RFM DNT24C Quick setup guide

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DNT24 Series
2.4 GHz Spread Spectrum
Wireless Transceivers
Integration Guide

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Important Regulatory Information
RFM Product FCC ID: HSW-DNT24
IC 4492A-DNT24
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 into 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:
The DNT24 has been designed to operate with any dipole antenna of up to 12 dBi of gain, any corner
reflector antenna of up to 14 dBi gain, any patch antenna of up to 12 dBi gain, or any chip antenna of up
to 1.7 dBi gain. 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.
IC RSS-210 Detachable Antenna Gain Restriction:
This radio transmitter, IC 4492A-DNT24, has been approved by the Industry Canada to operate with the
antenna types listed below with the maximum permissible gain and the required antenna impedance for
each antenna type indicated. Antenna types not included in this list, having a gain greater than the maxi-
mum gain indicated for that type, are strictly prohibited for use with this device.
Le présent émetteur radio IC 4492A-DNT24 a été approuvé par Industrie Canada pour fonctionner
avec les types d'antenne énumérés ci-dessous et ayant un gain admissible maximal et l'impédance
requise pour chaque type d'antenne. Les types d'antenne non inclus dans cette liste, ou dont le gain est
supérieur au gain maximal indiqué, sont strictement interdits pour l'exploitation de l'émetteur.
Type Model Number Gain Impedance
Omnidirectional OD12-2400 12 dBi 50 ohm
Corner SCR14-2400CT 14 dBi 50 ohm
Patch PA2412 12 dBi 50 ohm
Chip FR05-S1-N-0-102 1.7 dBi 50 ohm

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Under Industry Canada regulations, this radio transmitter may only operate using an antenna of a type
and maximum (or lesser) gain approved for the transmitter by Industry Canada. To reduce potential radio
interference to other users, the antenna type and its gain should be so chosen that the equivalent isot-
ropically radiated power (e.i.r.p.) is not more than that permitted for successful communication.
Conformément à la réglementation d'Industrie Canada, le présent émetteur radio peut fonctionner
avec une antenne d'un type et d'un gain maximal (ou inférieur) approuvé pour l'émetteur par Industrie
Canada. Dans le but de réduire les risques de brouillage radioélectrique à l'intention des autres
utilisateurs, il faut choisir le type d'antenne et son gain de sorte que la puissance isotrope rayonnée
équivalente (p.i.r.e.) ne dépasse pas l'intensité nécessaire à l'établissement d'une communication sat-
isfaisante.
This device complies with Industry Canada licence-exempt RSS standard(s). 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.
See Section 6.8 of this manual for regulatory notices and labeling requirements. Changes or modifica-
tions to a DNT24 not expressly approved by RFM may void the user’s authority to operate the module.

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Table of Contents
1.0 DNT24 Introduction.......................................................................................................................... 6
1.1 Why Spread Spectrum? ............................................................................................................ 6
1.2 Frequency Hopping versus Direct Sequence ........................................................................... 7
2.0 DNT24 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 DNT24 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 DNT24 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 DNT24 System Configuration ........................................................................................................ 17
4.1 Configuration Parameters ....................................................................................................... 17
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 ................................ 18
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 DNT24 Application Interface Configuration ................................................................................... 23
5.1 Configuring the Serial Port ...................................................................................................... 23
5.2 Configuring the SPI Port ......................................................................................................... 23
5.3 Configuring Digital I/O ............................................................................................................. 23
5.4 Configuring Analog I/O ............................................................................................................ 23
5.5 Configuring I/O Event Reporting and I/O Binding ................................................................... 24
5.6 Configuring Sleep Mode.......................................................................................................... 25
6.0 DNT24 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 DNT24 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........................................................................................ 46
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................................................................................................... 51
7.4.8 Bank 0x0FF - Special Functions....................................................................................... 56
7.5 Protocol-formatted Message Examples .................................................................................. 57
7.5. 1 Data Message................................................................................................................... 57
7.5.2 Configuration Messages ................................................................................................... 58
7.5.3 Sensor Message............................................................................................................... 58
7.5.4 Event Message ................................................................................................................. 59
8.0 DNT24DK/DNT24ADK Developer’s Kits ....................................................................................... 60
8.1 Kit Contents............................................................................................................................. 60
8.2 Additional Items Needed ......................................................................................................... 60
8.3 Developer’s Kit Default Operating Configuration .................................................................... 60
8.4 Developer’s Kit Hardware Assembly....................................................................................... 61
8.5 Utility Program......................................................................................................................... 62
8.6 Initial Kit Operation .................................................................................................................. 62
8.6.1 Serial Communication and Radio Configuration .............................................................. 65
8.7 Interface Board Features ........................................................................................................ 72
9.0 Troubleshooting ............................................................................................................................. 74
9.1 Diagnostic Port Commands .................................................................................................... 74
10.0 Appendices .................................................................................................................................... 75
10.1 Ordering Information ............................................................................................................... 75
10.2 Technical Support ................................................................................................................... 75
10.3 DNT24 Mechanical Specifications .......................................................................................... 76
10.4 DNT24 Development Board Schematic .................................................................................. 80
11.0 Warranty ........................................................................................................................................ 83

