Laird RM024 User manual

RAMP Wireless Module
RM024
User Manual
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RM024 User Manual
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CONN-GUIDE-RAMP24-0413
REVISION HISTORY
Rev.
Revision Date
Description
1.0
Initial Version
2.1
Added firmware changes, updated the name of the Force 9600 Pin,
removed old references to LT2510 part numbers, added new information
on cyclic sleep and Antenna Switch Override. Added a table under Max
Power and a table for the Set Max Power command.
2.2
Minor grammatical fixes.
2.3
27 June 2013
PWM output data was corrected to a 39.3846 µS period vs. 315.077, as
was stated previously.
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CONTENTS
Contents..................................................................................................................................................... 3
RAMP Modules .......................................................................................................................................... 4
Overview ............................................................................................................................................................. 4
Key Features ........................................................................................................................................................ 4
Detailed Specifications......................................................................................................................................... 5
Pin Definitions...................................................................................................................................................... 6
Input Characteristics ............................................................................................................................................ 7
Output Characteristics ......................................................................................................................................... 7
Block Diagram ...................................................................................................................................................... 8
Timing Specifications ........................................................................................................................................... 8
RF Hop Frame ...................................................................................................................................................... 9
Hardware Interface ................................................................................................................................. 10
Pin Descriptions ................................................................................................................................................. 10
Theory of Operation................................................................................................................................ 12
Server/Client Architecture ................................................................................................................................. 12
Adjustable RF Data Rate..................................................................................................................................... 12
Modes of Operation........................................................................................................................................... 13
Serial Interface Baud Rate .................................................................................................................................. 14
Interface Timeout/RF Packet Size....................................................................................................................... 15
Flow Control ...................................................................................................................................................... 16
Radio Configurations.......................................................................................................................................... 17
EEPROM Parameters................................................................................................................................ 26
Configuring the RM024........................................................................................................................... 36
AT Commands.................................................................................................................................................... 36
Utility Commands .............................................................................................................................................. 38
Status Commands .............................................................................................................................................. 40
Command Descriptions ...................................................................................................................................... 41
Serial Firmware Upgrades ....................................................................................................................... 48
Overview ........................................................................................................................................................... 48
Upgrading Via Windows OEM Configuration Utility............................................................................................ 48
Upgrading FW Commands ................................................................................................................................. 49
Command Descriptions ...................................................................................................................................... 49
Process to Manually Upgrade RM024 ................................................................................................................ 51
API Operation .......................................................................................................................................... 52
API Send Data Complete .................................................................................................................................... 52
API Receive Packet............................................................................................................................................. 52
API Transmit Packet ........................................................................................................................................... 53
Mechanical Considerations ..................................................................................................................... 54
Mechanical Drawing .......................................................................................................................................... 54
Note on Mechanical Drawings: .......................................................................................................................... 54
Ordering Information.............................................................................................................................. 57
Product Part Numbers ....................................................................................................................................... 57
Regulatory Information........................................................................................................................... 58
FCC/IC Requirements for Modular Approval ...................................................................................................... 58
RM024 Firmware History ................................................................................................................................... 60
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RAMP MODULES
Laird Technologies RAMP (Range Amplified MultiPoint) modules are designed to provide robust wireless
communications for any number of applications requiring a wireless transport for serial data. RAMP modules
feature a Frequency Hopping Spread Spectrum (FHSS) protocol for excellent interference and multipath
immunity. RAMP modules Server/Client architecture allows for more than 16 million clients to be addressed
and communicating within the network.
Overview
The RM024 RAMP module is based on Laird Technologies LT2510 core technology, enhanced with a new RF
front end for improved sleep, improved link budget and a switchable antenna output. The RM024 is available
in two versions, one with 125 mW maximum conducted output power and approved for North American and
similar markets and one with 50 mW maximum conducted output power and approved for European and
similar markets. These modules are identical except for output power, transmit power consumption, and the
number of RF Channels available. Differences between the two versions, where applicable, will be denoted
based on part number.
This document contains information about the hardware and software interface between a Laird
Technologies RM024 transceiver and an OEM Host. Information includes the theory of operation,
specifications, interface definitions, configuration information, and mechanical drawings.
Note: Unless mentioned specifically by name, the RM024 modules will be referred to as “radio” or
“transceiver”. Individual naming is used to differentiate product specific features. The host
(PC/Microcontroller/Any device to which the RM024 module is connected) will be referred to as
“OEM Host” or “Host.”
Key Features
Retries and acknowledgements
Configurable network parameters
Multiple generic I/O
280 kbps or 500 kbps RF data stream
Idle current draw of 9.5 mA, sleep current of 50 uA
Software selectable interface baud rates from 1200 bps to 460.8 kbps
Upgradable FW through serial port
Low cost, low power, and small size ideal for high volume, portable, and battery powered applications
All modules are qualified for Industrial temperatures (-40°C to 85°C)
Advanced configuration available using AT commands
Easy to use Configuration and Test Utility software
Switchable antenna output, either integrated antenna or external antenna through U.FL
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Detailed Specifications
Table 1: Detailed Specifications
GENERAL
Form Factor
SMD-ANT+U.FL, Pluggable-ANT+U.FL, SMD-U.FL,
Pluggable-U.FL
Antenna
External antenna through U.FL connector or dual
antenna with integrated antenna and U.FL
Serial Interface Data Rate
Baud rates from 1200 bps to 460800 bps. Non-standard
baud rates are also supported.
