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

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keeps its data queued and continues to look for an open slot in each beacon until at least one slot be-
comes available. The access method the DNT90 uses is referred to as Ad Hoc TDMA.
2.5 DNT90 Addressing
Each DNT90 has a unique MAC address. The MAC address can be read or bar-code scanned from the
label on top of each radio. A DNT90 radio in any mode (base/router/remote) can be addressed using its
MAC address. A DNT90 base can be addressed using either its MAC address or address 0x000000. A
DNT90 can send a message to all other DNT90’s in its system by using the broadcast address
0xFFFFFF.
The base and all routers (parents) hold base-mode network IDs, which are transmitted in every beacon.
All routers and remotes hold parent network IDs and optionally alternate parent network IDs to compare
against the base-mode network IDs in the beacons they receive. A child router or remote is allowed to
join a parent if its parent network ID or alternate parent network ID matches the parent’s base-mode net-
work ID, or with any parent when its parent network ID is set to 0xFF (wildcard).
In a point-to-point or point-to-multipoint system, the default base-mode network ID of 0xFF (wildcard) can
be used. In a store-and-forward system, however, the base-mode network IDs of all routers must be set
to different values between 0x00 to 0x3F. If the base-mode network ID of 0x00 is assigned to a router, the
base must be assigned an unused base-mode network ID between 0x01 and 0x3F. Leaving all parent
network IDs in a store-and-forward system set to the default value of 0xFF allows networks to automati-
cally form, and self-repair if a parent router fails. Enabling the alternate parent network ID also provides
self-repairing message routing.
All DNT90 radios hold a system ID that can be used to distinguish systems that physically overlap. In a
DNT90 system, the system ID must be different from those used by overlapping systems to provide mes-
sage filtering. Also, using different base-mode network IDs for all networks in overlapping systems helps
reduce hopping pattern collisions.
The store-and-forward path between the base and any other radio in a system can be determined by
reading the radio’s ParentMacAddress parameter. If this address is not the base, then reading the
ParentMacAddress parameter of its parent, grandparent, etc., in succession reveals the complete path to
the base. Path determination is useful in optimizing and troubleshooting systems during commissioning
and maintenance.
2.6 Network Linking and Slot Registration
When first turned on, a DNT90 router or remote rapidly scans all frequency channels in its operating band
to acquire synchronization and link to a parent based on a system ID match plus a base-mode network ID
to parent network ID/alternate parent network ID match (or by using a wildcard (0xFF) parent network ID).
In addition to the slot status and the MAC addresses of child radios holding slot registrations, each base-
mode beacon includes one of a number of cycled control parameters. The cycled parameters are collect-
ed by child radios, allowing them to register with a parent, and to later follow any control parameter
changes. When a router or remote has collected a full set of cycled parameters, it can issue an optional
initial heartbeat message and then optional periodic heartbeat messages which allow an application to
maintain the status of all routers and remotes in its DNT90 system.

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When a router/remote has data to send to its parent, it picks an open slot at random and transmits. It then
looks for its MAC address in the next beacon. If its MAC address is present in the beacon, it is temporarily
registered to the slot and continues to use it until all current data is sent, or its MAC address drops off the
beacon.
2.6.1 Fast Linking Techniques
Minimizing linking time is important in certain applications. For example, when the remotes in a system
are battery powered and wake from sleep occasionally to report data. Minimizing linking time increases
the operating battery life of the remotes. The basic techniques to reduce linking time include:
- use no more hop duration (dwell time) than necessary
- use no more slots than necessary for the application
- use no larger base slot size (BSS) than necessary
- transmit only dynamic cycle parameters once system nodes have static parameters
Once a complete set of cycled parameters has been receive by all routers and remotes in a system and
stored in memory, it is not necessary to send all of them again during a re-linking, as long as the system
configuration remains stable.
As discussed in Section 7.4.1, the base station in a DNT90 system can be configured to transmit “fast
beacons” for a period of time when powered up, reset or triggered with the FastBeaconTrig parameter.
Fast beacons are sent using a very short hop dwell time, facilitating fast system linking.
2.7 Transparent and Protocol-formatted Serial Data
A DNT90 remote can directly input and output data bytes and data strings on its serial port. This is re-
ferred to as transparent serial port operation. In a point-to-point system, the base can also be configured
for transparent serial port operation.
In all other cases, serial data must be protocol formatted:
- configuration commands and replies
- I/O event messages
- announcement messages including heartbeats
Protocol-formatted messages are discussed in detail in Section 7. Briefly, protocol-formatted messages
include a start-of-messages character, message length and message type information, the destination
address of the message, and the message payload.
Transparent data is routed using a remote transparent destination address. In a remote, this address de-
faults to the base, 0x000000, and in the base this address defaults to broadcast, 0xFFFFFF. These de-
faults can be overridden with specific radio addresses. For example, it is possible to set up transparent
peer-to-peer routing between two remotes in a point-to-multipoint or store-and-forward system by loading
specific MAC addresses in each radio’s remote transparent destination address.

