Campbell Scientific RF401-series and RF430-series Spread Spectrum Data Radios/Modems - Manual (Page 124)

Appendix M. PakBus Networking Details
M.8 Optimization
Since response speed is always important, you should use the fastest IO mode
available. Specifically the fastest IO mode is CSDC for the datalogger
interface and 38.4k for the RS-232 interface. Another reason to use the fastest
IO mode is that the RF401 buffers the entire PakBus packet before sending it to
the radio module (the RF400 would just start streaming it to the radio
immediately), and therefore introduces a delay.
The RF401 or RF430 can handle full size (1000 byte) PakBus packets.
However, decreasing the size of the PakBus packets to ~240 bytes will provide
better throughput when there is heavy RF traffic or the collection of a lot of
data. Large PakBus packets are spread across multiple RF packets, which
could cause another RF packet to be interleaved, leading to the corruption of
the larger PakBus packet. Essentially, the PakBus packet is fragmented, and
received out of order. No mechanism exists that reorders the individual RF
packets. The PakBus size is an adjustable setting in our PakBus dataloggers
and in the LoggerNet server.
M.9 Idiosyncrasies
As mentioned under Net and Radio Address Settings, only four Net Addresses
are available (0-3). Combining the seven unique hop sequences with the four
Net Addresses provides a total of 28 (4x7) unique combinations for networks.
This is far fewer combinations than available for the RF400 radios, increasing
the likelihood of RF401 networks that merge unexpectedly.
Also, there is potential for interference from RF400 radios. RF400 radios with
Net Addresses of 28, 44, 52, and 56 will interfere with and be interfered by
RF401 or RF430 radios with Net Addresses of 0, 1, 2, and 3 respectively. The
RF400 Net Address of 60 will interfere with ALL RF401 Net Addresses.
Therefore if RF400 radios and RF401/RF430 radios will be in the same RF
proximity, do not use 28, 44, 52, 56, or 60 for the RF400s Net Addresses.
A positive side effect of the RF PakBus protocol is that the node that is
attached to the RF401/RF430 (datalogger or server) will only receive PakBus
packets that are addressed to it or globally addressed packets. The rest of the
packets are filtered out by the radio. This will reduce the overall current
consumption of the datalogger.
When the Protocol is set to one of the PakBus protocols, the radio “discovers”
the PakBus address of the attached node by looking at the header of any
outbound PakBus packet. If no outbound packet (could be a beacon, or Hello,
or anything else) is sent for 6 minutes, the RF401 will send a Hello Request
packet to the attached node. If the protocol is set to PakBus Aware, these
Hello Request packets are sent alternately from PakBus node 4088 and 4089.
That is, the radio temporarily “assumes” the PakBus identity of 4088 or 4089
until it finds the PakBus address of the attached device. The reason for
alternating between these two addresses is in case the attached node has the
same address.
M-4