RFM DNT90 Series Quick setup guide

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DNT90 Series
900 MHz Spread Spectrum
Wireless Transceivers
Integration Guide

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Important Regulatory Information
RFM Product FCC ID: HSW-DNT90
IC 4492A-DNT90
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 pro-
tection 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 in-
structions, may cause harmful interference to radio communications. 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:
1) Re-orientate or relocate the receiving antenna,
2) Increase the separation between the equipment and the radiator,
3) Connect the equipment to an outlet on a circuit different from that to which the receiver is connected,
4) Consult the dealer or an experienced radio/TV technician for help.
FCC Antenna Gain Restriction and MPE Statement:
The DNT90 has been designed to operate with any dipole antenna of up to 5.1 dBi of gain, any Yagi of up
to 6.1 dBi gain, or chip antenna JTI-0915AT43A0026.
The antenna(s) used for this transmitter must be installed to provide a separation distance of at least
20 cm from all persons and must not be co-located or operating in conjunction with any other antenna or
transmitter.
Industry Canada Specific Statements:
The term “IC:” before the radio certification number only signifies that Industry Canada technical specifica-
tions were met.
This Class B digital apparatus meets all requirements of the Canadian Interference Causing Equipment
Regulations. Operation is subject to the following two conditions: (1) this device may not cause harmful
interference, and (2) this device must accept any interference received, including interference that may
cause undesired operation.
Cet appareillage numérique de la classe B répond à toutes les exigences de l'interférence canadienne
causant des règlements d'équipement. L'opération est sujette aux deux conditions suivantes: (1) ce dis-
positif peut ne pas causer l'interférence nocive, et (2) ce dispositif doit accepter n'importe quelle interfé-
rence reçue, y compris l'interférence qui peut causer l'opération peu désirée.

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IC RSS-210 Detachable Antenna Gain Restriction:
This device has been designed to operate with the antennas listed below, and having a maximum gain of
6.1 dB. Antennas not included in this list or having a gain greater than 6.1 dB are strictly prohibited for
use with this device. The required antenna impedance is 50 ohms:
RFM RWA092R Omnidirectional Dipole Antenna, 2 dBi
RFM OMNI095 Omnidirectional Dipole Antenna, 5 dBi
RFM YAGI099 Directional Antenna, 6.1 dBi
Chip Antenna JTI-0915AT43A0026, -1 dBi
To reduce potential radio interference to other users, the antenna type and its gain should be so chosen
that the equivalent isotropically radiated power (e.i.r.p.) is not more than that permitted for successful
communication.
See Section 6.8 of this manual for regulatory notices and labeling requirements. Changes or modifica-
tions to a DNT90 not expressly approved by RFM may void the user’s authority to operate the module.

