Radiometrix Ltd.

UHF FM Radio Packet Modem

page 4

2 The Host Interface

The connection to the RPM3 is a full duplex serial interface supporting baud rates from 600bps to

115200bps. Additional control signals are provided to assist in flow control, configuration and power

saving in the RPM3.

Figure 5: Physical dimensions and pinouts

Pin name

Pin

Pin Function

In/Out

Description

RF GND

1, 3

RF signal ground

BNC casing/coax braid connection

RF

2

RF signal

Input or

Output

Antenna pin/coax core connection

RXSELCT

4

Receiver Select

Input

or Output

Internal RF Receiver Enable to BiM3A

or RF Receiver Active Indicator

TX SELECT

5

Transmitter Select

Input

or Output

Internal RF Transmitter Enable to BiM3A

or RF Transmitter Active Indicator

TXD/AF

7

Transmitted Data

or demodulated signal

Input

or Output

Transmitted Packetised Data to BiM3A

Analogue Demodulated signal from BiM3A

D3

8

FRPC Data line

NC

Internal data line between RPM and FRPC

D2

9

FRPC Data line

NC

Internal data line between RPM and FRPC

SIGNAL

10

Preamble Detect

Output

Valid preamble indicator

RST

11

FRPC reset

NC

Resets FRPC which also isolates BiM3A

RXA

12

Receive Acknowledge

NC

RPM to FRPC download Request Acknowledge

RXR

13

Receive Request

Output

Valid Data packet indicator

RESET

14

Reset

Input

Hardware reset of the RPM3

SETUP

15

Enter Setup

Input

Enter RPM3 configurator after a RESET

WAKE/DTR

16

Wake or Shutdown

Input

Wakes RPM3 when low, shuts down when high

TXD

17

Serial transmitted data

Input

Host (DTE) to RPM3 serial transmit data

RXD

18

Serial Received data

Output

RPM3 to host (DTE) serial received data

CTS

19

Clear To Send

Output

Hardware flow control of data from host (DTE)

DEFAULT

20

Force 9600bps

Input

Force the RPM3 serial interface to 9600bps

VCC

21

Vcc Supply

Input

+5VDC or +3VDC regulated supply

GND

6, 22

Ground

-

Supply Ground internally connected to GND

Notes: 1. RXD/TXD lines are true data

3. Logic levels are 5V CMOS unless 3V variant is used.

4. WAKE pin should be pulled to ground if DTE cannot provide DTR signal

The Reset signal is internally pulled up to Vcc via a 10k

Ω resistor. A reset aborts any transfers in

progress and restarts the RPM3.

Minimum low time: 1.0

µs, after reset is released (returned high). The host should allow a delay

1ms after reset for the RPM3 to initialise itself.