Skip to content

Sniffer PCB (designed, not used here)

A passive edge-connector interposer that plugs into both consoles' EXT ports, reproduces the null-modem crossover, and taps every signal for a logic analyzer.

Not used for this capture

This board was designed and is fab-ready, but the RE here used grabbers directly on the mainboard — Brazilian fab + shipping cost more than it was worth for a one-off. The design stays for anyone who wants non-invasive, repeatable captures.

Files: ngpc_link_sniffer/hardware/ (KiCad 10, gerbers included).

[NGP #1] ⇥ [SIDE A]══ sniffer ══[SIDE B] ⇤ [NGP #2]
                       │      │
                    [TAP A] [TAP B]  → logic analyzer

Design
Board 60 × 24 mm, 2-layer, tongues 11.5 mm wide (for a 12 mm slot)
Connector the board's gold edge is the plug — no original cable needed
Crossover TXD↔RXD, /CTS↔/RTS on opposite copper layers (cross without shorting); GND straight
Contacts 5 pads at 1.5 mm pitch, duplicated top+bottom (via-tied) so it mates either face up
Taps two 1×5 headers = each side's GND/TX/RX/CTS/RTS before the crossover

If you fab it

  • Thickness is the fit (the tongue is the blade): order 0.8 mm and 1.0 mm, test-fit.
  • Finish: ENIG for a proto; enable gold-fingers only on the final rev (it multiplies price).
  • Pad size/pitch and pin order are provisional — confirm with calipers + continuity to the SIO0 pins.
  • Single-console mode: wire a 3.3 V USB-UART to a tap (TX↔RX crossed) to play "fake console". Never 5 V.