Channels
FCC: 43 or 79 selectable channels
CE: 43 selectable channels
Security
Channelization, System ID, and Vendor ID
Minimum Flash (EEPROM) Memory Endurance
1000 Write/Erase Cycles
TRANSCEIVER
Frequency Band
2400 –2483.5 MHz
RF Data Rate (Raw)
280 kbps or 500 kbps selectable
Hop Bin Spacing
900 kHz over 79 hops
1500 kHz over 43 hops
RF Technology
Frequency Hopping Spread Spectrum
Modulation
MSK
Maximum Output Power Conducted1
FCC: +5 to +21 dBm selectable
CE: +3.5 to +18 dBm selectable
Supply Voltage
2.3 –3.6 V ± 50 mV ripple
Current Draw2
100% Tx
166 mA
85 mA
1/8 Tx (when selected)
40 mA
40 mA
100% Rx
36 mA
36 mA
Rx average (idle current)
9.5 mA
11.6 mA
Deep sleep
50 µA
50 µA
Receiver Sensitivity (1% PER)
-95 dBm at 280 kbps RF Data Rate
-94 dBm at 500 kbps RF Data Rate
Range (based on external 2.0 dBi antenna at
280 kbps RF Data Rate)3
Outdoor (line-of-sight)
Indoor (estimated)
FCC
2.5 miles (4 km)
1300 ft (400 m)
CE
1.5 miles (2.4 km)
790 ft (240 m)
ENVIRONMENTAL
Temperature (Operational)
-40ºC to 85ºC
Temperature (Storage)
-50ºC to 150ºC
PHYSICAL
SMD-Multi Antenna Dimensions
1.0” x 1.54” x 0.14” (25.4 mm x 39 mm x 3.6 mm)
SMD-U.FL Dimensions
1.0” x 1.28” x 0.14” (25.4 mm x 32.4 mm x 3.6 mm)
Pluggable-Multi Antenna Dimensions
1.05” x 1.56” x 0.44” (26.7 mm x 39.6 mm x 11.3 mm)
Pluggable-U.FL Dimensions
1.05” x 1.29” x 0.42” (26.7 mm x 33 mm x 10.6 mm)
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CERTIFICATIONS
FCC Part 15.247
KQL-RM024
Industry Canada (IC)
2268C-RM024
CE
Yes, RM024-x50-x versions
RoHS
Yes
Japan (TELEC) 4
Yes
Brazil (Anatel)5
None
1. Maximum Output power stated, step measurements for power could vary by +/- 2.0 dBm.
2. Sleep currents are estimated
3. Range distances are estimated, measurements were taken at 4.1 miles with 5 dBi antenna for FCC
module
4. See Regulatory Information in this manual
5. Contact your sales representative for more details.
Pin Definitions
Table 2: Pin Definitions
SMT Pin
Pluggable Pin
Type
Signal Name
Functions
1
7
O
GIO_0
Generic Output / Hop_Frame
2
6
O
GIO_1
Generic Output
3
8
DNC
Do Not Connect
4
17
O
GIO_2
RS485 Driver Enable
5
19
O
GIO_3
PWM Output
6
3
I
RXD
Asynchronous serial data input to transceiver
7
2
O
TXD
Asynchronous serial data output from transceiver
8
10
GND
GND
Signal Ground
9
1
PWR
Vcc
2.3 –3.6 V ±50 mV ripple (must be connected)
10
-
PWR
Vpa
2.3 - 3.6 V ±5 0mV ripple (must be connected)
11
-
GND
GND
Signal Ground
12
9
I
Force 9600
/Sleep Interrupt
Force 9600 –When pulled logic Low and then
applying power or resetting, the transceiver’s
serial interface is forced to a 9600, 8-N-1 rate.
Sleep Interrupt- When taken low this pin will
wake the radio from sleep
Note: Because this mode disables some modes
of operation, it should not be
permanently pulled Low during normal
operation.
13
14
I
GIO_4
Generic Input
14
5
I
µP_Reset
RESET –Controlled by the RM024 for power-on
reset if left unconnected. After a stable power-on
reset, a logic Low pulse will reset the transceiver.
15
11
I
CMD/Data
When logic Low, the transceiver interprets
incoming OEM Host data as command data.
When logic High, the transceiver interprets OEM
Host data as transmit data.
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SMT Pin
Pluggable Pin
Type
Signal Name
Functions
16
15
O
In Range
When logic Low, the client is in range and
synchronized with a server. This will always be
Low on a server.
17
16
I
RTS
Request to Send. Floats high if left unconnected.
When enabled in EEPROM, the module will not
transmit data out the Serial UART unless the pin is
Low.
18
12
O
CTS
Clear to Send - CTS is used for hardware flow
control. CTS will toggle high when the input
buffer reaches the CTS On threshold until the
buffer recedes below CTS Off.
