rebbarb/hardware/re-bba-rb/REVIEW.md

# re-bba-rb hardware review — coverage record

**Purpose of this file:** a complete log of *what has been reviewed and how*, so
a future session/agent does not re-do (or re-litigate) this work. Open action
items live in [TODO.md](TODO.md); this file records **coverage and verdicts**,
including everything that was checked and found *correct*.

**Maintenance rule (binding):** whenever a reviewed circuit is changed, or a new
review/verification is performed, update the relevant section here in the same
commit. If you change something listed as "verified correct", its entry here
must be re-verified or marked stale. TODO.md tracks *what to do*; REVIEW.md
tracks *what has been established*.

Review window: 2026-07-17 … 2026-07-18. Reviewed by Claude (sessions with
Dennis), commits `4704dfb…d0426b3`. Verification tooling: `kicad-cli` 10.0.4
netlist/ERC/DRC/BOM exports, ad-hoc netlist parsers (pins.py/nets.py — parse the
kicadxml netlist into per-component pin→net tables; recreate trivially), PDF
datasheet extraction, WebSearch/WebFetch for parts and reference designs.

---

## 1. Sources reviewed against

| Source | Where | Used for |
|---|---|---|
| TPS562201, TPS2116, TPS22810, AP2112K, FT2232H, 93LC46B, USBLC6-2SC6, W5100S, iCE40UP5K, W25Q32JV, MC-711-H72, PUSB3AB6 datasheets | `datasheets/` (restored from LFS; TPS22810 + PUSB3AB6 added from web) | pin functions, abs max, app circuits |
| WIZnet **W5100S reference schematic** V1.1.0 (signal.com.tr mirror) | fetched, read as image | entire MDI/magnetics section, notes 1–7 |
| SD Gecko wiring table (gc-forever wiki), SD2SP2-Pro schematic (github), SP1ETH (github), ETH2GC (github), webhdx IDE-EXI v2 thread (gc-forever t=4843) | fetched | SP1 DO/DI direction, 12 V rail viability |
| iceprog source (`YosysHQ/icestorm/iceprog/iceprog.c`) | fetched | FTDI pin convention |
| JLCPCB/LCSC part pages | fetched per part | every C-number claimed below |

## 2. Power sheet (`Power.kicad_sch`) — FULLY REVIEWED, PASS

- **TPS562201 (U3, 12V→GC_3V3 buck)**: EN tied to 12 V **checked against abs
  max — legal (VIN/EN max 19 V)**. VFB ref 0.768 V; 33k/10k divider → 3.30 V,
  matches DS Table 7-2 (33.2k/10k). L1 3.3 µH = recommended typ; 2×22 µF out
  within 20–68 µF window; VBST 100 nF pin-to-SW; input 2×10 µF+100 nF. All per
  datasheet. Do not re-flag EN-at-12V.
- **TPS2116 (U2, GC/USB 3V3 mux)**: MODE tied to VIN1 = **priority mode**
  (checked truth table); ST = open-drain "low when VIN1 not used" → GC_ON high
  on GC power, R5 10k pull-up to 3V3 — polarity **correct** for U12-EN +
  FPGA-GC_ON use. USB-only fallback verified via truth table (MODE≤0.35 V row).
  PR1 divider was marginal (1.10 V vs VREF 1.0±8 %) → **fixed: R3=150k**
  (switchover 2.30–2.70 V). Abs max (6 V) fine.
- **AP2112K-1.2 (U1) / AP2112K-3.3 (U4)**: 1 µF X5R in/out present (DS
  requirement), 600 mA rating vs load fine, dropout headroom checked (1.2 V
  version has 1.0–1.3 V dropout — OK from 3.3 V), EN=VIN OK.
- **TPS22810 (U12, ETH_3V3 switch)**: EN never floats (GC_ON has R5 pull-up);
  QOD floating = valid config; **CT floating deliberately accepted** — DS
  Table 2: rise ~98 µs at VIN=3.3 V even with CT=0 → ~0.5 A inrush into
  ~15 µF; a CT cap changes nothing at 3.3 V. Closed — do not re-open.
- **12 V input**: D3 SMAJ12A orientation/standoff correct; C65 100 µF is a
  **25 V SMD electrolytic** (Lelon VZH101M1ETR-0607 — not THT, assembly OK);
  C3/C4 25 V, C6 50 V — ratings verified in BOM.
- **12 V rail viability**: verified against webhdx IDE-EXI v2 / M.2 Loader
  ("3.3V@2A from 12V rail", gc-forever t=4843) — a shipping SP1 product runs
  the same architecture at higher load. Only remaining bench check: inrush
  into C65 at GC power-on (expected non-issue).

