RC11xx(HP)-TM
RC25xx(HP)-TM
RC17xx(HP)-TM
2016 Radiocrafts AS
RC11xx(HP)/25xx(HP)/17xx(HP)-TM Data Sheet rev. 1.48 Page 30 of 86
2016 Tiny Mesh AS
Radiocrafts
Embedded Wireless Solutions
Practical Use of Packet Header Data
The header section is identically formatted for all Tinymesh
TM
data packets. The header section contains
valuable information for network quality analysis and data validation in a host system.
The four-byte
SYSTEM ID
uniquely identifies the network that originated the message, and may be used
as an identifier in host systems that handle multiple Tinymesh™ networks.
The
UNIQUE_ID
is unique address identifier of the device that originated the message, and an important
identifier in a host system database.
The
ORIGIN RSSI
is the RF signal strength of the first link in the hop path for the message, and is an
indication of the quality of the first link. A high value, approaching the minimum level for reliable
connection indicates poor connection, and may be an indication of poor connectivity with possibility for
unreliable connection. An RSSI value above 190 is regarded as potentially too low for stable and reliable
connection. The
RSSI ACCEPTANCE LEVEL
parameter in Configuration Memory determines the highest
allowable link RSSI for establishing a new connection.
ORIGIN NETWORK LEVEL
indicates the network hop level of the originating device at the time when the
message was dispatched. As an example, if
ORIGIN NETWORK LEVEL
is 3, it indicates the packet will
hop three times from the originating node, before reaching the Gateway. As a Tinymesh
TM
network
inherently is a dynamical network that continuously adapts to changing RF conditions, it is possible that
the packet may require more or less than the anticipated number of hops before reaching the Gateway.
The actual number of hops travelled by the packet is indicated by the
HOP COUNTER
value that will
increase by one each time the message is passed from one node to another.
The
MESSAGE COUNTER
is a unique, 16-bit number maintained by the originating node. Every message
received by a host system may be uniquely identified by a combination of the
SYSTEM ID
,
ORIGIN ID
and
MESSAGE COUNTER
.
Note that the
MESSAGE COUNTER
is reset to zero after 64k packets, or after a device Reset. In practical
implementations, it may be assumed that a new numbering sequence starts every time a
DEVICE RESET
message is received from the device. Reset messages will be generated after Power On, after a
FORCE
ROUTER RESET
Command or after execution of a Device
SET CONFIGURATION
C
ommand.
The
LATENCY COUNTER
is a 16-bit timer that is reset to zero when the packet is created, and
maintained throughout the transportation chain until the message is delivered from the Gateway Device
to the external host. The timer is updated at 10ms or 2560ms intervals, selectable by the
MAX PACKET
LATENCY TIME BASE
parameter.
The timer will stop counting after reaching the maximum value. The message transportation delay is a
good indicator of network reliability, and may be used in time critical implementations, to recreate an
accurate time stamp for an event. Typical transportation delays in systems using default configuration
settings may be expected to be less than 100ms per network hop.
Device and Network Status Interrogation
The Tinymesh
TM
protocol stack supports several optional commands for system and device status
interrogation.
Automatic, time generated status messages may be generated by setting the
IMA TIME
parameter in
Configuration Memory. For details, see
AUTOMATIC STATUS REPORTING
.
The
GET STATUS
,
GET DID STATUS
,
and
GET NID
commands all return similarly formatted status
messages with a payload portion containing the status of all input parameters: Analogue, Digital,
Temperature and Supply Voltage.
The
GET STATUS
command returns a
STATUS MESSAGE (IMA)
event message, and may also be
activated on an automatic time base by setting the
IMA TIME
parameter in Configuration Memory. The
contents of the
MESSAGE DATA MSB
,
MESSAGE DATA LSB
and
ADDRESS(ID) DATA
packet fields is
configurable through the
IMA MESSAGE DATA FIELD CONTENTS
and the
IMA MESSAGE ADDRESS FIELD
CONTENTS
parameters.
