Radiometrix Ltd

CPX2 Data Sheet

page 4

Pin description

Pin

Name

Function

1

GND

Ground

2

RXD

Received Data output at 3V UART (inverted RS232) level

3

TXD

Transmit Data input at 3V UART (inverted RS232) level [No pull-up]

4

/TXON

/RXOFF

/TXON Active low Transmitter ON indicator Output [Transmit Mode]

/RXOFF Active low Receiver hot Standby Input [Receive Mode]

Open drain, 50k

 internal pull-up

5

VDD

3.3V DC (externally regulated power supply)

RSSI

Received Signal Strength Indicator output

(An optional pad for wire connection)

1a

RF

RF in/out (50

 impedance)

2a

RFGND

RF Ground

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