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3.0 DNT90 Application Interfaces
A DNT90 module provides a variety of application interfaces including two serial ports, an SPI port, six
digital I/O ports (logic state), three 12-bit ADC input ports, and two 12-bit DAC output ports. Each of these
interfaces is discussed below.
3.1 Serial Ports
The DNT90 includes two serial ports, one for communication and an optional one for diagnostics. The
communication port is a full-duplex UART interface with hardware flow control on two of the digital I/O
pins an optional feature. One digital I/O pin can also be configured as an RS485 enable function. The se-
rial communication port can be configured with baud rates from 1.2 to 250 kbps, with 9.6 kbps the default
baud rate. The DNT90 communication port transmits/receives 8-bit data with a choice of even, odd or no
parity and 1 or 2 stop bits. The default configuration is no parity and one stop bit. See Section 5.1 for rec-
ommendations on configuring the communication port, and Section 7.4.4 for detailed information on con-
figuration parameters. The diagnostic port is enabled as an alternate function on two digital I/O pins, and
can be configured with baud rates from 1.2 to 250 kbps, with 9.6 kbps the default baud rate. The diagnos-
tic port transmits/receives 8-bit data with no parity and 1 stop bit. See Section 7.4.8 for diagnostic port
configuration details.
3.2 SPI Port
The DNT90 serial peripheral interface (SPI) port can operate either as a master or a slave. The port
includes the four standard SPI connections - MISO, MOSI, SCLK and /SS, plus three signals used to
support SPI slave mode operation - /HOST_RTS, /HOST_CTS and DAV. The serial port and SPI master
mode can run simultaneously. Serial port operation is disabled when the SPI port is configured for slave
mode. Note that all SPI slave mode messages must be protocol formatted.
D N T 0P e r i p h e r a l
D N T 0 S P I M a s t e r M o d e S i g n a l i n g
/ S S
S C L K
M O S I
M I S O
Figure 3.2.1
The DNT90 SPI port can run at three clock rates in master mode - 125, 250 or 500 kbps. There are two
message sources available to a DNT90 SPI master, a protocol-formatted RxData message or a stored
command. The DNT90 master will clock a message from either source into its slave and return the bytes
clocked out as a protocol-formatted TxData message. The DNT90 event timer triggers sending the stored
command to the DNT90’s slave. The stored command can be up to 16 bytes in length. Figure 3.2.1

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shows the required SPI master mode-signal connections, and Figure 3.2.2 shows the SPI master-mode
timing.
/ S S
S C L K
M O S I
M I S O
S P I B i t C l o c k
C o m m a n d t o S l a v e
D a t a f r o m S l a v e
D N T 0 S P I M a s t e r M o d e O p e r a t i o n
Figure 3.2.2
In SPI slave mode, the host can stream data into DNT90 at up to 250 kbps, provided the host suspends
clocking within 10 bytes following a low-to-high transition on /HOST_CTS. The host can clock data into
the DNT90 at up to 4 Mbps for data bursts of up to 50 bytes, provided the interval from the end of one
burst to the start of the next burst is at least 2 ms, and the host suspends clocking on a low-to-high transi-
tion on /HOST_CTS. See Figure 3.2.4
D N T 0H o s t
D N T 0 S P I S l a v e M o d e S i g n a l i n g
/ S S
S C L K
M O S I
M I S O
/ H O S T _ C T S
DAV
/ H O S T _ R T S
Figure 3.2.3

