RFD900x Data Sheet V1.1
www.rfdesign.com.au
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RFD900x Radio Modem User Manual
902-928MHz frequency band
RFD900x User Manual V2.0
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General Cautions
During operation there must be a separation distance of 20cm between all persons and the antenna.
Ensure that all used RF connectors are secure and properly terminated.
When used in the US - FCC Caution
Caution: The user is cautioned that changes or modifications not expressly approved by the party responsible
for compliance could void the user's authority to operate the equipment.
Note: This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant
to part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful
interference in a residential installation. This equipment generates, uses and can radiate radio frequency
energy and, if not installed and used in accordance with the instructions, may cause harmful interference to
radio communications. However, there is no guarantee that interference will not occur in a particular
installation. If this equipment does cause harmful interference to radio or television reception, which can be
determined by turning
the equipment off and on, the user is encouraged to try to correct the interference by one or more of the
following measures:
—Reorient or relocate the receiving antenna.
—Increase the separation between the equipment and receiver.
—Connect the equipment into an outlet on a circuit different from that to which the receiver is connected.
—Consult the dealer or an experienced radio/TV technician for help.
This equipment complies with FCC’s RF radiation exposure limits set forth for an uncontrolled environment.
The antenna(s) used for this transmitter must be installed and operated to provide a separation distance of at
least 20 cm from all persons and must not be collocated or operating in conjunction with any other antenna or
transmitter. Installers must ensure that 20cm separation distance will be maintained between the device
(excluding its handset) and users.
When used in Canada - ISED Caution
This device complies with RSS 210 of the Industry Canada Rules. Operation is subject to the following two
conditions:
(1) this device may not cause interference, and (2) this device must accept any interference, including
interference that may cause undesired operation of the device.
Le présent appareil est conforme aux CNR d’Industrie Canada applicables aux appareils radio exempts de
licence. L’exploitation est autorisée aux deux conditions suivantes :
(1) l’appareil ne doit pas produire de brouillage, et (2) l’utilisateur de l’appareil doit accepter tout brouillage
radioélectrique subi, même si le brouillage est susceptible d’en compromettre le fonctionnement.
This equipment complies with Canada radiation exposure limits set forth for uncontrolled environments. This
equipment should be installed and operated with a minimum distance of 20cm （may be adjusted according
to actual calculation result） between the radiator and your body.
This transmitter must not be co-located or operating in conjunction with any other antenna or transmitter.
Déclaration d’IC sur l’exposition aux radiations:
Cet équipement est conforme aux limites d’exposition aux radiations définies par le Canada pour des
environnements non contrôlés. Cet équipement doit être installé et utilisé à une distance minimum de 20 cm
entre l’antenne et votre corps.
Cet émetteur ne doit pas être installé au même endroit ni utilisé avec une autre antenne ou un autre émetteur
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Acceptable Antennas
This device has been designed to operate with the antenna(s) listed below and having a maximum gain of 3 dBi.
Antennas not included in this list or having a gain greater than 3 dBi are strictly prohibited for use with this device.
The required antenna impedance is 50 ohms.
Acceptable antenna – 3dBi RFD whip.
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Table of contents
1 Key Features .................................................................................................................................... 5
2 Specifications .................................................................................................................................. 6
3 OEM Labelling ................................................................................................................................. 7
4 Pin signals and layout ...................................................................................................................... 8
5 Physical dimensions ........................................................................................................................ 9
6 Software/GCS Support .................................................................................................................. 10
7 Diversity ........................................................................................................................................ 11
7.1 Spatial diversity ..................................................................................................................... 11
7.2 Polarisation diversity ............................................................................................................. 11
8 Network options ........................................................................................................................... 12
8.1 Simple pair (P2P) ................................................................................................................... 12
8.2 Asynchronous non-hopping mesh ........................................................................................ 12
8.3 Multipoint synchronised mesh ............................................................................................. 13
9 Frequently asked questions (FAQ) ................................................................................................ 14
9.1 How many antennas do I need to use? ................................................................................. 14
9.2 How do I connect the FTDI cable to the modem? ................................................................ 14
9.3 What do I need to upload the firmware or to change the modem configuration? .............. 14
9.4 I upgraded to asynchronous firmware and the modems don't connect anymore? ............. 14
9.5 How do I configure 2 base stations and one Airborne platform with 3 modems?
(Asynchronous) ................................................................................................................................. 14
10 Useful links ................................................................................................................................ 16
11 Revision History ......................................................................................................................... 16
RFD900x User Manual V2.0
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1 Key Features
Features
• Out of the box RF communications.
