Data Sheet

Hartcran House, 231 Kenton Lane, Harrow, Middlesex, HA3 8RP, England
Tel: +44 (0) 20 8909 9595, Fax: +44 (0) 20 8909 2233,
Issue A, 10 April 2012
19200 baud serial wireless modem
The CLX2s a 19,200baud half-duplex serial radio
modem module operating on licence-exempt
European 433.05-434.79MHz SRD band. CLX2 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.
Figure 1: CLX2-433-19
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 19,200bps (half-duplex)
Home/Industrial Automation
Vehicle Sensor Monitoring
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: 34.5kbps NRZ FSK
UART interface: 19,200bps, 8 data bits, None Parity, None Flow Control
Supply: 3.3V at 23mA transmit, 13mA receive and <2mA standby
Transmit power: +3dBm (2mW)
Receiver sensitivity: -95dBm (for 1% BER)
32 byte data buffer
40 x 14 x 5mm
Radiometrix Ltd
CLX2 Data Sheet
page 1
Figure 2: CLX2 block diagram
Radiometrix Ltd
CLX2 Data Sheet
page 2
The radio / datastream interface
A 32 byte software FIFO is implemented in both the transmit and receive code. At the transmit end this is
used to allow for the transmitter start up time (about 4ms), while on receive it buffers arriving packets to the
constant output data rate. All timing and data formatting tasks are handled by the software. The user need
not worry about keying the transmitter before sending data: the link is entirely transparent.
For transmission across the radio link data is formatted into packets, each comprising 6 bytes of data, a
preamble sequence, a sync code and a checksum. If less than 6 bytes are in the transmit end FIFO then a
packet is still sent, but idle codes replaces the unused bytes. When the transmit end FIFO is completely
emptied, then the transmitter is keyed off .
Figure 3: CLX2 footprint (top view)
Pin description
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, 50kΩ internal pull-up
3.3V DC (externally regulated power supply)
Received Signal Strength Indicator output
(An optional pad for wire connection)
RF in/out (50Ω impedance)
RF Ground
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. The CLX2 provides a half duplex link, but 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 datastream 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.
6. A 2.2kΩ resistance is present from RF pin 1a to ground for ESD protection
Radiometrix Ltd
CLX2 Data Sheet
page 3
Condensed specifications
Frequency stability
Channel width
Number of channels
Supply Voltage
Operating temperature
Spurious radiations
Output power
TX on switching time
Modulation type
FM peak deviation
TX spurious
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
35kbps NRZ FSK
+/-90KHz (nominal)
Local Oscillator re-radiation
-95dBm (for 0.1% data error)
-50dB (±1MHz)
Data rate
Flow control
Initial start up
19,200baud, Half duplex
1 Start bit, 8 Data bits, No parity, 1 Stop bit
3V CMOS (inverted RS232 ‘0’=0V, ‘1’=3V)
32 byte FIFO
10ms from power on
Radiometrix Ltd
CLX2 Data Sheet
page 4
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.
Ultimate performance
Easy of design set-up
Immunity proximity effects
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
433 MHz = 24 turns
A. Helical antenna
Feed point 15% to 25% of total loop length
track width = 1mm
4 to 10 cm inside area
B. Loop antenna
C. Whip antenna
wire, rod, PCB-track or a combination
of these three
433 MHz = 16.4 cm total from RF pin.
Figure 4: Antenna types
Radiometrix Ltd
CLX2 Data Sheet
page 5
Radiometrix Ltd
Hartcran House
231 Kenton Lane
Harrow, Middlesex
Tel: +44 (0) 20 8909 9595
Fax: +44 (0) 20 8909 2233
[email protected]
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
Further details are available on The Office of Communications (Ofcom) web site:
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Tel: +44 (0)20 7981 3000
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Tel. +45 33896300
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[email protected]