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1.0 DNT24 Introduction
DNT24 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
operation in the 2.4 GHz ISM band allows license-free use in most regions of the world. The DNT24 sup-
ports serial data rates for host communications from 1.2 to 250.0 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 DNT24 features include:
•Multipath fading resistant frequency hopping
technology with up to 24 frequency chan-
nels, 2406 to 2475 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 250.0 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 DNT24 configura-
tion when powered off
•Five mile plus range with omnidirectional
antennas (antenna height dependent)
•Selectable 10 or 63 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
other 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
domain, 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 multi-
path 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 DNT24 System Overview
A DNT24 radio can be configured to operate in one of three modes - base, remote or router. A base con-
trols a DNT24 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 DNT24 system contains at least one network. The simplest DNT24 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,
DNT24 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 DNT24 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 organ-
ized as a time division multiple access (TDMA) frame. A DNT24 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 2 4 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

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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
keeps its data queued and continues to look for an open slot in each beacon until at least one slot
becomes available. The access method the DNT24 uses is referred to as Ad Hoc TDMA.
2.5 DNT24 Addressing
Each DNT24 has a unique MAC address. The MAC address can be read or bar-code scanned from the
label on top of each radio. A DNT24 radio in any mode (base/router/remote) can be addressed using its
MAC address. A DNT24 base can be addressed using either its MAC address or address 0x000000. A
DNT24 can send a message to all other DNT24’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 DNT24 radios hold a system ID that can be used to distinguish systems that physically overlap. In a
DNT24 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 Parent-
MacAddress 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 DNT24 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 col-
lected by child radios, allowing them to register with a parent, and to later follow any control parameter

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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 DNT24 system.
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
- use no more hops in the hopping pattern than are necessary
- transmit only dynamic cycle parameters once system nodes have static parameters
In the United States and Canada, the DNT24 complies with DTS (DSSS) regulations based on the band-
width of its transmitted spectrum. In this case, frequency hopping is optional and when frequency hopping
is used there is no minimum requirement on the number of hopping channels that can be used. As dis-
cussed in Section 7.4.2., there are two 5-channel hopping patterns that can be used to help minimize link-
ing time. All DNT24’s in a system must be preset to one of these 5-channel hopping patterns in order to
achieve fast linking. Note that the 5-channel hopping patterns cannot be used in Europe.
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 DNT24 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 DNT24 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 or in multi-point systems when
broadcast addressing is used, the base can also be configured for transparent serial port operation.
In all other cases, serial data will 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.