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Table of Contents
1.0 DNT90 Introduction .......................................................................................................................... 6
1.1 Why Spread Spectrum? ............................................................................................................ 6
1.2 Frequency Hopping versus Direct Sequence............................................................................ 7
2.0 DNT90 System Overview................................................................................................................. 8
2.1 Point-to-Point Systems .............................................................................................................. 8
2.2 Point-to-Multipoint Systems....................................................................................................... 9
2.3 Store-and-Forward Systems...................................................................................................... 9
2.4 RF Channel Access................................................................................................................. 10
2.5 DNT90 Addressing .................................................................................................................. 11
2.6 Network Linking and Slot Registration .................................................................................... 11
2.6.1 Fast Linking Techniques ................................................................................................... 12
2.7 Transparent and Protocol-formatted Serial Data..................................................................... 12
3.0 DNT90 Application Interfaces ........................................................................................................ 13
3.1 Serial Ports .............................................................................................................................. 13
3.2 SPI Port ................................................................................................................................... 13
3.3 Digital I/O ................................................................................................................................. 16
3.4 Analog I/O................................................................................................................................ 16
3.5 I/O Event Reporting and I/O Binding ....................................................................................... 17
4.0 DNT90 System Configuration ........................................................................................................ 18
4.1 Configuration Parameters........................................................................................................ 18
4.2 Configuring a Basic Point-to-Point System ............................................................................. 18
4.3 Configuring a Basic Point-to-Multipoint System ...................................................................... 18
4.4 Configuring a Customized Point-to-Point or Point-to-Multipoint System................................. 19
4.5 Configuring a Store-and-Forward System............................................................................... 20
4.6 Slot Buffer Sizes, Number of Slots, Messages per Hop and Hop Duration ............................ 21
5.0 DNT90 Application Interface Configuration.................................................................................... 23
5.1 Configuring the Serial Port ...................................................................................................... 23
5.2 Configuring the SPI Port.......................................................................................................... 24
5.3 Configuring Digital I/O ............................................................................................................. 24
5.4 Configuring Analog I/O ............................................................................................................ 24
5.5 Configuring I/O Event Reporting and I/O Binding.................................................................... 25
5.6 Configuring Sleep Mode .......................................................................................................... 26
6.0 DNT90 Hardware ........................................................................................................................... 27
6.1 Electrical Specifications........................................................................................................... 28
6.2 Module Pin Out........................................................................................................................ 29
6.3 Antenna Connector.................................................................................................................. 30
6.4 Power Supply and Input Voltages ........................................................................................... 31
6.5 ESD and Transient Protection ................................................................................................. 31
6.6 Interfacing to 5 V Logic Systems............................................................................................. 31
6.7 Mounting and Enclosures ........................................................................................................ 31
6.8 Labeling and Notices ............................................................................................................... 32
7.0 DNT90 Protocol-formatted Messages............................................................................................ 33
7.1 Protocol Formats ..................................................................................................................... 33
7.2 Message Types ....................................................................................................................... 33
7.3 Message Format Details.......................................................................................................... 34

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7.4 Configuration Parameter Registers ......................................................................................... 41
7.4.1 Bank 0x00 - Transceiver Setup......................................................................................... 41
7.4.2 Bank 0x01 - System Settings............................................................................................ 44
7.4.3 Bank 0x02 - Status Parameters ........................................................................................ 45
7.4.4 Bank 0x03 - Serial and SPI Settings................................................................................. 47
7.4.5 Bank 0x04 - Host Protocol Settings .................................................................................. 48
7.4.6 Bank 0x05 - I/O Parameters ............................................................................................. 49
7.4.7 Bank 0x06 - I/O Settings ................................................................................................... 50
7.4.8 Bank 0x0FF - Special Functions ....................................................................................... 55
7.5 Protocol-formatted Message Examples .................................................................................. 56
7.5. 1 Data Message ................................................................................................................... 56
7.5.2 Configuration Message ..................................................................................................... 57
7.5.3 Sensor Message ............................................................................................................... 57
7.5.4 Event Message ................................................................................................................. 58
8.0 DNT90DK/DNT90ADK Developer’s Kits........................................................................................ 59
8.1 Kit Contents ............................................................................................................................. 59
8.2 Additional Items Needed ......................................................................................................... 59
8.3 Developer’s Kit Default Operating Configuration..................................................................... 59
8.4 Developer’s Kit Hardware Assembly ....................................................................................... 60
8.5 DNT90 Utility Program............................................................................................................. 61
8.6 Initial Kit Operation .................................................................................................................. 62
8.6.1 Serial Communication and Radio Configuration............................................................... 65
8.7 DNT90 Interface Board Features ............................................................................................ 71
9.0 Troubleshooting ............................................................................................................................. 73
9.1 Diagnostic Port Commands..................................................................................................... 73
10.0 Appendices .................................................................................................................................... 74
10.1 Ordering Information................................................................................................................ 74
10.2 Technical Support.................................................................................................................... 74
10.3 DNT90/DNT90A Mechanical Specifications............................................................................ 75
10.4 DNT90 Development Board Schematic .................................................................................. 79
11.0 Warranty......................................................................................................................................... 82

