Radiometrix Ltd

KRX2

page 3

Pin description

Pin

Name

Function

1

RSSI

Analogue output of received signal strength indication with 60dB range.

See page 5 for typical characteristics.

2

RESERVED Do not connect anything to this pin

3

0V

DC supply 0V. Internally connected to pins 4 & 9 and module screen.

4

0V

DC supply 0V. Internally connected to pins 3 & 9 and module screen.

5

LRN (OUT)

Digital indication of Learn function - see below for operational description.

6

RXD

Digital output from the internal data slicer, i.e. a squared version of the

signal on pin 7 (AF). It may be used to drive external decoders.

7

AF

Buffered and filtered analogue output from the FM demodulator. Standing

DC bias 2V approx. External load should be >10k

Ω // <100pF.

8

+5V

+5V regulated power supply (4.5 - 5.25V)

9

RF GND

RF ground pin, internally connected to the module screen and pins 3 & 4

(0V). This pin should be connected to the RF return path (coax braid, main

PCB ground plane etc.)

10

RF IN

50

Ω input from the antenna, DC isolated.

11

MODE

Digital input, normally high – high=10ms monostable output,

low=momentary – see below for futher description.

12

LRN (IN)

Digital input, normally high – taken low for learning transmitters or

clearing decoder NV memory – see below for detailed description.

13

/RST

Resets Decoder when taken low. NV memory and receiver are unaffected.

14

RESERVED Do not connect anything to this pin.

15

RESERVED Do not connect anything to this pin.

16

LOW BATT

Digital output – indicates that the supply voltage at the transmitter of the

current message has fallen below approx. 3.8V.

17

S3

Digital output – function code of the current message

18

S2

Digital output – function code of the current message

19

S1

Digital output – function code of the current message

20

S0

Digital output – function code of the current message

Using KRX2

A simple connection diagram for experimental purposes is shown in Figure 3.

The Mode switch is connected between MODE and 0V and the Learn button is connected between LRN

(IN) and 0V. The antenna can be just a few centimetres of wire, for test purposes. Refer to antenna

requirements at the end of this datasheet for operational recommendations. The 5V shown would

normally be supplied by a regulated low-noise PSU. Remaining digital outputs are all connected to

LEDs to show the operation of the module.

CAUTION!

Take care that the supply never exceeds 5.5V, even momentarily: if this happens the module may be

permanently damaged.

Learning a transmitter

The Learn button is pressed momentarily (<1s) and a 5-second (approx.) window follows, during which

Learn LED “L” is lit and a message received from a Radiometrix code-hopped transmitter during this

period is used to Learn that transmitter into the KRX2 memory. The function code used to activate the

transmitter during learning is also stored in memory and when the same function code is used again

from that transmitter during normal operation the Learn LED lights to indicate this. Note: if a

transmitter has already been stored it is simply re-learned (with the function code updated if this is

different). Upon learning a transmitter the Learn LED flashes several times to indicate success.