0xrsydn/gameboy-rust
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feat(cartridge): add explicit GPIO and RTC control support

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0xrsydn 2026-10-07 05:28:52 +07:00
commit 692be36349
18 changed files with 889 additions and 26 deletions
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docs/research/emerald-reset.md
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@ -25,8 +25,8 @@ Byte, halfword, word, block-store, and DMA validation retain explicit errors wit
Use a local ROM that you may lawfully use:
```sh
direnv exec . cargo run --locked --release -- --rom roms/pokemon-emerald.gba --steps 1000000
direnv exec . cargo run --locked --release -- --rom roms/pokemon-emerald.gba --window --frames 120
direnv exec . cargo run --locked --release -- --rom roms/pokemon-emerald.gba --rtc --steps 2000000
direnv exec . cargo run --locked --release -- --rom roms/pokemon-emerald.gba --rtc --window --frames 60
```
The earlier reset-only implementation stopped at master sound enable (`0x04000084`, PC `0x082e0518`).
@ -64,13 +64,18 @@ A child cannot start itself without a parent clock. No linked transfer, assigned
The send register supports 16-bit data; receive latches do not become invented peer data.
See [the register model and evidence limits](../hardware/serial.md#disconnected-multiplayer-configuration).
Both terminal and native runs now reach a Game Pak GPIO control write:
Multiplayer configuration then reached a Game Pak GPIO control write (`0x080000c8`, PC `0x082e29f8`).
The optional [cartridge GPIO/RTC interface](../hardware/cartridge-gpio.md) now supports read enable, directions, pin latches, and RTC control transactions.
Select it explicitly with `--rtc`; ordinary ROM bytes and other ROMs' default hardware remain unchanged.
No host date, RTC calendar, or successful calendar read is invented.
Both terminal and native runs with `--rtc` now reach a calendar-read command:
```text
Steps: 956055; instructions: 953375; IRQ entries: 80; DMA units: 2600; HALT idle: 0
Nominal cycles: 3514932
PC=0x082e29f8
read-only memory at 0x080000c8
Steps: 957729; instructions: 955049; IRQ entries: 80; DMA units: 2600; HALT idle: 0
Nominal cycles: 3520685
PC=0x082e28a6
unsupported RTC calendar access: write 0x07 at 0x080000c4
```
The native run captures twelve startup frames. These do not establish a working title screen or gameplay.
@ -85,10 +90,11 @@ Workspace debug/release tests, strict Clippy, public ARM/Thumb/memory/BIOS check
Native ROM-window tests and graphics smoke modes pass on Darwin arm64.
The pinned Pong debug/release reports match.
The next requirement is cartridge GPIO, starting with the control register at `0x080000c8`.
Research the Game Pak data/direction/control registers and real-time clock protocol before implementing them.
Keep ordinary ROM writes read-only. Do not hide the failure by ignoring every cartridge write.
This serial result does not establish linked gameplay or serial GPIO interrupt support.
The next requirement is RTC calendar transfers with an explicit clock-source model.
Implement validated date/time formats, read snapshots, writes/reset, and clock ownership without putting host time in the core.
Keep battery persistence and cartridge IRQ behavior explicit; do not equate GBA STOP with stopping a battery-powered RTC.
Ordinary ROM writes remain read-only. Without `--rtc`, the earlier GPIO diagnostic is still expected.
This result does not establish gameplay, linked transfers, or cartridge/serial GPIO interrupt support.
Noise now has deterministic counter clocks and shares tested length/envelope logic with the independent pulse channels.
Sweep applies only to channel 1. Direct Sound has FIFO clocks and nominal DMA requests.