Data Sheet

Hartcran House, 231 Kenton Lane, Harrow, HA3 8RP, England
Issue 1, 21 May 2009
Tel: +44 (0) 20 8909 9595, Fax: +44 (0) 20 8909 2233
UHF Multi Channel Radio Modem
The TDM2 is a very simple 433MHz
band radio data modem. It provides a
transparent data link between a pair
of 9600 baud RS232 ports without any
additional interface circuitry.
The TDM2 is a TDL2A radio module,
combined with suitable interface circuits,
power supplies and connectors, packaged in
an attractive instrument case. In the
simplest case, a pair of 'box modems' (with
suitable aerials and power supplies
connected, of course) can be connected
directly to the serial ports of a pair of
industrial PCs and the resulting wireless
Figure 1: TDM2-433-9
data link used without any further installation or programming.
Range of Features
RS232 driver and DB9F connector for direct interface to PC serial port
Serial modem baud rate at 9600bps (half-duplex)
Addressable point-to-point
5 serial select wideband channels (in the 433.05 – 434.79MHz European band)
Carries ASCII and RTU MODBUS messages
Access to internal diagnostic/Test modes using HyperTerminal
On board SMA antenna connector
Signal LED for visual indication of valid code received
Setup is simple as Plug-and-Play
Set-up and configuration using HyperTerminal
Conforms to EN 300 220-3 and EN 301 489-3
Size: 94 x 107 x 33mm (excluding connectors)
Handheld / portable terminals
PDAs, organisers & laptops
Industrial telemetry and telecommand
In-building environmental monitoring and control
Remote data acquisition system, data logging
Fleet management, vehicle data acquisition
Radiometrix Ltd
TDM2 RF Modem Manual
Page 1
1 2 3 4
Figure 2: TDM2 (rear view)
Looked at from the outside, the TDM2 presents:
9 way D-type
SMA RF connector
2.1mm power jack
4 way DIP switch
RS232 port
External power (9-15v)
Mode selection (see later)
(all on the rear of the case)
Slide switch
Internal battery 'on/off'
(in a recess, on the side of the case)
Three LED indicators
Power on
Valid data receiving
(green, on the left)
(red, in the middle)
(red, on the right)
Powering the TDM: The TDM2 radio modem requires a source of energy to operate. There are
several options:
1. External supply. The TDM unit is intended to be supplied from a 9-15v DC supply (6-15v if the
internal battery is not fitted). The basic unit requires up to 50mA, plus any extra current drain from
the +5v output (pin 9 on the D-type). The supply can be fed in through the 2.1mm power jack
(positive to centre connector) or through pin 1 of the 9 way D connector.
2. Local +5v. The user may also power the unit by applying a regulated +5v supply to pin 9 of the Dtype. In this mode of operation the internal battery must be removed, and switch 2 set to 'on'. The
supply must be clean, and ripple free, as this mode of operation bypasses the internal supply
3. There is provision for an internal PP3 battery. This is intended as a backup power source, and for
use during experimentation and set-up. A standard, high capacity alkaline battery will provide
around 15 hours of continuous operation. (The use of rechargable batteries in this unit is not
recommended at this time)
The internal battery is enabled by the recessed slide switch on the right of the case (slide switch
backwards to enable the battery. To change the battery, the unit must be dis-assembled by removing
the polymer 'feet' and removing the four assembly screws. The battery is retained to the pcb by a
standard 'tie wrap'.
When an external supply exceeding 9v is fed to the unit (through the power jack or the D connector), the
internal battery is not used (there are steering diodes in series with both power sources)
Connecting the TDM: This unit is connected to an RS232 serial port via a standard 9 way D connector.
True (bipolar) RS232 levels are provided by this interface. The interface provides TXD/RXD, plus a
basic CTS function (indicating that the radio is busy receiving a data burst). Other pins are used for
functions specific to the TDM (mode and standby, power supplies).