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Transparent data is routed using a remote transparent destination address. In a remote, this address
defaults to the base, 0x000000, and in the base this address defaults to broadcast, 0xFFFFFF. These
defaults 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.
3.0 DNT24 Application Interfaces
A DNT24 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 DNT24 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 as an optional feature. One digital I/O pin can also be configured as an RS485 enable function. The
serial communication port can be configured with baud rates from 1.2 to 250.0 kbps, with 9.6 kbps the
default baud rate. The DNT24 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 recommendations on configuring the communication port, and Section 7.4.4 for detailed informa-
tion on configuration 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 250.0 kbps, with 9.6 kbps the default baud rate.
The diagnostic port transmits/receives 8-bit data with no parity and 1 stop bit. See Section 7.4.8 for diag-
nostic port configuration details.
3.2 SPI Port
The DNT24 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 9 0 0P e r i p h e r a l
D N T 2 4 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

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The DNT24 SPI port can run at three clock rates in master mode - 125, 250 or 500 kbps. There are two
message sources available to a DNT24 SPI master, a protocol-formatted RxData message or a stored
command. The DNT24 master will clock a message from either source into its slave and return the bytes
clocked out as a protocol-formatted TxData message. The DNT24 event timer triggers sending the stored
command to the DNT24’s slave. The stored command can be up to 16 bytes in length. Figure 3.2.1
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 2 4 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 DNT24 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 DNT24 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 9 0H o s t
D N T 2 4 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 9 0
D N T 2 4 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 DNT24 SPI slave, as show in Figure 3.2.5:
1. The host sets the /HOST_RTS signal high to allow the DNT24 to signal data available.
2. The DNT24 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 DNT24 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
D A V
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 2 4 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 DNT24’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).
Except 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
detailed information on GPIO parameters.
3.4 Analog I/O
The DNT24’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
inputs 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 advan-
tage of common mode rejection to provide the best measurement stability. Differential mode also incorpo-
rates 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 DNT24 regulated supply voltage divided by 1.6, or about 2.06 V
2. A low impedance voltage source applied to the DNT24’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 preampli-
fier 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.
The DNT24’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 DNT24 regulated supply voltage, about 3.3 V

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2. A low impedance voltage source applied to the DNT24’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
detailed information on analog I/O parameters.
3.5 I/O Event Reporting and I/O Binding
The DNT24’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
DNT24, 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 DNT24 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.
4.0 DNT24 System Configuration
DNT24 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 DNT24 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
adjusted during system operation such as link status. Write-only parameters include security keys and
certain 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

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parameter register banks and the details of each parameter are covered in Section 7.4 of this guide. Sec-
tions 4.2 through 5.7 discuss which parameters apply to various aspects of configuring a DNT24 system,
network or application interface.
4.2 Configuring a Basic Point-to-Point System
A basic DNT24 point-to-point system is suitable for many serial data applications. The default con-
figuration of a DNT24 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 DNT24 point-to-multipoint point systems is suitable for many serial data applications where
multiple remotes are used. The default configuration of a DNT24 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.
5. If the host application driving the base will individually communicate with each remote, the MAC
address for each remote can be obtained from announce packets, heartbeat packets, a ForceDis-
cover command, or by reading or scanning the MAC address from the label on top of each re-
mote.
4.4 Configuring a Customized Point-to-Point or Point-to-Multipoint System
The DNT24 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).

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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 63 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 DNT24 MAC addressing will be used, set the Protocol-
Mode 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 system. 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 DNT24 broad-
cast mode can be used instead of the DNT24 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 to send as
soon as possible).
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.

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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
resynchronize 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 DNT24 store-and-forward system:
1. Configure the DNT24 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.
3. In each router, load a unique base-mode network ID into the BaseModeNetID parameter in Bank
0, and into the base if a router is set to 0x00.
4. To configure a specific system topology, set the parent network ID parameter, ParentNwkID, and
optionally the alternate parent network ID parameter, AltParentNwkID, in all routers and
remotes. Note that a store-and-forward system topology can be formed either automatically or
manually, based on the settings of the ParentNetworkID and optionally the AltParentNwkID
parameters:
- Setting the ParentNwkID parameter to 0xFF in all routers and remotes allows each
router and remote to automatically link to a parent, causing the system to form
automatically (child routers picking each other as a parent cannot occur). In this case, the
AltParent-NwkID parameter should be set to 0xFF, which disables it.