RFD21733 Datasheet, PDF (33/76 Pages) List of Unclassifed Manufacturers – Compliance Approved 2.4 GHz RF Transceiver Modules with Built-In RFDP8 Application Protocol

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7/10/2011 1:40 AM
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RFD21733 • FCC • IC
RFD21743 • FCC
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RFDP8
RF Module
RFD21733
RFD21735
RFD21737
RFD21738
RFD21739
RFDP8
RFDANT
RFD21742
RFD21743
RFD21772
RFD21773
KEYFOBs
Mode 3 – 9600 baud UART - Serial Transceiver (Network)
RFDANTModule Pin Label
Pin # Pin #
2
13 +V
1
10 GND
5
16 Mode Select 0
6
17 Mode Select 1
7
3 Mode Select 2
8
4 Learn / Status
9
5 Logic IO
10
6 RXD
11
7 TXD
Direction Function
Input
Input
Input
Input
Input
I/O
I/O
Output
Input
+V Power
Ground
Tie to +V
Tie to +V
Tie to GND
Pulse high through a 220 ohm series resistor to enter learn
mode. LED Learn Status Output. Must be pulled to ground
through a 47k resistor and must have series a resistor.
Bidirectional switch logic I/O, if not used then must be pulled to
ground through a 47k resistor. Also, must have a series
resistor.
RX Data Out, UART output of received data. 9600-8N1
TX Data In, UART input of data to transmit. 9600-8N1
IMPORTANT NOTE:
The RXD pin is DATA OUTPUT. The data that the radio receives will come out of this pin.
The TXD pin is DATA INPUT. Drive this pin with the data that you want the radio to send.
This applies to both UART modes, Mode 2 and Mode 3.
There are two conventions in industry when referring to TXD and RXD pins. The TXD stands for Transmit Data
and the RXD stands for Receive Data. The conventions conflict when it comes to determining from which
prospective are the labels referenced. For example, TXD in modes industry devices indicates data being
transmitted out from that pin, indicating that pin is an output. The same goes for RXD, meaning data being
transmitted into that pin from an outside device, indicating that pin is an input. That is correct for most non-
communication devices in industry. HOWEVER, this device, when functioning in its UART mode, functions as a
communications device, “A Wireless Pipe”, therefore the pin functions are reversed since they are from the
radios prospective which is used in the RF communications field. In the RF communications field TXD means
data to be transmitted, indicating the TXD pin is an input. The same goes for RXD from the radio prospective,
which indicates that pin is an output, which is responsible for outputting the data the radio has received. Both
references are right, its just a matter of knowing which one to use. If you are ever in doubt, about the direction of
data signals, it is always recommended to place a 1k series resistor on the TXD pin and RXD pins, in between the
radio and your device so there is never any chance of a possible conflict while you are prototyping causing device
damage.
Mode 2 and Mode 3 are both 9600 baud, half-duplex UART modes, suitable for connection to a microcontroller, or
a level translator (such as a MAX202), then to an RS-232 port. RF transmission takes priority over RF reception,
so that a module will not receive anything over the air if it is given a full-speed stream of serial data on its TXD
input pin. Only when you stop sending data, there will be a chance for you to receive data.
The UART is configured for 9600 baud, 8 data bits, 1 stop bit, and no parity. Because the module does not
perform any parity checking on the data stream, it is possible to use 7 data bits with even or odd parity instead of
8 data bits with no parity.
When in UART mode, the radio device remains in an active state with the radio enabled in receive mode.
If you are only using the module as a receiver, you must terminate the TXD line with about a 47k pull up resistor
to +V so you do not leave a floating input which may cause unintentional transmissions by the module detecting
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