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1.0 DNT90 Introduction
DNT90 transceivers provide highly-reliable wireless connectivity for point-to-point, point-to-multipoint and
store-and-forward radio applications. Frequency hopping spread spectrum (FHSS) technology ensures
maximum resistance to multipath fading and robustness in the presence of interfering signals, while oper-
ation in the 900 MHz ISM band allows license-free use in North America, South America and Australia.
The DNT90 supports serial data rates for host communications from 1.2 to 250 kbps, plus three SPI data
rates from 125 to 500 kbps. On-board data buffering plus an error-correcting radio protocol provide
smooth data flow and simplify the task of integration with existing applications. Key DNT90 features in-
clude:
Multipath fading resistant frequency hopping
technology with up to 52 frequency chan-
nels, 902.76 to 927.24 MHz
Receiver protected by low-loss SAW filter,
providing excellent receiver sensitivity and
interference rejection important in outdoor
applications
Ad Hoc TDMA operating mode supports a
large number of remotes with low latency
for burst data streaming
Simple interface handles both data and con-
trol at up to 250 kbps on the serial port or
500 kbps on the SPI port
Support for point-to-point, point-to-multipoint,
peer-to-peer and store & forward networks
AES encryption provides protection from
eavesdropping
FCC 15.247 and IC RSS-210 certified for
license-free operation
Nonvolatile memory stores DNT90 configura-
tion when powered off
Five mile plus range with omnidirectional
antennas (antenna height dependent)
Selectable +16 dBm (40 mW) or +22 dBm
(158 mW) transmit power levels
Transparent ARQ protocol with data
buffering ensures data integrity
Automatic I/O event reporting mode simplifies
application development
Analog and Digital I/O supports wireless
sensing applications
I/O binding mode provides wireless transmis-
sion of analog and digital values
1.1 Why Spread Spectrum?
A radio channel can be very hostile, corrupted by noise, path loss and interfering transmissions from oth-
er radios. Even in an interference-free environment, radio performance faces serious degradation from a
phenomenon known as multipath fading. Multipath fading results when two or more reflected rays of the
transmitted signal arrive at the receiving antenna with opposing phases, thereby partially or completely
canceling the signal. This problem is particularly prevalent in indoor installations. In the frequency do-
main, a multipath fade can be described as a frequency-selective notch that shifts in location and intensity
over time as reflections change due to motion of the radio or objects within its range. At any given time,
multipath fades will typically occupy 1% - 2% of the band. From a probabilistic viewpoint, a conventional
radio system faces a 1% - 2% chance of signal impairment at any given time due to multipath fading.
Spread spectrum reduces the vulnerability of a radio system to both multipath fading and jammers by dis-
tributing the transmitted signal over a larger region of the frequency band than would otherwise be neces-
sary to send the information. This allows the signal to be reconstructed even though part of it may be lost
or corrupted in transmission.

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Narrow-band versus spread spectrum transmission
Figure 1.1.1
1.2 Frequency Hopping versus Direct Sequence
The two primary approaches to spread spectrum are direct sequence spread spectrum (DSSS) and fre-
quency hopping spread spectrum (FHSS), either of which can generally be adapted to a given applica-
tion. Direct sequence spread spectrum is produced by multiplying the transmitted data stream by a much
faster, noise-like repeating pattern. The ratio by which this modulating pattern exceeds the bit rate of the
base-band data is called the processing gain, and is equal to the amount of rejection the system affords
against narrow-band interference from multipath and jammers. Transmitting the data signal as usual, but
varying the carrier frequency rapidly according to a pseudo-random pattern over a broad range of chan-
nels produces a frequency hopping spectrum system.
Forms of spread spectrum - direct sequence and frequency hopping
Figure 1.1.2

