Insertion by Dennis; reviewed:
- DRC 0 errors / 0 unconnected / 0 schematic parity
- R32-R35 sit in-line between the termination cluster and D4/D5, each
aligned to its own line row; MDI_* stubs only 1.45-1.48mm, no new
vias, all pair copper at the ETH_DP 0.2mm width
- Pair skew after insertion: TX 0.66mm, RX 1.81mm - both far inside
the 100BASE-TX budget
- C20/C21 placed against J2's pin column, about as close as the In1
plane void allows while keeping short GND vias
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
SP1 DO/DI naming is console-perspective (verified against SD Gecko and
SD2SP2 wiring): pin 6 DO = GC data out = adapter MOSI input, pin 9 DI =
GC data in = adapter MISO output. The design doc's SP1 table had the
roles reversed and the schematic followed it, putting the FPGA's MISO
driver on the GC-driven DO line (bus contention).
Fix keeps all PCB routing identical:
- Swap net names EXI_MOSI(_RAW) <-> EXI_MISO(_RAW) across exi/Fpga/root
sheets and the PCB (also renames the D2 PUSB3AB6 channel assignments).
- Swap R21 (22R) <-> R25 (33R) identities between the two footprint
positions so 33R stays on the FPGA-driven MISO line, 22R on the MOSI
input.
- Correct the SP1 pin table + MISO-tristate note in
docs/gc_bba_fpga_design.md (root cause).
Resulting board pin map (for the future board PCF): EXI_MOSI = FPGA
pin 4 (IOB_8a, input), EXI_MISO = pin 3 (IOB_9b, output).
Verified: ERC 0, DRC 0 errors with schematic parity 0, netlist shows
J3.6(DO)->R21->pin 4 and J3.9(DI)->R25->pin 3.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Roflin
Dennis Brentjes