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/ S S
/ H O S T _ C T S
S C L K
M O S I
S P I B i t C l o c k
M e s s a g e t o D N T 0
D N T 0 S P I S l a v e M o d e M e s s a g e L o a d
Figure 3.2.4
The host should use the following steps to fetch data from a DNT90 SPI slave, as show in Figure 3.2.5:
1. The host sets the /HOST_RTS signal high to allow the DNT90 to signal data available.
2. The DNT90 sets the data available (DAV) high to signal the host it has data.
3. The host set the /SS signal low to enable SPI operation.
4. The host clocks in one dummy byte (ignore the output byte) and then sets /HOST_RTS low.
5. The host begins to clock out the data, which can include several messages.
6. The host continues to clock out data until a 0x00 byte occurs in the byte stream where a 0xFB
start-of-message would be expected.
7. The host has now clocked out all messages and the 0x00 is discarded.
8. The host sets /HOST_RTS and /SS high to allow the DNT90 to signal DAV the next time it
has data.
Note that the DAV signal can go low before the last message is clocked out. It is not a reliable indication
that the last byte of the message(s) has been clocked out. See Section 5.2 for recommendations on con-
figuring the SPI port, and Section 7.4.4 for detailed information on SPI port configuration parameters.
/ S S
DAV
S C L K
M I S O
S P I C l o c k
P r o t o c o l F o r m a t t e d R X M e s s a g e
D N T 0 S P I S l a v e M o d e R X M e s s a g e R e t r i e v a l
L e n g t h B y t e
0 x F B S t a r t o f M e s s a g e
/ H O S T _ R T S
Figure 3.2.5

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3.3 Digital I/O
The DNT90’s six digital (state) I/O ports are labeled GPIO0 through GPIO5. GPIO5 has an alternate func-
tion of /HOST_ RTS and GPIO4 of /HOST_CTS, providing hardware handshaking for the serial port and
SPI slave mode operation. If serial port hardware handshaking is not required and SPI slave mode is not
enabled, GPIO4 and GPIO5 can be used for other digital I/O functions. When SPI slave mode is enabled,
GPIO5 and GPIO4 must be used for /HOST_RTS and /HOST_CTS respectively, and GPIO3 must be
used to provide the DAV signal (SPI slave mode overrides any other configuration for these ports). Ex-
cept in SPI slave mode, GPIO0 through GPIO5 are available for customer-defined functions:
- The direction of each GPIO pin can be set for both active and sleep modes.
- The initial state (power on) of all GPIO pins configured as outputs can be set.
- The state of all GPIO pins configured as outputs in sleep mode can be set.
- GPIO triggering of I/O event reporting can be configured.
- GPIO level control of sleep hold-off can be configured.
See Section 5.3 for recommendations on configuring the digital I/O, and Sections 7.4.6 and 7.4.7 for de-
tailed information on GPIO parameters.
3.4 Analog I/O
The DNT90’s three ADC input channels are labeled ADC0 through ADC2. The ADC can be disabled if
unused to reduce current consumption. The ADC can be operated in either single-ended mode or differ-
ential mode. In single-ended mode, up to three sensor inputs can be measured. The negative sensor in-
puts are connected to ground and the positive sensor inputs are connected to ADC0, ADC1 and ADC2
respectively. Single-ended measurements are unsigned 11-bit values. In differential mode, one or two
sensor inputs can be measured as 12-bit signed values. The first differential measurement is the differ-
ence between the voltage on ADC1 and the voltage on ADC0, and is referred to as the ADC0 differential
measurement. The second differential measurement is the difference between ADC2 and ADC0, and is
referred to as the ADC1 differential measurement. Operating the ADC in differential mode takes ad-
vantage of common mode rejection to provide the best measurement stability. Differential mode also in-
corporates a programmable gain preamplifier function, with gains settings from 1 to 64 available.
There are two options for the ADC full-scale reference:
1. The DNT90 regulated supply voltage divided by 1.6, or about 2.06 V
2. A low impedance voltage source applied to the DNT90’s ADC_EXT_REF input pin, 2.7 V maxi-
mum. If no connection is made to this pin, a voltage equal to about 2.7 V will be present.
Note that when differential ADC mode is used, the maximum output voltage available from the preamplifi-
er at any gain setting is 2.4 V, so the maximum ADC reading that can be made using a 2.7 V ADC refer-
ence will be about 88.9% of full scale. The ADC channels are read each ADC sample interval, which is
configurable. High and low measurement thresholds can be set for each ADC channel to trigger I/O event
reporting messages.