19
18
GIO_8
Generic Input1
20
13
GIO_5
Reserved for future use. Do not connect.
21
4
GIO_6
Reserved for future use. Do not connect.
22
20
I
GIO_7
Analog to Digital Input
Tips:
All I/O matches the Vcc.
All inputs are weakly pulled High via a 20k Ohm pull-up resistor and may be left floating during normal
operation
Minimum Connections: VCC, VPA, GND, TXD, & RXD
Signal direction is with respect to the transceiver
Unused pins should be left disconnected
Input Characteristics
Table 3: Input Characteristics
Signal Name
High Min.
High Max.
Low Min.
Low Max.
µP_Reset
0.8 v
Vcc
0 v
0.6 v
RTS
2.31 v
Vcc
0 v
.99 v
AD_In
N/A
Vcc
0 v
N/A
All other inputs
70% Vcc
Vcc
0 v
30% Vcc
Output Characteristics
Table 4: Output Characteristics
Signal Name
High Min.
High Max.
Low Min.
Low Max.
Sink Current
GO_0
2.5 v
3.3 v
0 v
0.4 v
20 mA
GO_1
2.5 v
3.3 v
0 v
0.4 v
20 mA
PWM_Output
N/A
3.3 v
0 v
N/A
4 mA
All other inputs
2.5 v
3.3 v
0 v
0.4 v
4 mA
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Block Diagram
Serial UART
EEPROM
Input Buffer
CPU
Transmitter
Receiver
U.FL
ADC
Force
9600 CMD/
Data
RXD
RTS
TXD
CTS
InRange PWM
PA
uP_Reset
RM024
LNA
Output Buffer
DE/RE
Integrated
Antenna
RF Switch
Figure 1: Block Diagram of RM024
Timing Specifications
Table 5: Timing Specifications
Parameter
Server/Client
Min.
Typ.
Max.
Notes
Power on to
CTS Low
5 ms
10 ms
N/A
The first boot after a FW
upgrade will require more than
the typical amount of time for
CTS to toggle Low.
EEPROM Read
800 µs
1 ms
2 ms
Measured from last byte of
command to first byte of
response: 870 µs for 1 byte 1.1
ms for 80 bytes 1.4 ms for 256
bytes
EEPROM Write
20 ms
30 ms
40 ms
Measured. EEPROM writes will
cause the radio to
resynchronize
Power on to In
Range
Client only,
server will go in
range in fewer
than 13 ms
13 ms
600 ms
1700 ms1
Maximum time assuming all
beacons are heard, RF
interference could extend the
maximum time indefinitely
Hope Period In
Range
13.19 ms
Hop Period Out
of Range
Client only
38.4 ms
Reset Pulse
250 ms
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Parameter
Server/Client
Min.
Typ.
Max.
Notes
PWM Output
Period
39.3846 µs
Restore Default
EEPROM
Command
10 ms
38 ms
Restore command also initiates
a soft reset, so monitoring CTS
is the best indication of a
completed command
Non Specific AT
Command
1 ms
10 ms
Some AT Commands could
wait indefinitely for a response
Write Flash
For FW Upgrade
Read Flash
Decrypt Image
RF Hop Frame
The RM024 hops every 13.19 ms and can be configured for two different RF data rates to provide options for
range or throughput. During each hop, the RM024 reserves a certain amount of time for overhead, such as
the synchronization beacon, internal messaging, and user data transmission. The diagrams below outline the
various transmissions that occur during a hop. These transmissions are transparent to the user sending data,
but may be useful for applications that require critical timing. User data is only transmitted during the data
slots and after the Interface Timeout or RF Packet Size criteria has been met. Data transmission only begins at
the beginning of a data slot. When configured for Full Duplex, data slot 1 is reserved for the server and data
slot 2 is shared by all clients for transmissions.
Figure 2: RF Hop Frame
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HARDWARE INTERFACE
Pin Descriptions
RXD and TXD
The RM024 accepts 3.3 VDC TTL level asynchronous serial data from the OEM Host via the RXD pin. Data is
sent from the transceiver, at 3.3 V levels, to the OEM Host via the TXD pin. Pins should be left floating or
high when not in use. Leaving the RXD tied low results in the radio transmitting garbage serial data across
the RF.
Force 9600 /Sleep Interrupt
When pulled logic Low before applying power or resetting, the transceiver’s serial interface is forced to 9600,
8-N-1 (8 data bits, No parity, 1 stop bit): regardless of actual EEPROM setting. The interface timeout is also
set to 3 ms and the RF packet size is set to the default size for the selected RF data rate. To exit, the
transceiver must be reset or power-cycled with Test pin logic high or disconnected.
When enabled in the EEPROM, 9600 Boot Option causes the 9600 pin to be ignored on cold boot (power-
up), command boot (0xCC 0xFF) and brown-out conditions. Therefore, the 9600 pin is only observed on
warm boots (reset pin toggled). This can be helpful so that brown-out conditions don’t cause the baud rate
to change if the 9600 pin happens to be low at the time. When 9600 Boot Option is disabled, the 9600 pin is
used for all boot conditions. 9600 Boot Option is enabled by default.