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One disadvantage of direct sequence systems is that due to design issues related to broadband transmit-
ters and receivers, they generally employ only a minimal amount of spreading, often no more than the
minimum required by the regulating agencies. For this reason, the ability of DSSS systems to overcome
fading and in-band jammers is relatively weak. By contrast, FHSS systems are capable of hopping
throughout the entire band, statistically reducing the chances that a transmission will be affected by fad-
ing or interference. This means that a FHSS system will degrade gracefully as the band gets noisier,
while a DSSS system may exhibit uneven coverage or work well until a certain point and then give out
completely.
Because it offers greater immunity to interfering signals, FHSS is often the preferred choice for co-located
systems. Since direct sequence signals are very wide, they can offer only a few non-overlapping chan-
nels, whereas multiple hoppers can interleave, minimizing interference. Frequency hopping systems do
carry some disadvantages, in that they require an initial acquisition period during which the receiver must
lock on to the moving carrier of the transmitter before any data can be sent, which typically takes several
seconds. In summary, frequency hopping systems generally feature greater coverage and channel utiliza-
tion than comparable direct sequence systems. Of course, other implementation factors such as size,
cost, power consumption and ease of implementation must also be considered before a final radio design
choice can be made.
2.0 DNT90 System Overview
A DNT90 radio can be configured to operate in one of three modes - base, remote or router. A base con-
trols a DNT90 system, and interfaces to an application host such as a PC or Internet gateway. A remote
functions to transmit or receive serial, digital (state) and analog data. A router alternates between func-
tioning as a remote on one hop and a network base on the next hop. When acting as a remote, the router
stores messages it receives from its parent, and then repeats the messages to its child radios when act-
ing as a network base. Likewise, a router will store messages received from its child radios when acting
as a base, and repeat them to its parent when acting as a remote. Any message addressed directly to a
router is processed by the router rather than being repeated.
2.1 Point-to-Point Systems
A DNT90 system contains at least one network. The simplest DNT90 topology is a point-to-point system,
as shown in Figure 2.1.1. This system consists of a base and one remote forming a single network. Point-
to-point systems are often used to replace wired serial connections. Point-to-point systems are also used
to transmit switch positions or analog signals from one location to another.
Figure 2.1.1

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2.2 Point-to-Multipoint Systems
Figure 2.2.1 shows the topology of a point-to-multipoint (star) system, which consists of a base and more
than one remote in a single network. Point-to-multipoint systems are typically used for data, sensor and
alarm systems. While most traffic in a point-to-multipoint system is between the base and the remotes,
DNT90 technology also allows for peer-to-peer communication from one remote to another.
Figure 2.2.1
2.3 Store-and-Forward Systems
Figure 2.3.1 shows the topology of a store-and-forward system, which consists of a base, one or more
routers, one or more remotes, and two or more networks. Networks in a store-and-forward system form
around the base and each router. The base and the routers are referred to as the parents of the networks
they form. The rest of the radios in each network are referred to as child radios. Note that a router is a
child of the base or another router while being the parent of its own network. Each network parent trans-
mits beacons to allow child radios to synchronize with its hopping pattern and join its network. Different
frequency hopping patterns are used by the parent radios in a system, minimizing interference between
networks.
Store-and-forward systems are used to cover larger areas than is possible with point-to-point or point to-
multipoint systems. The trade-off in store-and-forward systems is longer delivery times due to receiving
and retransmitting a message several times. Store-and-forward systems are especially useful in applica-
tions such as agriculture where data is only collected periodically.

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Figure 2.3.1
2.4 RF Channel Access
The time a DNT90 network stays on each frequency in its hopping pattern is called the hop duration or
dwell time, which can be configured from 8 to 100 ms. Radio communication during each dwell is orga-
nized as a time division multiple access (TDMA) frame. A DNT90 frame begins with a base-mode beacon,
followed by 1 to 8 time slots used by the network children to transmit to their parent, as shown in Figure
2.4.1. A base-mode beacon can include up to 8 messages addressed to one or more child radios. The
number of slots is chosen accommodate the number of children that need to send messages each hop.
S y s t e m / N e t w o r k
C o n t r o l
M e s s a g e s t o
N e t w o r k C h i l d r e n
B a s e - M o d e
B e a c o n
E x a m p l e D N T 0 C o m m u n i c a t i o n F r a m e
A s s i g n e d
S l o t
O p e n
S l o t
O p e n
S l o t
M e s s a g e s
f r o m C h i l d
Figure 2.4.1
Each beacon includes the status of all slots - either registered (assigned) or open. When a child radio has
information to transmit to its parent, it randomly selects one of the open slots and transmits all or the first
part of its data. If the parent successfully receives the transmission, it includes the child’s MAC address in
the next beacon. This signals the child radio that the slot is temporarily registered to it, allowing the child
to efficiently stream any remaining data to the base hop-by-hop until it is all sent.
If a child radio does not see its address in the next beacon following its transmission, it again randomly
selects an open slot and retransmits its data. During times when there are no open slots, a child radio