Radiometrix Ltd
TDM2 RF Modem Manual
Page 2
+5V out
Frame ground
Figure 3: TDM2 DB9 Serial Port pin outs
Serial interface
The TDM2 serial interface operates at 9600 baud only, with 1 start, 8 data and 1 or 2 stop bits
Raw supply voltage input (9-15v. )
RS232 data out
RS232 data in
Pull low to disable unit. (Pin function enabled by switch 1)
Supply ground
Pull low to enter program mode. (Pin function enabled by switch 4)
No connection
Low = Unit has valid data in rx buffer
Regulated supply output. 200mA max. (independent of DTR
switching) (Pin function enabled by switch 2)
1. Pins 4 and 6 have internal pullups to +5v, pin 3 has a pulldown to 0V
2. All ' Input' pins (3,4,6) will tolerate true +/- RS232 levels. No extra buffering is required.
3. The RX_busy (CTS, pin 8) circuitry incorporates a pulse lengthening monostable, to eliminate
the strobing or 'flashing' seen with TDL2A modules during streaming data, as the buffer fills
and empties.
4. A simple addressing structure is included in the datastream. Units may be programmed onto
one of eight addresses (all units are supplied set to default addr=0)
5. A version is available in a robust extruded aluminium housing. Contact Radiometrix Sales for
Don't forget the aerial:
The TDM2 is a wireless device, and will not function without a suitable
aerial. The supplied part (a high quality 433MHz band helical type) is attached to the SMA connector
on the rear of the casing. Use sufficient (but not excessive) torque to tighten the screw collar. Fingertight is correct.
Alternative aerials may be connected to this connector via a length of RF coax. Contact technical
support for advice.
A good first demonstration can be had by:
Set up a pair of PCs, with serial (RS232) ports.
Connect them together with a null modem (pins 2/3 swap over) cable.
Run terminal emulator (ie: Hyperterminal) programs on both computers. (Port settings 9600
baud, 1+8+1, local echo)
At this point you have a simple 'teletype' link between the machines. Anything typed on one is
seen on the other.
Now replace the null modem cable with a pair of TDM2 radio modems. You will see no change.
The radio link seamlessly replaces the cable.
Radiometrix Ltd
TDM2 RF Modem Manual
Page 3
Configuring the interface: A 4 way DIP switch is located in a recess on the rear of the case.
As supplied, all switches are 'off' ('up'). These switches control certain interface functions:
SW No.
+5v/pin 9
Ext setup en
Switch 'on' to enable pin 4 switching (otherwise unit is
always on)
Switch 'on' to enable the +5v external supply pin
Switch 'on' to force unit into setup/program mode
Switch 'on' to enable pin 6 (N_PGM)
Indicators: On the front of the hosing are three LED indicators:
1) Power:
Green, on the left.
2) Transmit: Red, in the centre
3) Receive:
Red, on the right
Unit is powered when lit
When lit, the unit's transmitter is on, and it is sending a data
When lit, the unit has received a valid data packet, and is
outputting it
1) It ought to be emphasised that the TDM2 is a very simple, easy to use, device. It is also
relatively unsophisticated. The data rate is limited to 9600 baud, the link is half duplex, and
although there is a simple addressing structure, there is no provision for extensive data
buffering, FEC, or acknowledge/re-transmit error handling protocols. Inside the box, the TDM2
is simply a TDL2A radio module with necessary interface circuits, power supplies and
2) The TDM2 provides a half duplex link: Provided no two devices attempt to transmit at one time
(a 'low' on RX_busy may be used as a primitive 'CTS' indication) 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. Sync and framing words in
the packet prevent the receiver outputting garbage in the absence of signal or presence of
3) At the edge of it's range, or in the presence of other interferers, there will be packets (of 1-3
bytes each) lost, or occasionally corrupted. If a greater degree of data fidelity is needed, then the
user ought to introduce another layer of data handling. In our own tests we have used the Zmodem file transfer protocol with great success. In simpler, control type, applications these data
errors will be of lesser significance.
Radiometrix Ltd
TDM2 RF Modem Manual
Page 4
Configuring the TDM2
In order to use all the functions embedded in the on board TDL2A modem, the user must be aware of
the setup /programming facility, which allow different addresses and frequency channels to be set up,
and if necessary accesses diagnostic test modes.