Force 9600 is also used to wake the radio from sleep. When the pin is taken low, the radio wakes. The
transceiver does not sleep if the pin is low when the sleep command is issued.
Note: Because this pin disables some modes of operation, it should not be permanently pulled low
during normal operation.
µP_RESET
µP_Reset provides a direct connection to the reset pin on the RM024 microprocessor and is used to force a
hard reset. For a valid reset, reset must be asserted Low for an absolute minimum of 250 ns.
Command/Data
When logic High, the transceiver interprets incoming serial data as transmit data to be sent to other
transceivers. When logic Low, the transceiver interprets incoming serial data as command data. When logic
Low, data packets from the radio are not transmitted over the RF interface, however, incoming packets from
other radios are still received. Enabling CMD/Data RX Disable in the EEPROM causes incoming RF packets to
be queued by the receiving radio while CMD/Data is low. When CMD/Data goes high, the data is sent over
the serial interface.
In_Range
The In Range pin is driven low when a client radio’s frequency hopping is synchronized with that of a server.
In Range is always driven low on a server. Following boot, In Range transitions low in approximately 12 ms on
a server. For a client the In Range takes an average of 500 ms, this time is dependent on the signal strength
of the received beacon, the presence and strength of interference and randomness of the sync function. It
can vary from 150 ms to over 1500 ms.
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GO_0/Hop_Frame
The Hop Frame indicator functionality is disabled by default and controlled by the Control 1, Bit-6 EEPROM
Setting. When enabled, this pin transitions logic Low at the start of a hop and transitions logic High at the
completion of a hop. The OEM host is not required to monitor Hop Frame.
RTS and Handshaking
With RTS mode disabled, the transceiver sends any received data to the OEM Host as soon as it is received.
However, some OEM hosts are not able to accept data from the transceiver all of the time. With RTS enabled
in EEPROM, the OEM host can prevent the transceiver from sending it data by de-asserting RTS (High). Once
RTS is re-asserted (Low), the transceiver sends packets to the OEM host as they are received.
Note: Leaving RTS de-asserted for too long can cause data loss once the transceiver’s transmit buffer
reaches capacity.
CTS Handshaking
If the transceiver buffer fills up and more bytes are sent to it before the buffer can be emptied, data loss will
occur. The transceiver prevents this loss by deasserting CTS high as the buffer fills up and asserting CTS low
as the buffer is emptied. CTS should be monitored by the host device and data flow to the radio should be
stopped when CTS is high.
DE/RE
When enabled, RS485 Data Enable uses the DE/RE pin to control the DE pin on external RS-485 circuitry.
When the transceiver has data to send to the host, it asserts DE/RE High, sends the data to the host, and then
takes DE/RE low.
PWM Output
PWM output can be configured to output on any of three pins (SMT Pins 5, 6, or 7). The PWM Output can
optionally produce a pulse width modulation for RSSI with a period of 39.3846 µS.
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THEORY OF OPERATION
Server/Client Architecture
The RM024 utilizes server-client network architecture to synchronize the frequency hopping. Each network
must have one radio configured as a server and all other radios configured as clients. When a radio is
configured as a server, it transmits a beacon containing timing and identification information at the
beginning of each hop. The beacon is never visible to the OEM host. Upon boot, radios configured as clients
enter receive mode where they are scanning the available frequencies listening for a beacon from a server in
their network. When a client detects the server’s beacon, the client synchronizes its frequency hopping to
that of the server and transition the InRange pin Low. When the server and the client are synchronized they
can begin transferring data.
Each network consists of only one server. Multiple networks can exist in the same area, provided the
networks are configured on different channels. The RM024 utilizes an intelligent Frequency Hopping
algorithm which ensures minimal interference between networks. The possible interference between
collocated networks is given by the following equation:
Maximum number of interfering bins = # of collocated servers -1
For example, with ten collocated networks, there is up to nine bins every hop cycle that are occupied by more
than one network at the same time. Although two or more networks might occupy the same hop bin at the
same time, there is truly only interference if two or more radios from alternate networks are trying to
transmit on the same bin at the same time in the same coverage area.
Adjustable RF Data Rate
The RM024’s RF data rate can be adjusted to provide a trade-off between throughput and range.
Table 6: RM024 RF Data Rate
Product Model
RF Profile
RF Data Rate
Number of Hops
Receiver Sensitivity
Throughput1
All RM024
0x00
500 kbps
43
-94 dBm
250 kbps
125 mW versions
(RM024-X125) only
0x01
280 kbps
79
-95 dBm
120 kbps
All RM024
0x03
280 kbps
43
-95 dBm
120 kbps
1. Throughput is ideal, one direction, with no retransmissions. All practical RF applications should
allow for retransmission of data due to interference or less than ideal RF conditions.
Deciding which RF data rate to choose depends on the individual application. The fast RF data rate delivers
much faster throughput, but has much less range. In addition, because the lower data rate solution uses
more hops, it is better situated for collocated networks. In firmware version 1.2-5 and above, the RF data rate
is set by the appropriate RF Profile, EEPROM Address 0x54.
