Software knows functions; hardware knows pins
A USB controller produces button and directional events. Our proposed one-player USB2JAMMA translates those into logical arcade actions and then assigns them to positions on a DB15 controller port. That last step matters because superguns that look alike can place their extra buttons or Coin signal on different pins.
For example, public manuals for HAS v4/v5 and SmallCab Deluxe v2.2 describe different arrangements around DB15 pins 2, 3, 9 and 10. A software mapping can model the difference. It does not certify the electronics that must safely drive the real contacts.
What our profile generator verifies
The private engineering repo records two source/manual-modeled families: HAS and SmallCab. A generated comparison matrix is derived from the firmware's profile definitions, and its static checks ensure that a programmable output is used no more than once and is confined to the intended button/switch pin set.
DB15 pin 1 is treated as ground and pin 8 is excluded from the programmable sink mask because it belongs to the power domain. A separate Service or Test action in a controller mapping does not create a physical Service or Test wire on superguns whose DB15 specification omits it.
Evidence labels should be public
| Status | What it means | What it does NOT mean |
|---|---|---|
| Manual-profiled | Software mapping matches a cited model/revision document | Electrical operation or reliability proven |
| Bench-tested prototype | A named board and configuration passed recorded checks | All revisions, power conditions and controllers supported |
| Qualified compatibility | Repeatable electrical, power-sequence and usage tests for specified hardware | Every connector with the same shape is compatible |
| Research concept | A possible circuit or feature is under discussion | Approved parts list or purchasable device |
Why the output should behave like a switch
Many supergun controller inputs expect a passive switch closure to ground. A robust adapter must emulate that behaviour, rather than assuming it can force a logic high into an unknown input circuit. Our design language therefore distinguishes RELEASED and SINK_LOW as requests to a properly engineered output stage.
An output device must stay released when the MCU is unpowered, reset, disconnected or recovering from a controller error. Backfeed, leakage, asserted-low voltage, signal timing and startup glitches are engineering measurements, not features to infer from a datasheet headline.
The measurement gates we wrote down
The research decision record defines prospective checks for 13 switch channels, default release, a suitably low asserted voltage, low leakage when released, a bounded stage delay, MCU-off release and no unintended activation during power transitions. Several low-side device families were compared on paper.
The important word is prospective: these are acceptance criteria for future measurements. We are not representing them as tests already passed or announcing a final output IC. Any chosen board revision needs its own documented evidence.
What this changes for customers
- A future product page should name exact supergun models and PCB revisions, not simply say 'Neo Geo DB15 compatible'.
- An installation guide should show connector orientation, known modes, power requirements and unsupported functions.
- Compatibility tables should say whether a row is based on a manual, a laboratory observation or repeated field use.
- A product should not be offered until a defined hardware revision completes the qualification checks.
Why this matters before the first sale
Publishing this research is useful because it explains how we intend to earn a supported-device list. The workshop can present a source-backed profile today and still clearly acknowledge the absence of electrical qualification.
USB2JAMMA remains a development candidate. The site does not sell the adapter, guarantee latency or claim tested compatibility with HAS, SmallCab or any other supergun.
Sources and further reading
Original documentation and specialist references consulted for this article. Always check your model and revision.
Information only: no product compatibility test is being claimed. These workshop accessories are not yet for sale.