## 3. USB sheet (`Usb Connector.kicad_sch`) — FULLY REVIEWED, PASS after fixes

- **USB-C (J1, MC-711-H72)**: CC1/CC2 with individual 5.1k pull-downs (correct
  UFP), A/B pairs tied, VBUS caps 10µ+1µ+100n, shield to GND. PASS.
- **USBLC6 (D1)**: in-line on D+/D−, pass-through orientation correct (the
  historic D+/D− swap was fixed in an earlier session; verified again), VBUS
  pin on USB_VBUS. PASS.
- **FT2232H (U8)**: all power pins verified against DS pin table —
  **VPHY/VPLL are +3.3 V pins** (fed 3V3 via FB1/FB2 + 100 nF — CORRECT; an
  earlier review note claiming they should be 1.8 V was wrong; do not "fix").
  VREGIN=3V3, VREGOUT→VCORE (1.8 V) with 4.7 µF + 3×100 nF on pins 12/37/64;
  4×VCCIO decoupled; REF = 12k 1 % to GND (DS requirement); RESET RC
  (10k/100 nF); 12 MHz crystal Y1 (CL=12 pF part vs 18 pF caps — verified
  consistent); TEST→GND, AGND→GND.
- **EEPROM 93LC46B (U7)**: interface **was wrong** (DO+DI both direct to
  EEDATA) → fixed per DS Table 3.4: EE_DO net, R30 2.2k (C25879) to EE_DATA,
  R31 10k (C25744) pull-up to 3V3, DI direct. 93LC46B = fixed 16-bit org =
  correct for FT2232H. Verified in netlist.
- **FTDI↔flash/FPGA config pins**: **rewired 2026-07-18** to stock iceprog
  convention: SCK=ADBUS0, MOSI=ADBUS1, MISO=ADBUS2, FLASH_CS=ADBUS4,
  CDONE=ADBUS6, CRESET=ADBUS7 (verified against iceprog.c; old ADBUS3/ACBUS0/
  ACBUS1 now NC). R11/R12 10k pull-ups on CRESET/CDONE intact.
- **EEPROM contents decision**: ship blank (default 0403:6010 = what iceprog
  opens). Documented in TODO.

## 4. FPGA sheet (`Fpga.kicad_sch`) — FULLY REVIEWED, PASS

- **iCE40UP5K (U9, 4 units)**: VCC=1V2 (pins 5/30); VCCIO_0/2 + SPI_VCCIO1 =
  3V3, each decoupled; VPP_2V5 on 3V3 (standard practice, iCEbreaker does the
  same); VCCPLL via 100 Ω + 100 nF + 10 nF (Lattice filter); CDONE/CRESET 10k
  pull-ups; EP→GND.
- **SPI flash (U10 W25Q32JVSS)**: on the hard-SPI pins (14–17), WP/HOLD 10k
  pull-ups, shared correctly with FT2232 ADBUS0-2/4 (FTDI Hi-Z at reset; FPGA
  held in CRESET during FTDI flashing — iCEbreaker-equivalent arrangement).
- **Clocks**: X1 12 MHz oscillator → CLK12 on pin 20 (**G3 global**); EXI_CLK
  on pin 44 (**G6 global**). Both verified good pin choices.
- **Pin map** (authoritative, incl. 2026-07-18 debug additions): EXI_MOSI=4
  (in), EXI_MISO=3 (out), EXI_CLK=44, EXI_CS=45, EXI_INT=46, ETH bus=23–43,
  CLK12=20, GC_ON=21, ETH_RST=2, UART FPGA-RX=18/TX=19 (net names are
  FTDI-perspective!), LED_G=47, LED_R=48, DBG0–4=9/10/11/12/6.
- **Debug provisions added 2026-07-18**: D6/D7 LEDs + R37/R38, J4 header,
  TP1/2/4/5 (TP3 on ethernet sheet). Netlist-verified (LED polarity, TPs on
  global rails, not sheet-local orphans).