A rule of thumb for RF systems is every six dB of gain doubles the effective distance. The four dB increase of
Receive Sensitivity for the lower data rate solution means it is able to transmit almost 60% further than the
higher data rate solution.
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Modes of Operation
The RM024 has three different types of interface modes:
Transparent Mode
API Mode
Command Mode
The first two modes are used to transmit data across the RF and the third mode is used to configure the
radio.
Transparent Mode
When operating in transparent mode, the RM024 can act as a direct serial cable replacement in which RF
data is forwarded over the serial interface and vice versa. In transparent mode, the radio needs to be
programmed with the MAC address of the desired recipient. The destination address can be programmed
permanently or on-the-fly.
When transparent mode is used, data is stored in the RX buffer until one of the following occurs:
The RF packet size is reached (EEPROM address 0x5A)
An Interface Timeout occurs (EEPROM address 0x58)
All parameters can be configured by entering Command Mode using either AT commands or by toggling the
Command/Data pin low on the transceiver.
Transparent mode is the default radio operation mode.
API Mode
API mode is an alternative to the default transparent operation of the RM024 and provides dynamic packet
routing and packet accounting abilities to the OEM host without requiring extensive programming by the
OEM host. API mode utilizes specific frame-based packet formats, specifying various vital parameters used to
control radio settings and packet routing on a packet-by-packet basis. The API features can be used in any
combination that suits the OEM’s application specific needs.
The RM024 has three API functions:
Send Data Complete
Receive API
Transmit API
For additional details and examples, please refer to the API Operation section of this manual.
Command Mode
Command mode is used to configure and poll for status of the transceiver. Command mode can be entered
by issuing the Enter AT Command string or by setting the CMD/Data pin low. Details of using command
mode to configure the RM024 are detailed in Configuring the RM024.
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Serial Interface Baud Rate
In order for the OEM host and a transceiver to communicate over the serial interface they must have the
same serial data rate. This value determines the baud rate used for communicating over the serial interface to
a transceiver. For a baud rate to be valid, the calculated baud rate must be within ±3% of the OEM host
baud rate.
Table 7: Baud Rate/Interference Rate
Desire Baud Rate
Baud (0X42)
Minimum Interface Timeout 1 (0X58)
230400
0x0A
0x02
1152002
0x09
0x02
57600
0x08
0x02
38400
0x07
0x02
28000
0x06
0x03
19200
0x05
0x05
14400
0x04
0x07
9600
0x03
0x10
4800
0x02
0x15
2400
0x01
0x2A
1200
0x00
0x53
Non-standard
0xE3
Use equation below
1. Interface timeout = 200 µs per increment, the EEPROM address 0x58 is ignored if Auto Config is
enabled. To use a non-standard Interface Timeout, disable Auto Config.
2. Default baud rate.
For baud rates other than those shown in Table 7, the following equations can be used:
(256 + BAUD_M * (2BAUD_E) * FREQUENCY
Baud Rate = ___________________________________
228
Where:
FREQUENCY = 26 MHz
BAUD_M = EEPROM Address 0x43
BAUD_E = EEPROM Address 0x44
100000
Minimum Interface Timeout = _______
Baud Rate
Tips:
The RM024 supports a majority of standard as well as non-standard baud rates. To select a standard
baud rate, use the value shown for EEPROM address 0x42 in Table 7. To enable a non-standard baud
rate, program EEPROM address 0x42 (Custom Baud Enable) to 0xE3 and then use the equation above
to solve for BAUD_M and BAUD_E.
Adjusting the serial interface baud rate does not affect the RF data rate.
Radio can accept serial combinations (number of bits, parity, number of stop bits) of 8-N-1, 7-N-2, 7-1-
1, by default. Modes of 8-1-1, 8-N-2, 7-1-2 are acceptable with 9-bit mode enabled.
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CONN-GUIDE-RAMP24-0413
Interface Timeout/RF Packet Size
Interface Timeout
Interface timeout specifies a maximum byte gap between consecutive bytes. When that byte gap is exceeded,
the bytes in the transmit buffer are processed as a complete packet. Interface timeout (EEPROM address
0x58), in conjunction with the RF packet size, determines when a buffer of data is sent out over the RF as a
complete RF packet, based on whichever condition occurs first. Interface timeout is adjustable in 200 us
increments and should be equal to or greater than two full bytes times. The minimum interface timeout is
0x02.
The radio uses the default interface timeout for a given baud rate if Auto Config is enabled, despite what is
written in the interface timeout address. To use a non-standard interface timeout, the OEM needs to disable
Auto Config.
RF Packet Size
RF packet size is used in conjunction with interface timeout to determine when to delineate incoming data as
an entire packet based on whichever condition is met first. When the transceiver receives the number of
bytes specified by RF packet size (EEPROM address 0x5A) without experiencing a byte gap equal to interface
timeout, that block of data is processed as a complete packet. Every packet the transceiver sends over the RF
contains extra header bytes not counted in the RF packet size. Therefore, it is much more efficient to send a
few large packets than to send many short packets. The maximum RF packet size is 239 bytes, or 0xEF, at
500 kbps RF data rate and 96 bytes, or 0x60, at 280 kbps RF data rate.
