Radiometrix Ltd

CXT/CXR – Multi channel Remote Controller Data Sheet

page 2

Easy control functions with CXT and CXR:

There are certain user applications where a very simple ‘on/off’ control function is needed (for example:

control of floodlights, alarm sounders, machine override shutdown). Normally such applications require a

simple microprocessor or dedicated remote control chip to be added to the radio module, incurring extra size,

cost and sometimes software overhead.

Not anymore. The CXT and CXR module pair (based on either LMT2/LMR2 (UHF version) or LMT1/LMR1

(VHF version)) includes a simple-to-use single function controller/actuator, implemented in the firmware of

the radio’s internal processor. This code allows the unit to be used as a very simple remote control product,

with either a latched or a momentary output. No external control device is required.

Two inputs are provided on the CXT transmitter. Grounding input A sends a coded datastream to the CXR

receiver which commands it to latch it’s A output high (+3v). Grounding the transmitter B input sends a

datastream which resets the receiver A pin to zero. Also, for the duration of the B transmission, the receiver

B output is high. The minimum duration of a B output pulse is 300mS.

The CXT transmits whenever either A or B are low, but to function the TXE must also be low (this can be tied

low for simplicity, or diode 'or'ed with the A, B inputs to minimise current consumption)

The data format uses is a modified biphase format with an average data rate of 600 bits per second. A 42 bit

data burst is used (preceded by ample preamble). This incorporates a 16 bit unit address. This is easily

modified via the 2400 baud serial communication port (SI pin), which allows both the unit address and the

channel number (1 of 32 operating frequencies) to be easily modified. Commands are in an easy to

understand ‘ascii text and decimal numbers’ form, simply entered by hand from any terminal program. Once

programmed, values are stored in non-volatile memory.