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DNT90 Integration Guide - 05/10/12
all configuration commands, replies, event messages and announce messages, a 20 byte minimum slot
size is required.
The
NumSlots
and the
MsgsPerHop
parameters both affect the number of messages that can be sent on
each hop. The distinction between these parameters is as follows:
- The
NumSlots
parameter controls the maximum number of
individual children
that can send
messages to a parent on each hop.
- The
MsgsPerHop
parameter controls the
maximum number of messages a parent or child
can
send on each hop.
The
NumSlots
parameter is configurable
only
for the base. The base then communicates the
NumSlots
value to all other radios in its system. The
NumSlots
parameter can be set to one for a point-to-point sys-
tem, as there is only one child radio. The
NumSlots
parameter can be set to allow up to eight children to
send messages to their parent during a hop. As discussed above, the hop duration must be increased as
the number of slots are increased to achieve a specific RSS. The default
NumSlots
parameter value of
three is suitable for many applications.
De facto
TDMA operation (guaranteed bandwidth) can be implemented for up to 8 remotes by setting the
SlotLease
parameter to a value greater than any gaps in data being sent to a remote by its local host.
This will insure that the base keeps each remote’s slot reserved for it even when there is a gap in the da-
ta.
The
MsgsPerHop
parameter is configurable
for each
DNT90 in a system. This parameter is usually set to
a high value in the base and the routers, allowing traffic between a parent and multiple children on each
hop. The
MsgsPerHop
parameter has little effect in remotes except when a remote needs to send multi-
ple peer-to-peer messages during a hop. To support sending multiple messages on each hop, the BSS
and RSS must be sized accordingly, requiring a longer hop duration. Note that the messages must be
protocol messages and all messages to be sent on a single hop must be in the module before the module
begins to transmit.
5.0 DNT90 Application Interface Configuration
DNT90 modules include a comprehensive set of application interfaces and related options that support a
wide range of applications including wireless RS232/485 cable replacements, wireless sensor networks,
wireless alarm systems and industrial remote control applications. Recommended configuration steps for
each application interface are discussed in Sections 5.1 through 5.7 below.
5.1 Configuring the Serial Port
The default serial port configuration is 9.6 kbps, 8-bit data, no parity and 1 stop bit.
1. Configure the serial data rate as required from 1.2 to 250 kbps by setting the
SerialRate
parameter in Bank 3.
2. Configure the parity and number of stop bits by setting the
SerialParams
parameter in Bank 3.
3. Enable/disable serial port hardware flow control as required by setting the
GpioAlt
parameter in
Bank 6. Hardware flow control is disabled by default, but is recommended when operating at
higher baud rates and/or sending large blocks of data.