## 5. Ethernet sheet (`ethernet.kicad_sch`) — FULLY REVIEWED, PASS after fixes

- **W5100S straps/pins, all verified against DS pin table**: MOD[3:0]=0100 =
  "010X" parallel bus ✓; SCLK→GND = documented requirement for bus mode ✓;
  pin 32=MOSI/**A0**, pin 33=MISO/**A1** (matches WIZnet ref) ✓; CSn/RDn/WRn
  internal pull-ups (IU), DAT0-7 IOU ✓; **INTn is push-pull (type OP)** — no
  pull-up needed, do not add one ✓; RSTn is plain input (type IP) → R36 10k
  to ETH_3V3 added 2026-07-18.
- **1V2 loop**: 1V2O → C61 4.7 µF → FB3 100 Ω ferrite → 1V2A+1V2D with 5×100 nF
  — matches ref topology. 3V3A/3V3D common (ref's inter-rail ferrites are
  marked optional; single-net accepted).
- **RSET_BG**: 12.4k 1 % — DS says 12.3k; ACCEPTED (E192 value, WIZnet ref
  itself uses 12k+300R; 0.8 % immaterial). Closed.
- **Crystal Y2**: 25 MHz, CL=12 pF part (C9006) vs 18 pF caps → CL≈12 pF ✓
  (DS Table 9 wants 12 pF); mandatory external 1 MΩ feedback (R17) present ✓
  (DS: "W5100S has no feedback resistor"). FTDI ref-note: no series RExt
  (ref uses 0 Ω) — accepted.
- **MDI section — now implements the WIZnet ref schematic item-for-item**:
  49.9 Ω×4 (R26–R29, C25120) + 100 nF×2 (C18/C19) termination on the PHY-side
  nets; 3.3 Ω×4 series dampers (R32–R35, C137986) — chain per line:
  U11 pin → termination tap → 3.3 Ω → ESD → transformer; C20 100 nF + C21 1 µF
  center-tap bypass at J2 pins 4/5. Net naming: PHY_* (chip side) / MDI_*
  (damper→ESD) / ETH_* (ESD→jack); **all three groups are in the ETH_DP
  netclass** (patterns in `re-bba-rb.kicad_pro`).
- **D4/D5 (USBLC6 on the pairs) — SETTLED, do not re-litigate**: keep. ST
  rates USBLC6 for Ethernet; 2.5–3.5 pF OK at 100BASE-TX. Two deliberate
  details: (1) **pin 5 floats on purpose** (lines are 3.3 V-biased and swing
  above it; a tied rail would clip peaks; floating rail self-biases and the
  6 V zener still clamps); (2) **split nets force flow-through routing**
  (pins 1↔6/3↔4 are one internal node) — never merge the nets or stub the
  diode. Full reasoning in TODO.md.
- **Magjack J2 (HR911105A)**: transformer spec verified vs DS Table 11
  (1:1, 350 µH) ✓; LED wiring (R14/R15 330 Ω anodes to ETH_3V3, cathodes to
  LNKn/ACTn pins 17/20) — *assumed* internal LED pinout 9/12=anodes,
  10/11=cathodes: **confirm at bring-up** (no HR911105A datasheet in repo).
  Pin 8 (Bob-Smith common) + shield tied directly to GND — deviation from
  ref's 1 nF/2 kV chassis split, accepted deliberately (GC floats, no earth).
- **Ethernet layout (PCB) — reviewed twice (after rework + after insertion)**:
  termination 1–3 mm from U11 MDI pins; dampers in-line, MDI stubs
  1.45–1.48 mm; D4/D5 flow-through confirmed pad-by-pad; pair skew TX
  0.66 mm / RX 1.81 mm (fine at 100M — do not "improve"); pairs on F.Cu over
  solid In1 GND, one B.Cu crossover via per N line at the jack; **In1 plane
  correctly voided under the magjack cable/isolation side** (deliberate, keep);
  C20/C21 against the jack pin column (as close as the plane void allows);
  30 GND stitch vias in the corner; RX pair passes ~3–4 mm from Y2 (accepted,
  don't move closer); RSET_BG 2.8 mm with one via to B.Cu (plane-shielded, OK).

