A2ext dvi

a2ext-dvi

Revision 0.3 uses A4 landscape with enlarged text: 1.524 mm pin names, wire labels and values, 1.27 mm pin numbers, and 1.778 mm references/notes. The revised layout preserves all electrical connections.

Passive DVI video daughterboard using an HDMI Type A connector and the PRD's 270 ohm series resistor network. Open the KiCad 10 project; symbols are local. The SH pin represents all four plated shell contacts. The physical PCB selects Kycon KDMIX-SL1-NS-WS-B15 for PCB-P2-THT. All 19 signal contacts and four shell tabs are through-hole. This upright right-angle port exits the right board edge; its approximately 16.4 mm body height and panel opening require a new fit check. The PCB-P1 Molex connector cannot fit this revision.

The 45 x 45 mm two-layer board uses axial 1/4 W DIN0207 270 ohm resistors (7.62 mm formed pitch), a 5.0 mm pitch radial ceramic capacitor, and a bottom-mounted 2x10 female socket at J1. H1/H2 are 2.7 mm spacer holes aligned with the carrier. Resistor-to-HDMI pairs use a single layer per pair without vias: D0/D1 on F.Cu and D2/clock on B.Cu. Output tuning keeps intra-pair trace-length difference below 0.020 mm. Full routed lengths are in validation/summary.json; the carrier and IDC-to-resistor segments are not pair-length tuned. Controlled impedance and physical signal quality are unqualified. See fabrication notes, Gerbers and drills, top, bottom, and assembly plots. DRC, ERC, and schematic parity reports in validation/ have zero findings. No SMD assembly or solder stencil is required. All four shell tabs require plated slots; retain both drill files when ordering. tmds-routing.json preserves the reviewed pair tracks during regeneration; the placement generator locks them before routing the other nets.

Each conductor has a 270 ohm, 1% resistor. Shields, pin 17, shell, and both IDC ground contacts share GND. Pin 18 receives the carrier's fused +5V_DB supply; there is no additional series diode drop on this board. C1 decouples that rail. UART, RUN, 3.3 V power, GPIO35/44-47, DDC, HPD, CEC, and utility are unused.

The bundled libdvi program uses the lower GPIO for the positive conductor when invert_diffpairs=false. Use PIO1 base 16 and 64-bit mask helpers. Its clock generator uses the shared PWM slice for even/odd GPIO42/43. This is the reference's resistor-driven signaling approach, not a claim of HDMI compliance.

Initially use direct carrier mating. No ribbon cable length is qualified. Validate a fixed 640x480 timing mode, pair polarity, eye/edge quality, connector +5 V, and lock on multiple monitors with a real board. No EDID negotiation or hotplug handling is implemented by this schematic. Carrier power comes from the slot input (or an off-host fixture at that input); USB is data only.

Validation so far: ERC and named-net export checks. Firmware and physical TMDS tests are pending. From the repository root:

python3 tools/schematics.py dvi
python3 tools/check_schematics.py a2ext-dvi

References: ref/A2DVI v5.x hardware and ref/A2DVI-Firmware/libraries/libdvi/dvi_serialiser.{c,pio}.