• Air data rate speeds of up to 224kbps
• Diversity antenna support
• Weight of 14g
• Outdoor RF line-of-site range of 40km or
more depending on antenna
configuration
Operational
• Operating voltage: 5V, I/O Voltage (3.3V)
• Temperature range: -40°C to +85°C
• Dimensions of 30mm x 57.7mm x 12.8mm
• Current consumption:
TX mode: ~1A peak at +30dBm,
RX mode: 60mA (typical)
Applications
• Telemetry data
• UAV control
• Remote weather station
• House automation
• Long range RC
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2 Specifications
Performance
Supported RF Data Rates
12 to 224 kbps dependent on type and version of firmware
Indoor Range
500m – 1km
Line-Of-Sight Range
40km or more depending on antennas and settings
Transmit Power
0 to 30dBm in 1dBm steps
Receiver Sensitivity
>121dBm at low data rates
Low Noise Amplifier
>20dB gain
Features
Serial Data Interface
+3.3V nominal, 3.3V tolerant
Configuration Method
AT Commands, APM Planner, RF Design Modem Tools
Frequency Band
902MHz - 928MHz
Interference Immunity
FHSS (Frequency Hopping Spread Spectrum)
Serial Interface Data Rate
2400 to 1000000 bps dependent on type and version of
firmware
Antenna Connection
2 x RPSMA diversity switched ports
GPIO
6 pins (Digital, PPM capable)
Compliance Standards
FCC Part 15.247, AS/NZS 4268:2012
Networking and Security
Addressing Options
Network ID: 0 –255
Channels
Up to 51 Frequency Hopping Channels
Supported Network Topologies
Point-to-point and asynchronous mesh1 and multipoint
synchronous mesh
1
1
Only available in separate firmware versions available on the RFD website
Power Requirements
Supply Voltage
+5V nominal (+5V min, +5.5V Max, +6V ABS Max),
Transmit Current
~1A peak at max power
Receive Current
~60mA
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3 OEM Labelling
For equipment containing the RFD-900x where the RFD-900x label is not visible the following applies.
Equipment using the RFD 900x in the USA must display a label referring to the enclosed module. This
label must contain the words “Contains FCC ID: 2ADLE-900X”.
Equipment using the RFD 900x in Canada must display a label referring to the enclosed module. This
label must contain the words “Contains IC ID: 24610-900X”.
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4 Pin signals and layout
Pin #
Name
Direction
Description
Max Voltage
1
GND
-
Ground
0V 2 GND
-
Ground
0V 3 CTS
Either
Clear to send
3.3V
4
Vcc - Power supply
5V 5 Vusb
-
Power supply from USB
5V 6 Vusb
-
Power supply from USB
5V 7 RX
Input
UART Data In
3.3V
8
GPIO5/P3.4
Either
Digital I/O
3.3V
9
TX
Output
UART Data Out
3.3V
10
GPIO4/P3.3
Either
Digital I/O
3.3V
11
RTS
Either
Request to send
3.3V
12
GPIO3/P1.3
Either
Digital I/O
3.3V
13
GPIO0/P1.0
Either
Digital I/O
3.3V
14
GPIO2/P1.2
Either
Digital I/O
3.3V
15
GPIO1/P1.1
Either
Digital I/O, PPM I/O
3.3V
16
GND
-
Ground
0V
Figure 5-1: Physical pin layout of the RFD900x Radio Modem
GPIO pins will configure for 40kOhm pull down or pull up based on setting as input or output. They
can sink or source approximately 5 mA each.
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5 Physical dimensions
RFD900x User Manual V2.0
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6 Software/GCS Support
The default firmware (see “Useful Links”) is a development of the open source project called “SiK” and
was created by Mike Smith. It has been further developed and modified by Andrew Tridgell and
RFDesign.
The modems feature a boot loader to facilitate field upgrade of the modem firmware via the serial
port. This is most easily performed by using the latest version RFD Modem tools (see “Useful links”)
Parameters such as power levels, air data rates, serial speeds, GPIO pins etc can all be custom set by
the user using the AT Command set, the RFD Modem Tools V2 or later and APM Planner.
Default serial port settings are as follows:
• 57600 baud
• No parity
• 8 data bits
• 1 stop bit
The RFD900x Radio Modem has many software features including:
• Frequency Hopping Spread Spectrum
• Transparent Serial Link
• Configuration by AT commands for local radio, RT Commands for remote radio
• User configurable serial data rates and air data rates
• Error correction routines
• 128-bit AES hardware encryption with user settable key
• MAVLink protocol framing (user selectable)
• MAVLink radio status reporting (Local RSSI, Remote RSSI, Local Noise, Remote Noise)
• Automatic antenna diversity switching on a packet basis in real-time
• Automatic duty cycle throttling based on radio temperature to avoid overheating
• PPM (R/C signal) pass through (Control vehicle across radio).