The RF packet size in address 0x5A will not be used if Auto Config (Address 0x56, bit 0) is enabled. The
default for the RF data rate will be used instead. The RF packet size should not be set to less than 0x07, to
ensure AT commands can still be issued.
RF packet size is also used by the radio to determine the number of data slots per hop. In order to efficiently
transmit data across the RF the radio automatically adds more data slots to the hop to correspond to a
smaller RF packet size. The number of slots per hop is given in the table below.
RF Data Rate
RF Packet Size
Number of Data Slots
280 kbps
0x01 –0x09
4 slots
280 kbps
0x0A –0x25
3 slots
280 kbps
0x26 –0x60
2 slots
500 kbps
0x01 –0x0C
6 slots
500 kbps
0x0D –0x25
5 slots
500 kbps
0x026 –0x47
4 slots
500 kbps
0x48 –0x7D
3 slots
500 kbps
0x7E –0xEF
2 slots
Tips:
The more slots per hop, the less likely that retries will occur on a new frequency which may reduce the
effectiveness of the module as a Frequency Hopping radio.
Idle current consumption increases as more slots are added.
You must use the same number of slots for every radio on the network.
Full duplex only reserves the first slot for the server. If there are six slots, the first slot is reserved for the
server to transmit and the remainder is shared by the clients.
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RM024 User Manual
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CONN-GUIDE-RAMP24-0413
RS-485 Data Enable
The timing of the DE-RE pin varies depending on the selected interface baud rate. Prior to firmware v2.2,
these parameters are set automatically if Auto Config is enabled. If Auto Config is disabled, these values must
be set correctly, even if RS-485 Data Enable is not being used. In v2.2 and beyond these parameters are not
controlled by Auto Config, but instead by Address 0x57, bit 5.
The values to set are:
485_Delay_H: Address 0x49
485_Delay_M: Address 0x4A
485_Delay_L: Address 0x4B
To set them, use the following equation (round the result up):
Address 0x49 and 0x4A: 485H/M = 8.125 MHz / (81*Baud_Rate), quotient only
Address 0x4B: 485L = (8.125MHz / Baud_Rate) mod 81
So for 19,200 you should calculate 00 05 12.
Flow Control
Although flow control is not required for transceiver operation, it is recommended to achieve optimum
system performance and to avoid overrunning the RM024’s serial buffers. The RM024 uses separate buffers
for incoming and outgoing data.
RXD Data Buffer and CTS
As data is sent from the OEM host to the radio over the serial interface, it is stored in the RM024’s buffer
until the radio is ready to transmit the data packet. The radio waits to transmit the data until one of the
following conditions occur (whichever occurs first):
The RF packet size is reached (EEPROM address 0x5A)
An interface timeout occurs (EEPROM address 0x58)
The data continues to be stored in the buffer until the radio receives an RF Acknowledgement (ACK) from the
receiving radio (addressed mode), or all transmit retries/broadcast attempts are used. Once an ACK has been
received or all retries/attempts are exhausted, the current data packet is removed from the buffer and the
radio begins processing the next data packet in the buffer.
To prevent the radio’s RXD buffer from being overrun, we strongly recommend that the OEM host monitors
the radio’s CTS output. When the number of bytes in the RXD buffer reaches the value specified by CTS_ON
(EEPROM address 0x5C - 0x5D), the radio de-asserts (high) CTS to signal to the OEM host to stop sending
data over the serial interface. CTS is re-asserted after the number of bytes in the RXD buffer is reduced to the
value specified by CTS_OFF (EEPROM addresses 0x5E- 0x5F); signaling to the OEM host that it may resume
sending data to the transceiver.
Note: We recommend that the OEM host stop all data transmission to the radio while CTS is de-asserted
(high); otherwise potential data loss may occur.
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CONN-GUIDE-RAMP24-0413
TXD Data Buffer and RTS
As data to be forwarded to the OEM Host accumulates, it is stored in the RM024’s outgoing buffer until the
radio is ready to begin sending the data to the OEM Host. Once the data packet has been sent to the Host
over the serial interface, it will be removed from the buffer and the radio will begin processing the next data
packet in the buffer. With RTS Mode disabled, the transceiver will send any data to the OEM Host as soon as
it has data to send. However, some OEM Hosts are not able to accept data from the transceiver all of the
time. With RTS Mode Enabled, the OEM Host can prevent the transceiver from sending it data by de-asserting
RTS (High), causing the transceiver to store the data in its buffer. Upon asserting RTS up to two additional
bytes can be received over the serial interface before the flow is stopped. Once RTS is re-asserted (Low), the
transceiver will continue sending data to the OEM Host, beginning with any data stored in its buffer.
Note: Leaving RTS de-asserted for too long can cause data loss once the radio’s TXD buffer reaches
capacity.
Tip:
Can I implement a design using just TXD, RXD, and GND (three-wire interface)?
