A sheet-by-sheet tour of the KrIO schematic, showing what each part of the design does and which signals cross between them.
Updated 2026-09-01
The schematic is split into six sheets, and each one owns a job that the others do not
touch. This page walks through them in the order that makes sense when you are trying to
understand the board rather than build it, starting with the module everything else exists
to support.
Every number below is read out of the KiCad project when the site is built, so the part
counts and the signal names are the ones actually in the design. If a sheet gains a pin,
this page gains it too.
Ethernet A
A DP83867 gigabit PHY on RGMII, with its magnetics and jack. The sheet is instantiated twice, once per port.
ethernet.kicad_sch · 51 parts placed · 25 C, 14 R, 9 U, 2 J
Signals crossing this sheet boundary
GTX_CLKinput
MDCinput
MDIObidirectional
RX_CLKoutput
RX_CTRLoutput
RX_D[0..3]output
TX_CTRLinput
TX_D[0..3]input
n_RSTinput
Power
The whole supply tree from the 12 V input. Separate regulators feed the processor system and the programmable logic, so a fault in your front end cannot take the processor down with it.
power.kicad_sch · 34 parts placed · 15 C, 7 R, 6 U, 2 J
No hierarchical pins. Everything this sheet connects to is a global net.
Kria K26
The system-on-module and its two Samtec connectors. Everything the K26 needs to boot lives here, and the banks it exposes are routed straight out to the other sheets.
JTAG and the serial console, which are the two ways to reach a board that will not boot.
debug.kicad_sch · 31 parts placed · 10 U, 6 J, 6 R, 5 D
Signals crossing this sheet boundary
JTAG_TCK_C2Moutput
JTAG_TDI_C2Moutput
JTAG_TDO_M2Cinput
JTAG_TMS_C2Moutput
UART_RXoutput
UART_TXinput
~{PS_SRST_C2M}output
Ethernet B
The second instance of the same PHY sheet. Its MDIO lives on the first port's bus, which is why firmware finds both PHYs through one interface.
ethernet.kicad_sch · 51 parts placed · 25 C, 14 R, 9 U, 2 J
Signals crossing this sheet boundary
GTX_CLKinput
MDCinput
MDIObidirectional
RX_CLKoutput
RX_CTRLoutput
RX_D[0..3]output
TX_CTRLinput
TX_D[0..3]input
n_RSTinput
Board-to-Board I/O
The Samtec HSEC8 card edge that a front end plugs into. This is the boundary between what KrIO provides and what you build.
board-to-board_io.kicad_sch · 22 parts placed · 11 C, 5 R, 4 J, 2 U
Signals crossing this sheet boundary
SCLinput
SDAbidirectional
Reading the signal lists
The signals shown for each sheet are its hierarchical pins, which are the only
connections that cross a sheet boundary by name. A net that appears on one sheet and
nowhere else does not show up here, and neither does anything on a global label such as a
power rail. That makes the lists a good map of how the sheets talk to each other, and a
poor map of everything on any one of them.
Directions are given from the point of view of the sheet you have open. RX_CLK is an
output on an Ethernet sheet because the PHY drives it, and the same net is an input
where the K26 receives it.
Where to go next
The card edge on the Board-to-Board I/O sheet is specified pin by pin on the
connector specification. What the board does with all of this once it is
powered is in board bring-up, and the parts themselves are in the
bill of materials.