## 6. EXI sheet (`exi.kicad_sch`) — FULLY REVIEWED, PASS after DO/DI fix

- **DO/DI direction — SETTLED with hardware evidence, do not re-litigate**:
  YAGCD SP1 naming is **console-perspective**: pin 6 DO = GC data out =
  adapter MOSI *input*; pin 9 DI = GC data in = adapter MISO *output*.
  Evidence: SD Gecko straight-through table (MC pin 5 "DO" → SD CMD input,
  pin 7 "DI" → SD DAT0 output) + SD2SP2 (DO → OR gate → CMD). The board was
  wired backwards (following a wrong table in `docs/gc_bba_fpga_design.md`,
  since corrected); fixed as a pure rename + R21/R25 identity swap, zero
  copper changes. Final: J3.6(DO)→R21 22 Ω→FPGA pin 4 = EXI_MOSI;
  J3.9(DI)→R25 33 Ω→FPGA pin 3 = EXI_MISO.
- **PUSB3AB6 (D2)**: pinout verified vs Nexperia DS (1=CH1, 2=GND any-pin,
  3–7=CH2–6); DFN2111-7 matches the SON50P110X213X50-7 footprint; 0.15 pF/ch;
  rated for 3.3 V lines. Note: BOM part C49383400 is the **ElecSuper clone**
  ("(ES)"), pin-compatible — bring-up suspect only if ESD behaviour odd.
- **EXTIN**: 10k (R18) to **SP1_3V3 (the GC's own rail)** — correct, doesn't
  back-power. **12 V**: J3.5 → 12V_EXI (power tree). J3.8 (second 3.3 V pin)
  deliberately NC. Series elements: R24 100 Ω on EXI_CLK (input damping),
  R21/R25 as above. INT (J3.3) driven by FPGA pin 46 — gateware should use
  open-drain emulation (TODO).
- **J3 footprint provenance**: 12 contacts, 1 mm effective pitch, two
  staggered depth rows, **front side only**, fingers to the board edge (the
  `.kicad_dru` has a J3 edge-clearance exception for this). Geometry comes
  from the physical sp1_test_plug iterations — the test-plug project has no
  reusable footprint to diff (it only carries FFC breakouts). Outline/
  protrusion fit remain bench checks.

## 7. PCB global / JLCPCB — REVIEWED, PASS

- **DRC**: 0 errors / 0 unconnected / 0 parity as of each review point
  (remaining parity items = the 11 debug/fix footprints awaiting placement +
  3 FTDI reroutes + R3 value sync — all listed by F8). Warnings are
  silkscreen cosmetics only (~150; JLC auto-clips).
- **JLC capability floor**: encoded as error-severity rules in
  `re-bba-rb.kicad_dru` (0.09 mm trace/space, 0.15 mm drill, 0.2 mm
  hole-to-copper etc.) — passing. Diff-pair impedance rules (USB 90 Ω,
  ETH 100 Ω) are error-severity and passing; they police PHY_*/MDI_*/ETH_*
  and FT_D*/USB_D* via netclass patterns.
- **Stackup**: 7628 prepreg 0.2104 mm / 0.6 mm core ≈ 1.14 mm total =
  **JLC04121H-7628** (JLC nominal 1.2 mm, satisfies SP1 slot). Order with
  ENIG + gold fingers + 45° bevel (copper_finish field says "None" —
  cosmetic only). Board 102×33.4 mm.
- **Fiducials**: FID1–3 placed 2026-07-18 (board-only footprints) at
  (195, 68.5)/(131, 48)/(163, 44.5) — track-clearance verified after a first
  placement attempt collided with tracks (caught by DRC).
- **Zones**: In1.Cu = single solid GND plane; In2.Cu = 3V3 + ETH_3V3
  (priority 1) islands. No other zones.

## 8. BOM — FULLY AUDITED (netlist-vs-BOM count check passes)

All orderable components carry Footprint+Value+MPN+LCSC+Manufacturer.
Deliberate `in_bom no`: J3 (gold fingers), J4, TP1–5 — the **only** allowed
netlist/BOM delta. Spot-verified on JLC/LCSC: crystals CL=12 pF (C70565/
C9006, Basic), 49.9 Ω C25120, 3.3 Ω C137986 (YAGEO, Extended), 2.2k C25879,
150k C25755, LEDs C72043/C2286 (Basic), 12 V-rail ratings, 1 % tolerances on
R1–R4/R10/R16/R26–R38. D2 = ElecSuper clone (see §6).

## 9. Explicitly NOT reviewed / remaining risk (don't claim coverage)

- **Mechanical fit** (outline vs slot, RJ45/USB-C protrusion) — bench only.
- **HR911105A internal LED pinout** — assumed, confirm at bring-up.
- **W5100S register map in the gateware** — written from memory per
  CLAUDE.md; confirm at bring-up.
- **Actual power-on behaviour** (12 V inrush, mux transitions under load,
  FT2232+iCE40 enumeration) — bench only.
- **Gateware** (board PCF, GC_ON gating, UART crossover, INT drive style,
  LED/DBG driving) — tracked in TODO, not part of the hardware review.
- **`re-bba-rb.kicad_pcb.old.*` / `.history/`** — deleted/ignored, never
  reviewed for content.

## 10. Session/history notes an agent may need

- `datasheets/` was once deleted by an errant commit and restored from the
  local LFS object store; recovery recipe is in the git log of `4704dfb`.
- A stale case-colliding `power.kicad_sch` was removed (Windows checkout
  hazard — never add files differing only in case).
- The SP1 pin table in `docs/gc_bba_fpga_design.md` was the root cause of the
  DO/DI swap and has been corrected — trust it now; it carries a "do not
  swap" note with the evidence.