Yes. However, it is strongly recommended that your hardware monitor the CTS pin of the radio. CTS is
taken High by the radio when its interface buffer is getting full. Your hardware should stop sending at
this point to avoid a buffer overrun (and subsequent loss of data). You can perform a successful design
without monitoring CTS. However, you need to take into account the amount of latency the radio adds
to the system, any additional latency caused by retries, how often you send data, non-delivery network
timeouts, and interface data rate. Laird Technologies can assist in determining whether CTS is required
for your application.
Radio Configurations
Antenna Switch (EEPROM 0xC1, bit 5)
Selects either integrated chip antenna or U.FL connector for external antenna
Note: On RM024 –C units with no integrated antenna, the RF switch is still active and it is possible,
though not advised to switch to the integrated antenna option, even though there is no antenna
connected. RF performance in this configuration would be degraded. See Antenna Select Override
for additional options.
Antenna Select Override (EEPROM 0x5B)
Disables the antenna switch on –C products causing the firmware to ignore the setting in Antenna Switch
and use the U.FL port automatically.
Note: Product ID’s containing an “M” (RM024-S125-M-01, RM024-P125-M-01, RM024-S50-M-01 and
RM024-P50-M-01) have both antennas installed (chip antenna and u.FL). However, products
containing a “C” (RM024-S125-C-01, RM024-P125-C-01, RM024-S50-C-01 and RM024-P50-C-
01) only have the u.FL installed. Therefore, selecting chip antenna on a “C” product results in no
RF link. This feature does not work in FW v1.3-0 on 50 mW radios (RM024-x50-C-01).
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RM024 User Manual
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CONN-GUIDE-RAMP24-0413
Auto Channel (EEPROM 0x56, bit 3)
To allow for more flexible network configurations, Auto Channel can be enabled in clients to allow them to
automatically synchronize with the first server they detect, regardless of channel number.
Note: A client with Auto Channel only synchronizes with a server that has a matching System ID.
Auto Config (EEPROM 0x56 bit 0)
The optimal settings for interface timeout and RF packet size vary according to the selected RF profile and
interface baud rate. Enabling Auto Config bypasses the value for these variables stored in EEPROM and uses
predetermined values that have been optimized for the given mode. When Auto Config is disabled, these
values must be programmed in the transceiver EEPROM.
Auto Destination (EEPROM 0x56, bit 4)
To simplify EEPROM programming, Auto Destination can be enabled in the radio which allows the radio to
automatically set its destination to the address of the radio from which it last received a successful
transmission from (beacon or data packet).
Auto Destination on Beacons Only (Address 0x56, bit 7)
When Auto Destination is enabled, the client radio addresses itself to the source of any received packet,
including beacons from the server and any addressed or broadcast packets it receives. For point to multipoint
networks where the client is intended to only communicate back to the server, this could cause the client to
inadvertently become addressed to another client. By enabling Auto Destination on Beacons Only, the client
only addresses itself upon reception of beacons, therefore it only addresses itself to the server. Auto
Destination on Beacons Only is only functional when Auto Destination is also enabled.
Auto System ID (EEPROM 45, bit 4)
When enabled, Auto System ID allows a client to attach to any server on the same RF channel, regardless of
the System ID on the server or the client.
Beacon Skip (EEPROM 0x6F)
When set, the transceiver will send (server) or listen (client) for a beacon on hops spaced by the Beacon Skip
number. On a client, once the Beacon Skip count is reached the client will listen every hop until it successfully
hears a beacon. It will then wait a number of hops specified by the Beacon Refresh before listening again.
Enabling this will allow the transceiver to conserve power by disabling its RF circuitry during the beacon time.
Enabling this on the server causes substantially longer sync times on the clients.
Broadcast (EEPROM 0xC1, bit 7)
In Broadcast mode, the transceiver transmits the packet to all transceivers with the same Channel Number
and System ID settings. There is no RF acknowledgement sent from the recipient(s) back to the transmitter,
therefore the packet is sent out the number of times specified by Broadcast Attempts.
Broadcast Attempts (EEPROM 0x4D)
When transmitting broadcast packets, the RF packet is broadcast out to all eligible receivers on the network.
Broadcast Attempts is used to increase the odds of successful delivery to the intended receivers. Transparent
to the OEM host, the transmitter sends the RF packet to the receivers. If a receiver detects a packet error, it
throws out the packet. This continues until the transmitter exhausts all of its attempts. Once the receiver
successfully receives the packet, it sends the packet to the OEM host. It throws out any duplicates caused by
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RM024 User Manual
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CONN-GUIDE-RAMP24-0413
further broadcast attempts. The received packet is only sent to the OEM host if it is received free of errors.
Because broadcast packets have no RF acknowledgement, each packet is transmitted the number of times
specified by Broadcast Attempts. This makes for inefficient use of the available bandwidth; therefore, it is
recommended that Broadcast Attempts be set as low as possible and that broadcast packets be limited in
use.
Note: Setting to 0 is equal to 256.
Cyclic Sleep (EEPROM 0x61, bit 0)
Causes the radio to sleep for a programmable period of time and wake for a programmer period of time. The
radio can be awakened from sleep before its sleep cycle completes using the Force 9600 pin. Additionally,
the wake time is an inactivity counter. Therefore, the device stays awake indefinitely as long as the device
continues sending packets over the RF interface.
