RFD21792 View Datasheet(PDF) - Unspecified

Part Name

Description

Manufacturer

RFD21792

Compliance Approved 2.4 GHz RF Transceiver Modules with Built-In RFDP8 Application Protocol

Unspecified 

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7/10/2011 1:40 AM

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RFDP8

RF Module

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KEYFOBs

Byte Bit 7

1

2

3

4

5

Bit 6

Input 3

Bit 5

Input 2

Bit 4 Bit 3

Input 1/

RFID

ESN Byte 1

ESN Byte 2

ESN Byte 3

ESN Byte 4

Bit 2

Bit 1

Bit 0

RFID

In the first byte, bits 6 through 4 carry the state of the logic inputs, with a ‘1’ indicating the logic input on the

transmitter is high, and a ‘0’ indicating it is low. An RFID Transmitter will set both bits 0 and 4 to indicate that it is

a periodic transmission from an RFID Transmitter, and is set to ‘1’ if this is the case.

For example, if an RFID Transmitter with ESN 314CE686 sent a packet on its 2-second interval, a UART would

receive the bytes 11 31 4C E6 86 in binary format.

If input #1 on that same RFID transmitter were pulled high, the UART would receive the bytes 10 31 4C E6 86 in

binary format; since bit 0 is clear, the receiver can tell that this was not a periodic transmission.

Most ESN’s will contain at least one unprintable character, and so this data will not be suitable for displaying

directly in a terminal package (such as HyperTerminal), but a PC-based program or an embedded system (such

as the BASIC Stamp) can collect the data and display it in a more friendly fashion.

There is a very useful tool on the web called RealTerm, it is a HyperTerminal like software which can be put into

binary-mode and with it you can easily view the individual bytes sent from a serial transmitter to a UART receiver.

The ESN which the UART receives is the same one that is in the packet header. If the UART is in Network Mode,

and has not learned the ESN, it will never receive the packet, and there will be no output on the serial port.

Serial UART to Logic Receiver

A UART can also send data to a logic receiver, which will decode the data and assert its outputs as though it

received a packet from a logic transmitter. The data format is very similar to the one described in the previous

section. The differences matter only when the receiver is in Network Mode.

The UART must follow a packet with at least 15ms of no data so that all bytes as described below are sent as a

single packet.

Note that a UART can send a single zero byte – all bits clear – to force a receiver to turn off its outputs

immediately, regardless of hang time.

Format 1:

Byte Bit 7

1

Bit 6 Bit 5 Bit 4

Output 3 Output 2 Output 1

Bit 3

Bit 2

Bit 1

Bit 0

When the receiver is not in Network Mode, the receiver will accept any packet it receives, and so this is the

preferred format.

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