td-io is a JVS I/O board designed to adapt older JAMMA-compatible cabinets to the newer JVS standard, used by modern arcade hardware such as the Naomi and exA. It features a number of independent systems to translate signals, drive cabinet hardware, and power JVS games.
The JVS I/O bus connects to the board via USB-style A and B connectors. Daisy chaining is supported. The I/O presents two players, each with a single joystick/lever and six buttons. Joystick and button 1-4 inputs are mapped to the JAMMA edge connector, and buttons 4-6 are mapped to a CPS2-style kick harness connector. Buttons are polled synchronously, ensuring microsecond-level latency.
The board also presents one or two coin slots, toggleable by a DIP switch. The board also features two coin meter drivers and two coin lockout drivers. Coins are locked out when the respective coin count is set to its max value (16383).
The board maps JVS-level video (0.7Vp-p, AC or DC coupled) to JAMMA levels (0-3V, DC coupled). This is achieved via a DC restore step using the sync signal, followed by a fixed amplification. The DC coupled output allows maximum compatibility with monitors such as the Nanao MS8 and capture devices such as the Splitfire which require it.
TD-IO provides a class-D audio amplifier, which can drive both mono and stereo speakers in JAMMA cabinets. For mono cabinets, audio is simply provided via the JAMMA edge. For stereo support, the cabinet's speakers should be connected to the JST NH header provided on the I/O. The pinout of this header is directly compatible with the Egret 2, and adapters can be easily made for other cabinets, such as the Aero.
The stereo/mono switch selects whether to mixdown the L/R channels to mono. It should be set to mono when using a mono cabinet via the JAMMA edge, and stereo when using a cabinet with the stereo header.
The stereo support is not directly compatible with nonstandard Neo Geo style stereo over JAMMA, with a common ground. For these cabinets, either use the TD-IO in mono mode, or rewire the cabinet to connect directly to the stereo header. The left/right negative speaker outputs should not be tied together.
An 8-pin JVS power connector forwards 12V and 5V from the cabinet to the JVS board. In addition, an on-board power supply generates 3.3V at up to 7A from the cabinet's 5V rail for systems that require it, such as Naomi.
The cabinet's 5V power supply must still be adequate to power the 3.3V converter.
To update the firmware, turn off power to the cabinet (if attached). Then, attach a USB cable to the micro USB connector. Hold down the white button on the RP2040 while plugging the USB connector into a PC. The TD-IO will then appear as a flash drive. Copy the firmware file (ending in .uf2) onto the drive. The TD-IO will then disconnect and be ready for use.
The board features an unpopulated expansion header exposing 3 3.3V level analog inputs, designed for potentiometers for analog joystick or racing games. This feature is experimental and not yet implemented in the firmware.