Destination Address (EEPROM 0x79-0x75)
The Destination Address is simply the MAC (IEEE) address of the intended receiver on the network. In
Addressed mode, the RF packet is sent out to the intended receiver designated by the destination address.
Only the four LSBs (Least Significant Bytes) of the destination address are actually used for packet delivery.
This field is ignored if Broadcast mode, Auto Destination, or Transmit API is enabled.
Disable Status Bin (EEPROM 0xC1, bit 4)
When set, disables the reception on the status slot of the bin. The result is that the bin analyzer and remote
I/O functionality is disabled on the radio with the benefit of saving approximately 1 mA average current
consumption.
Discard Framing Error Packets (EEPROM 0x57, bit 7)
When set, the radio checks for a framing error in the UART buffer before processing incoming data. If an
error is detected on any of the bytes in the buffer, the entire buffer is discarded.
Full Duplex (EEPROM 0x56, bit 1)
In Half Duplex mode, the transceiver sends a packet out over the RF immediately. This can cause packets sent
at the same time by a server and a client to collide with each other over the RF. To prevent this, Full Duplex
mode can be enabled. This mode reserves a transmit “slot” for the server. If the server does not have any
data to transmit, clients are permitted to transmit during that time. If the server does have data to send,
clients will not be permitted to transmit during that slot. Likewise, the server will not be able to transmit
during a client slot. Though the RF hardware is still technically half duplex, it makes the transceiver seem full
duplex. This can cause overall throughputs to be cut in half.
Note: All transceivers on the same network must have the same setting for Full Duplex.
Hop Packet Delineation (EEPROM 0x57, bit 6)
When enabled, in addition to using RF packet size and interface timeout as criteria for processing incoming
data, the radio also delineates packets up to once per hop once a minimum of six characters has been
received over the serial port.
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RM024 User Manual
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CONN-GUIDE-RAMP24-0413
Legacy RSSI (EEPROM 0x45, bit 2)
RSSI (Received Signal Strength Indicator) is a measure of how well the receiving radio is able to hear the
transmitting radio. By default, RSSI is reported in 2’s complement format; therefore, values range from 0x80 -
0x7F. Many preceding products have, instead, reported RSSI in the range of 0x00 - 0xFF. Legacy RSSI causes
0x80 to be added to the RSSI result prior to reporting it to the host.
Max Power (EEPROM 0x63)
The transceiver has an adjustable RF output power. Power can be adjusted dynamically to optimize
communications reliability and conserve power. Each increment represents a 3 dBm 50% decrease in power.
The radios have a maximum input RF level of 0 dBm. When operated very close together at full power, the
radio’s receiver can saturate and no transmissions are possible. If the distance between the transmitter and
receiver is very short (generally less than 2 ft (.6 m) with 2.5 dBi antennas), the maximum power should be
reduced.
Mode (Server/Client) (EEPROM 0x41)
The server controls the frequency hop timing by sending out regular beacons (transparent to the transceiver
host) which contain system timing information. This timing information synchronizes the client radio
frequency hopping to the server. Each network should consist of only one server.
Nine Bit Mode (EEPROM 0x57, bit 1)
With Nine Bit mode disabled, the transceiver communicates over the asynchronous serial interface in 8-N-1
format (8 data bits, No parity, 1 stop bit). Some systems require a parity or 9th data bit. Enabling Nine Bit
mode causes the transceiver to communicate using 8-1-1 format (8 data bits, 1 parity bit, 1 stop bit). In this
mode, the transceiver does not validate the parity bit but simply transmits it over the RF. This is useful as
some systems use the ninth bit as an extra data bit and not just a parity bit. However, because the ninth bit is
transmitted over the RF, enabling Nine Bit mode cuts the transceiver interface buffer size by 1/9 and reduces
the RF bandwidth by the same ratio.
Random Backoff (EEPROM 0xC3)
The transceivers utilize a retry protocol with Random Backoff and a programmable back-off seed. Therefore,
in the event an acknowledgement is not received, the transceiver backs off and retries the packet. For
example, when two transceivers collide with each other (transmitting packets at the same time), each
transceiver chooses a random number of packet times that it will wait before retrying the packet. Ideally, they
each choose a different number and are successful in the next transmission. A good rule of thumb is to set
Random Backoff to a number slightly larger than the maximum number of transceivers that would be
expected to be transmitting at the same time. When set to transmit broadcast packets, where there is no
acknowledgment available, the Random Backoff value is used for all subsequent attempts.
Range Refresh (EEPROM 0x3D)
Range refresh specifies the maximum amount of time a transceiver reports In Range without having heard a
server’s beacon. It is adjustable in hop periods. Do not set to 0.
Remote I/O Mode (Address 0x57, bit 3)
Remote I/O mode allows GPIOs on two radios to be joined together so their states are reflected on the other
radio. Enabling Remote I/O mode allows the local radio to transmit its GPIO states whenever there is a
change. The states are transmitted to the radio specified by the Destination Address (or as a broadcast if
Broadcast mode is enabled). State information is only transmitted when there is a change on one of the
enabled Digital Inputs. The states are retransmitted up to the number of specified Utility Retries (Address
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