• GIPO pin mirroring
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7 Diversity
The RFD900x has two antenna ports and firmware which supports diversity operation of antennas.
During the receive sequence the modem will check both antennas and select the antenna with the
best receive signal. The antenna selected during receive is then also used for subsequent transmission.
In the case of only one antenna connected, it will automatically select the port with the antenna
connected. Testing by Silicon Labs has shown that link budgets can be improved up to the order of
8dB by employing a diversity scheme.
7.1 Spatial diversity
Spatial diversity is the case where the antennas are separated by some distance from one another. It
is recommended that two antennas connected to the RDF900 modem be separated by at least 25cm,
more if possible.
7.2 Polarisation diversity
Polarisation diversity is the case where the antennas are perpendicular to each other. i.e. one vertical,
and one horizontal. This is effective in reducing multipath effects which affect one or the other
polarisation. This scheme also helps to maintain the link between non-static objects such as aircraft
performing acrobatics by increasing the likelihood that one antenna will maintain the same
polarisation as an antenna on the other side of the link. Figure 8-1 depicts how two right-angle
monopole antennas can be positioned to achieve polarisation diversity.
Figure 8-1: Antenna configuration to achieve polarisation diversity
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8 Network options
RFD900x support firmware for simple pair (peer to peer), asynchronous mesh network and multipoint
network. Available for download from the website (see “Useful Links”).
8.1 Simple pair (P2P)
The out-of-the-box firmware of the RFD900x radio modem is set to work in simple pair mode. If you
purchased a bundle, you are only required to connect the antennas and supply to initiate the link. As
soon as the pair synchronises, the on-board LED will become solid green.
Figure 8-1 Peer to peer modem pair network
8.2 Asynchronous non-hopping mesh
The asynchronous non-forwarding mesh firmware offers a straight forward communication option that
allows the user to quickly transmit and receive data across a great distance between two or more
nodes. Figure 9-2 depicts this communication topology. If all the nodes are within range and have
compatible parameters, communication between them will succeed.
Node 1
Node 2
Nodes within range
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Figure 8-2 Asynchronous mesh topology
It is also possible to establish forwarding between nodes in the network. (See the asynchronous
firmware datasheet for details)
8.3 Multipoint synchronised mesh
The network requires that one of the devices assumes a base role to control the timeslot distribution
of the surrounding radios. If one the nodes is out of the base’s range, communication is still possible
if the parameter SyncAny is properly set.
Figure 8-3 Multipoint mesh topology
Node 1
Node 2
Node 3
Node 0
Node 4
All nodes within range
Node 1
Node 2
Node 3
Node 0
Base
Within base node range
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9 Frequently asked questions (FAQ)
9.1 How many antennas do I need to use?
One is the minimum. Two is recommended.
9.2 How do I connect the FTDI cable to the modem?
The black cable of the FTDI (pin 1) should connect to pin 1 on the modem as shown in Figure 10-1.
Figure 10-1: An FTDI cable connected to the RFD900x modem
9.3 What do I need to upload the firmware or to change the modem
configuration?
Download the latest firmware (see “Useful Links”). Download the RFD900x Modem Tools (see “Useful
Links”). Connect the FTDI cable to the modem and to a computer. Use the RFD900x Modem Tools to
upload the latest firmware or to change the modem configuration (see “RFD900x Modem Tools User
Manual”).
9.4 I upgraded to asynchronous firmware and the modems don't connect
anymore?
The default setting for a modem is to have a NODEID set to 1 and DESTID set to 2. As communication
is addressed NODEID must be different for all units and DESTID will set the modems to connect to.
9.5 How do I configure 2 base stations and one Airborne platform with 3
modems? (Asynchronous)
Set the Airborne platform as follows:
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NODEID = 1
DESTID = 65535, (32768 from version 2.45F)
MAVLINK = 1
Set the ground station as follows:
NODEID = 2 or 3
DESTID = 1
MAVLINK = 1
This will allow the airborne modem to handover to multiple ground stations as it flies from the
coverage area of one ground station, to another. Both ground stations can be connected and can
control the Airborne platform simultaneously. (APM Planner using MAVLink)
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10 Useful links
RFD900x Firmware
http://rfdesign.com.au/firmware/
RFD SiK firmware is default
RFD Asynchronous firmware
RFD Multipoint firmware
RFD900x Flash Programmer
http://rfdesign.com.au/downloads/
FTDI Cable documentation
http://www.ftdichip.com/Support/Documents/DataSheets/Cables/DS_TTL-232R_CABLES.pdf
11 Revision History
Version
Date
Changes
1.0
22/09/17
Release document
1.1
2.0
2.1
22/05/18
1/11/18
8/1/2019
Updated to correct typos, mistakes and changes in new versions
Updated for Compliance
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