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The DNT90’s two DAC outputs are labeled DAC0 and DAC1. The DACs can be disabled if unused to re-
duce current consumption. The DAC settings have 12-bit resolution. There are two options for the DAC
full-scale reference:
1. The DNT90 regulated supply voltage, about 3.3 V
2. A low impedance voltage source applied to the DNT90’s ADC_EXT_REF input pin, 2.7 V maxi-
mum. If no connection is made to this pin, a voltage equal to about 2.7 V will be present.
See Section 5.4 for recommendations on configuring the analog I/O, and Sections 7.4.6 and 7.4.7 for de-
tailed information on analog I/O parameters.
3.5 I/O Event Reporting and I/O Binding
The DNT90’s I/O event reporting function can generate a protocol-formatted RxEvent message when
triggered by one of the following I/O events:
- A specific state change of GPIO0, GPIO1, GPIO2 or GPIO3.
- Firing of the periodic event report timer.
- A high or low threshold exceeded on a measurement by ADC0, ADC1 or ADC2.
An I/O report message includes:
- The states of GPIO0 through GPIO5.
- The latest measurements made by ADC0 through ADC2 .
- A set of flags indicating which event(s) triggered the I/O report.
- The settings of DAC0 and DAC1.
The I/O binding function works in conjunction with I/O event reporting. When I/O binding is enabled on a
DNT90, data received in an I/O event report it is mapped as follows:
- GPIO2 will output the state of GPIO0 in the last received event report.
- GPIO3 will output the state of GPIO1 in the last received event report.
- DAC0 will output the voltage read by ADC0 in the last received event report.
- DAC1 will output the voltage read by ADC1 in the last received event report.
I/O binding is used to transmit switch positions or analog signals from one location to another. Note that
I/O binding cannot be used in a DNT90 when SPI slave mode is enabled or differential ADC mode is
used. See Section 5.4 for recommendations on configuring I/O event reporting and binding, and Sections
7.4.6 and 7.4.7 for detailed information on I/O reporting and binding parameters.

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4.0 DNT90 System Configuration
DNT90 radios feature an extensive set of configuration options that allows them to be adapted to a wide
range of applications. Configuration defaults have been carefully selected to minimize the configuration
effort for most applications, while providing the ability to individually adjust the configuration of each radio
to achieve highly optimized system operation.
4.1 Configuration Parameters
The configuration of a DNT90 is controlled by a set of parameters (registers). Parameters that address a
particular aspect of operation are grouped into a bank. All parameters can be accessed through a mod-
ule’s serial port and over the radio link. Most parameters are read/write. Read-only parameters include
fixed values such a MAC addresses, firmware version numbers and parameters that are dynamically ad-
justed during system operation such as link status. Write-only parameters include security keys and cer-
tain action triggers such as reset. Incorrectly configuring certain parameters can disable a module’s radio
link, but the configuration can always be corrected through the serial port. The organization of the param-
eter register banks and the details of each parameter are covered in Section 7.4 of this guide. Sections
4.2 through 5.7 discuss which parameters apply to various aspects of configuring a DNT90 system, net-
work or application interface.
4.2 Configuring a Basic Point-to-Point System
A basic DNT90 point-to-point system is suitable for many serial data applications. The default config-
uration of a DNT90 is a remote with the serial port configured for transparent operation at 9.6 kbps,
8N1. To configure a basic point-to-point system:
1. Configure one of the modules as a base by setting the DeviceMode parameter in Bank 0 to 0x01.
2. Set the MemorySave parameter in Bank 0xFF to 0xD2, which will save the DeviceMode parame-
ter to EEPROM and reset the module, enabling base operation.
3. All other parameters may be left at their default values.
4.3 Configuring a Basic Point-to-Multipoint Point System
A basic DNT90 point-to-multipoint point systems is suitable for many serial data applications where
multiple remotes are used. The default configuration of a DNT90 is a remote with the serial port con-
figured for transparent operation at 9.6 kbps, 8N1. To configure a basic point-to-multipoint system:
1. Configure one of the modules as a base by setting the DeviceMode parameter in Bank 0 to 0x01.
2. If the host application driving the base will individually communicate each remote, set the Proto-
colMode parameter in Bank 4 of the base to 0x01. This step is not required if messages from the
base to the remotes will always be broadcast and/or the base does not need to know the MAC
address of the remote sending a message.
3. Set the MemorySave parameter in Bank 0xFF to 0xD2, which will save the DeviceMode parame-
ter to EEPROM and reset the module, enabling base operation.
4. All other parameters may be left at their default values.

