The dip-switch (S2) routes to FPGA pins J16, K16, K15, and L14 (see PCB silkscreen). With generic designs that dip-switch has the following uses:
{| class="wikitable"
!J16
!Input Clock Source
|-
|1
|ChipWhisperer HS-IO
|-
|0 (Default)
|PLL1
|}
{| class="wikitable"
!K16
!ChipWhisperer HS-Out
|-
|1 (Default)
|Enabled (clock)
|-
|0
|Disabled
|}
See the example design documentation for more details.