Infineon AIROC CYW43012 Manual page 19

Low-power system design with AIROC™ Wi-Fi & Bluetooth® combo
chip and PSoC™ 6 MCU
WLAN power optimization techniques
You want to keep the host processor involvement to a minimum by filtering and passing only the wanted
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traffic to it.
Filters can be configured to be active either when the host processor is active or asleep (or both). Multiple filters
may be configured to operate simultaneously. One set can be functioning while awake and a separate set can
function while sleeping and can be used to wake the host. In addition, filters can be configured to either discard
or keep (send to host). When configured to discard, only the specified packets are discarded, while any others
not specifically filtered are passed to the host. Conversely, when configured to keep packets, only the specified
packets are passed to the host, and the rest are discarded.
A typical model would be to use only 'keep' filters, where the application is aware of all the types of packets it
needs to process. In other words, use 'keep' filters to specify the complete list of packet types the host is
interested in and discard the rest. This is preferred as it is much simpler to list the packets the host wants to
receive versus creating a complete list of packets it does not want. When using keep filters, care must be taken
to allow enough packets through for networking protocols to work properly.
For example, while awake, the processor must be able to join a network, get a DHCP address, run ARP, and
possibly share network keys. Not creating enough keep filters to allow these types of packets through will
prevent the host from even joining the network. A reasonable minimal set of keeping filters should include:
ARP (allow ARP packets)
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IEEE 802.1X (allow security packets)
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DHCP (UDP port 68)
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DNS (UDP port 53)
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There is no minimum set of filters required when enabling discard filters. However, it should be noted that all
the filter types in the offload must be either keep or discard and not a mix of both. This is because the
complementary nature of the keep and discard filters will result in unexpected behavior.
Three types of packet filters are supported in AIROC™ CYW43012 Wi-Fi & Bluetooth® combo chip based on a
standard network stack as seen in
packet filters.
Figure 7 Packet filters
Application note
Figure 7, which shows the relationships between stack layers, protocols, and
19 002-27910 Rev. *C
2023-05-29