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5. If the host application driving the base will individually communicate each remote, read or scan
the MAC addresses from the label on top of each remote and load the addresses in the host ap-
plication data base.
4.4 Configuring a Customized Point-to-Point or Point-to-Multipoint System
The DNT90 includes many configuration parameters that allow extensive customization of a point-to-point
or point-to-multipoint system. Most applications will require only a few of these parameters be changed
from their default values. But for those applications that need them, RFM recommends the following con-
figuration sequence. Skip the configuration steps where the default parameter value is satisfactory.
1. Configure one of the modules as a base by setting the DeviceMode parameter in Bank 0 to 0x01.
2. Set the optional AES security key in all system radios by loading your selected 16-byte string into
the SecurityKey parameter in Bank 0 (the default is 16 bytes of 0x00).
3. Select the frequency band of operation by setting the FrequencyBand parameter in Bank 1 of the
base radio as desired (the default is Band 0).
4. Set the transmitter power level as needed in all radios by setting the TxPower parameter in
Bank 0 (the default is 158 mW).
5. Configure the system ID in all radios by setting the SystemID parameter in Bank 0 (the default is
OK if there is no chance of overlapping systems).
6. Load the parent network ID in all remotes in the ParentNetworkID parameter in Bank 0 as needed
(wildcard default is OK for point-to-point and point-to-multipoint systems).
7. Set the BaseModeNetID parameter in the base to match the ParentNetworkID parameter in the
remotes if the default BaseModeNetID is not used in the base and the wildcard default Parent-
NetworkID is not used in the remotes.
8. For a point-to-multipoint system where DNT90 MAC addressing will be used, set the Proto-
colMode parameter in Bank 4 of the base to 0x01. Set the protocol mode as needed in the base
and remote of a point-to-point system, and as needed in the remotes in a point-to-multipoint sys-
tem. If SPI slave mode will be used, protocol mode must be enabled in all system radios. Note
that if the application data includes addressing information for individual remote hosts, the DNT90
broadcast mode can be used instead of the DNT90 protocol mode.
9. If using transparent serial mode in the system:
a. Set the remote transparent destination address in the RmtTransDestAddr parameter,
Bank 0, in each remote if the destination is not the base (the base address is the default
destination).
b. Set the transparent point-to-point mode to select either the RmtTransDestAddr address
(default) or the address of the originator of the last received message as the remote des-
tination address. The parameter that controls this destination address is the Trans-
PtToPtMode in Bank 4. Set in all remotes as needed.
c. Set the timeout for transmission of transparent data in the remotes as needed. The pa-
rameter that controls the timeout is the TxTimeout in Bank 4 (the default is no timeout).

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d. Set the minimum message length for transmission of transparent data in the remotes as
needed. The parameter that controls the length is the MinPacketLength in Bank 4 (the
default is one byte).
10. Refer to Section 4.6 below which discusses how to coordinate the values of the following four
parameters:
a. Set the maximum number of messages that can be sent in a hop on each system radio.
The parameter that controls this number is MsgsPerHop in Bank 4. The default is 8 mes-
sages.
b. Load the required base slot size into the BaseSlotSize parameter, Bank 1, in the base.
The default is 40 bytes.
c. Configure the number of child slots per hop on the base by setting the NumSlots parame-
ter. The default is 3 slots.
d. Set the required hop duration on the base. The HopDuration parameter in Bank 0 con-
trols hop duration. The default is 20 ms.
11. Configure the slot lease on the base by setting the SlotLease parameter. The default is 4 hops.
12. Set the heartbeat interval as required in each system radio. The parameter that controls heart-
beats is the HeartBeatIntrvl in Bank 0. The default is 20 seconds/heartbeat.
13. Enable end-to-end message ACKs where required by setting the EndToEndAckEnable parameter
in Bank 0 to 1. Enabling this parameter provides a confirmation that a message has reached its
destination in peer-to-peer or store-and-forward routing. The default is disabled.
14. Set the message retry limit on the base with the ArqAttemptLimit parameter in Bank 1. The de-
fault value is 6 retries.
15. Set the link drop threshold on the base by setting the LinkDropThreshold in Bank 1. This parame-
ter sets the number of sequential hops without receiving a beacon that will trigger a child to re-
synchronize and re-link to its parent. The default is 10 hops.
16. Set the point-to-point reply timeout on the base in the P2PReplyTimeout parameter in Bank 1.
The default is 16 hops. See Section 7.4.2 for parameter details.
17. Configure the registration timeout on the base by setting the RegistryTimeout parameter in
Bank 1. The default timeout is 50 hops. See Section 7.4.2 for a discussion of this parameter.
18. Load an optional “friendly description” in each system radio in the UserTag parameter, Bank 0.
4.5 Configuring a Store-and-Forward System
The following additional parameters must be set to configure a DNT90 store-and-forward system:
1. Configure the DNT90 radios designated to be routers by setting the DeviceMode parameter
in Bank 0 to 0x02.
2. Enable store-and-forward operation on all system radios by setting the Store&ForwardEn
parameter in Bank 0 to 0x01.