz (nominal) <-36dBm Receiver Sensitivity Blocking Local Oscillator re-radiation -105dBm (for 0.1% data error) -50dB (±1MHz) <-57dBm Interface Data rate Format Levels Buffers Flow control Initial start up 57,600baud, Half duplex 1 Start bit, 8 Data bits, No parity, 1 Stop bit 3V CMOS (inverted RS232 ‘0’=0V, ‘1’=3V) 32 byte FIFO None 10ms from power on Radiometrix Ltd CPX2 Data Sheet page 5 Antenna requirements Three types of integral antenna are recommended and approved for use with the module: A) Whip This is a wire, rod ,PCB track or combination connected directly to RF pin of the module. Optimum total length is 16cm (1/4 wave @ 433MHz). Keep the open circuit (hot) end well away from metal components to prevent serious de-tuning. Whips are ground plane sensitive and will benefit from internal 1/4 wave earthed radial(s) if the product is small and plastic cased B) Helical Wire coil, connected directly to RF pin, open circuit at other end. This antenna is very efficient given it’s small size (20mm x 4mm dia.). The helical is a high Q antenna, trim the wire length or expand the coil for optimum results. The helical de-tunes badly with proximity to other conductive objects. C) Loop A loop of PCB track tuned by a fixed or variable capacitor to ground at the 'hot' end and fed from RF pin at a point 20% from the ground end. Loops have high immunity to proximity detuning. A whip *** *** * * Ultimate performance Easy of design set-up Size Immunity proximity effects B helical ** ** *** ** C loop * * ** *** The antenna choice and position directly controls the system range. Keep it clear of other metal in the system, particularly the 'hot' end. The best position by far, is sticking out the top of the product. This is often not desirable for practical/ergonomic reasons thus a compromise may need to be reached. If an internal antenna must be used, try to keep it away from other metal components, particularly large ones like transformers, batteries and PCB tracks/earth plane. The space around the antenna is as important as the antenna itself. 0.5 mm enameled copper wire close wound on 3.2 mm diameter former RF 433 MHz = 24 turns A. Helical antenna Feed point 15% to 25% of total loop length RF-GND track width = 1mm 2 C2 C3 C4 C1 4 to 10 cm inside area RF B. Loop antenna 16.4cm C. Whip antenna wire, rod, PCB-track or a combination of these three RF 433 MHz = 16.4 cm total from RF pin. Figure 4: Antenna types Radiometrix Ltd CPX2 Data Sheet page 6 Radiometrix Ltd Hartcran House 231 Kenton Lane Harrow, Middlesex HA3 8RP ENGLAND Tel: +44 (0) 20 8909 9595 Fax: +44 (0) 20 8909 2233 [email protected] www.radiometrix.com Copyright notice This product data sheet is the original work and copyrighted property of Radiometrix Ltd. Reproduction in whole or in part must give clear acknowledgement to the copyright owner. Limitation of liability The information furnished by Radiometrix Ltd is believed to be accurate and reliable. Radiometrix Ltd reserves the right to make changes or improvements in the design, specification or manufacture of its subassembly products without notice. Radiometrix Ltd does not assume any liability arising from the application or use of any product or circuit described herein, nor for any infringements of patents or other rights of third parties which may result from the use of its products. This data sheet neither states nor implies warranty of any kind, including fitness for any particular application. These radio devices may be subject to radio interference and may not function as intended if interference is present. We do NOT recommend their use for life critical applications. The Intrastat commodity code for all our modules is: 8542 6000 R&TTE Directive After 7 April 2001 the manufacturer can only place finished product on the market under the provisions of the R&TTE Directive. Equipment within the scope of the R&TTE Directive may demonstrate compliance to the essential requirements specified in Article 3 of the Directive, as appropriate to the particular equipment. Further details are available on The Office of Communications (Ofcom) web site: http://stakeholders.ofcom.org.uk/spectrum/technical/rtte/ Information Requests Ofcom Riverside House 2a Southwark Bridge Road London SE1 9HA Tel: +44 (0)20 7981 3000 Fax: +44 (0)20 7981 3333 www.ofcom.org.uk European Radiocommunications Office (ERO) Peblingehus Nansensgade 19 DK 1366 Copenhagen Tel. +45 33896300 Fax +45 33896330 [email protected] www.ero.dk