843 JA Achtung Full
843 : JA Achtung Full
- Author: Joel Kaplan and Amit Elmaliach
- Description: Two-player Achtung die Kurve: VGA output, QSPI PSRAM framebuffer, gamepad input
- GitHub repository
- Open in 3D viewer
- Open in Tiny Tapeout Explorer
- Open in VGA Playground
- Clock: 50000000 Hz
How it works
JA Achtung Full is the full two-player Achtung, die Kurve! engine for a Tiny Tapeout
1x2 footprint. Each player steers a continuously rotating head, leaves a
trail with periodic passable gaps, and loses on contact with a wall, either
trail, or the other head.
The chip stores its 640×480 framebuffer in an external QSPI PSRAM. Four 2-bit pixels are packed into each byte and the display streamer fetches 8-byte bursts (32 pixels) for VGA. During vertical blanking, the game engine uses the same PSRAM port for collision reads and read-modify-write trail updates.
Player positions use Q10.6 fixed-point coordinates and a compact quarter-wave lookup implements 64 movement directions. The angle phase registers each move's vector before address and collision calculation. A held boost button can add one extra move in a frame. Diagonal moves fill an adjacent side pixel so the trail remains continuous.
Both SNES-style controllers share the Gamepad PMOD serial interface. The lobby lets each player choose a distinct color before Start begins the round; disconnected all-ones controller data is ignored.
How to test
- Connect the VGA PMOD, QSPI PSRAM PMOD, and Gamepad PMOD.
- Assert
rst_nlow before powering the PSRAM. After PSRAM VDD is stable, keeprst_nlow for at least 150 us. During this hold the chip keeps the external PSRAM clock low, all chip-select outputs high, and all four SIO lines actively low, as required by the APS6404L power-up specification. The 50 MHz system clock may already be running. - Release reset. The chip issues the PSRAM reset and quad-enable sequence, waits the required reset recovery time, and displays the color-selection lobby.
- Use the D-pad to choose colors and A to confirm; Select unlocks a confirmed color. Press Start when both players are ready. The chip then clears the framebuffer while retaining the lobby overlay and starts the round. If both players confirm the same free color on the same report, player 1 reserves it and player 2 remains unconfirmed until choosing another color.
- Steer with Left/Right or L/R and use A for boost. After game over, Start rematches with the retained colors, or Select returns that player to the lobby and unlocks their color.
The automated suite in Game Simulation/tests/game_2x1/ compares 23
full-resolution and 24 coarse-resolution game traces with an independent
Python framebuffer model, captures a true 640×480 VGA frame through QSPI, and
drives the complete gamepad/QSPI/arbitration path.
External hardware
- Tiny Tapeout VGA PMOD
- APS6404L-compatible QSPI PSRAM PMOD
- Tiny Tapeout Gamepad PMOD with two SNES-compatible controllers
- VGA monitor
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | VGA R1 | Flash CS# (unused, high) | |
| 1 | VGA G1 | QSPI PSRAM IO0 | |
| 2 | VGA B1 | QSPI PSRAM IO1 | |
| 3 | VGA VSync | QSPI PSRAM SCK | |
| 4 | Gamepad PMOD latch | VGA R0 | QSPI PSRAM IO2 |
| 5 | Gamepad PMOD clock | VGA G0 | QSPI PSRAM IO3 |
| 6 | Gamepad PMOD data | VGA B0 | QSPI PSRAM CS# |
| 7 | VGA HSync | PSRAM B CS# (unused, high) |