As supplied, the TDM2 is set to address zero, and channel zero. To change these presets, it is necessary
to enter setup/program mode.
The TDM2 is programmed through the same RS232 port that is used for sending/receiving data. An
RS232 terminal emulator (such as Aterm or HyperTerminal) is an ideal tool.
To enter program mode either switch 3 is temporarily turned 'on', or pin 6 of the D connector is pulled
low (providing switch 4 is 'on'). In this mode the radio link is disabled, but characters sent (at 9600
baud, as normal) to the unit are echoed back on the RXD pin.
Connect the TDM2 to the PC serial port using a serial straight through cable.
The HyperTerminal should be set with the following settings.
9600 baud RS232, 8 bit data, no parity, 1 start bit, 1 or 2 stop bits. No flow control.
The unit will only respond to certain command strings:
These commands set up one of 8 unique addresses. A TDi2 will
only communicate with a unit set to the same address.
These commands select one of 5 preset channels
A TDM2 will only communicate with a another TDM2 set to the same address and the same channel.
Address and channel numbers are stored in volatile memory. On power-up the TDM2 reverts to the
default in EEPROM (as supplied this is always address 0 and Channel 0)
Writes the current set address into EEPROM as the new default.
A tilda character (~, ascii 126dec) sent by the unit indicates end of
EEPROM write sequence
Following commands are normally only used for factory diagnostics:
# <CR>
Transmit unmodulated carrier
Transmit carrier modulated with 8KHz squarewave
Transmit carrier modulated with 16KHz squarewave
Transmitter off
A Carriage Return '<CR>' (00Dhex) should be entered after each command sequence to execute it.
Releasing the 'setup' pin to high state (or turning off switch 3) returns the unit to normal operation
Radiometrix Ltd
TDM2 RF Modem Manual
Page 5
Condensed specifications
433.925MHz – CHAN0 (default channel)
433.285MHz – CHAN1
433.605MHz – CHAN2
434.245MHz – CHAN3
434.565MHz – CHAN4
Frequency stability
Channel width
Number of channels
1 of 5, user programmed
6 – 15V
30mA transmit
27mA receive/idle
(plus up to 10mA in to RS232 port)
20uA disabled
9pin D type
2.1mm connector
4 position DIP switch
Power on (green LED)
Sending (red LED)
Receiving (red LED)
94 x 107 x 33 mm (excluding connectors)
The case is an ergonomic ABS moulding, designed by HCP
A version is available in a robust extruded aluminium housing.
Contact Radiometrix Sales for details
Operating temperature
Spurious radiations
Output power
-20 °C to +70 °C (Storage -30 °C to +70 °C)
Compliant with ETSI EN 300 220-3 and EN 301 489-3
Modulation type
FM peak deviation
Adjacent channel TX power
TX spurious
10dBm (10mW) ±1dB
(A 25mW (+14dBm) power output AUS/NZ version is available)
16kbps bi-phase FSK
+/-25kHz (nominal)
spurious / adjacent channel
LO re-radiation
-105dBm for 1% BER
-80dB nominal, 75dB worst case
Baud rate
Radio channel data rate
Packet length
Flow control
Data latency
Radiometrix Ltd
9600baud (transparent, half duplex
(a 4800 baud version, TDM2-433-4 , is available to special order)
1 start, 8 data, 1 stop, no parity
16kbps peak
3 bytes
32 byte FIFO
None (‘RX busy’ pin provided)
1 of 8, user programmed
14ms (first byte into TX, to first byte out of RX)
TDM2 RF Modem Manual
Page 6
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
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:
Information Requests
Riverside House
2a Southwark Bridge Road
London SE1 9HA
Tel: +44 (0)845 456 3000 or 020 7981 3040
Fax: +44 (0)20 7783 4033
[email protected]
[email protected]
European Radiocommunications Office (ERO)
Nansensgade 19
DK 1366 Copenhagen
Tel. +45 33896300
Fax +45 33896330
[email protected]