Files
evan b22934fe0d Replace vvfat SD with browser-built raw FAT32 from OPFS
Browser SD files are persisted in OPFS (web/sdstore.js) and edited in the
Files tab. At boot the browser builds a deterministic 64 MiB FAT32 image
(web/fat32.js) with nested directories and VFAT long names, then mounts
it as a raw block device, bypassing QEMU's broken populated-vvfat WASM
coroutine path. Guest writes mutate only the ephemeral image.

Exposes a hidden #frame-generation indicator that increments on every
e-ink flush, so automation can wait on real display updates instead of
fixed sleeps. Adds tests/ with a Makefile runner: 'make test' for JS +
FAT32/mtools checks, 'make browser-test' for a headless-Firefox boot of
the official CrossPoint 1.4.1 firmware that navigates to
Test/example.txt. Bumps third_party/qemu to the SPI-SD/CMD13 fixes and
updates README/ROADMAP/ISSUES for the new architecture.
2026-07-21 07:43:07 -04:00

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# xteink-web-emulator
An offline, in-browser emulator for the xteink **X3/X4** (ESP32-C3 + e-ink):
upload a firmware `.bin`, run the real machine code client-side, see the screen,
press buttons, mount a virtual SD — no server, no proprietary engine.
**Status:** native and WebAssembly builds provide one `xteink` machine that
selects X3 or X4 at launch. Unmodified
[canonical firmware](https://github.com/crosspoint-reader/crosspoint-reader)
auto-detects the selected variant: X3 boots with its UC8253 display and SD card;
X4 reaches its SSD1677 driver through a blank protocol stub. A basic static
browser UI now loads local firmware, renders the panel, and drives the physical
buttons. See [ROADMAP.md](./ROADMAP.md) for architecture and plan.
## Quick start (native QEMU)
```sh
git clone --recursive https://github.com/crosspoint-reader/crosspoint-reader ../crosspoint-reader
# Build ../crosspoint-reader's PlatformIO `default` environment first.
nix develop
make qemu # clone espressif/qemu @ pinned commit, apply patch, build
make firmware sdimage # 16 MB flash.bin + FAT32 sd.img from the PlatformIO build
make run # X3 (default)
make run VARIANT=x4 # X4 detection + blank SSD1677 stub
```
Point at a firmware build with `make firmware FIRMWARE_DIR=/path/to/.pio/build/gh_release`.
`make qemu` is a long compile on modest hardware — set `JOBS` to taste.
## WebAssembly build
Podman or Docker is required. The QEMU source is the `third_party/qemu`
submodule, so initialize it first:
```sh
git submodule update --init third_party/qemu
```
The build is limited to `riscv32-softmmu` and the X3/X4 device graph;
networking, audio, virtfs, tools, docs, and unrelated boards are disabled.
```sh
make qemu-wasm
# dist/wasm/qemu-system-riscv32.{js,wasm,worker.js} + esp32c3-rom.bin
```
The build runs Node smoke checks when Node is available.
## Browser interface
```sh
make web
# Open http://127.0.0.1:8000/web/
```
Choose a CrossPoint firmware `.bin` — either the ~5 MB release app image (it is
merged in-browser with the bundled bootloader and partition table into a 16 MB
flash) or a full 16 MB image — select X3 or X4, and boot. The controls
map to the device's ADC button ladders and active-low Power GPIO. `make web`
serves the required COOP/COEP headers for Emscripten pthreads; a generic static
server without those headers will not work.
Real firmware boots in WASM and drives the X3 panel (528×792). Browser SD files
are persisted in OPFS and edited in the Files tab. At boot, the browser builds a
64 MiB raw FAT32 image with nested-directory and VFAT long-name support; QEMU
mounts that image directly, avoiding `vvfat`. Choose **Apply & reboot** to expose
edits to the guest. Guest writes modify only the ephemeral image. The Debug tab
reports committed WASM heap, visible MEMFS data, and browser JS heap where
supported. X4 remains a white display stub.
## Contents
- `qemu/patches/0001-xteink-machine.patch` — the `xteink,variant=x3|x4` machine
and its device models (I²C fingerprints, ADC, GPIO, SPI2, X3 UC8253, X4 panel
stub, SD-over-SPI fix), applied onto the pinned espressif/qemu commit by
`scripts/build-qemu.sh`.
- `third_party/qemu` — submodule of the [xteink QEMU fork](git@ssh.gitea.va.reichard.io:evan/qemu-xteink.git)
(espressif/qemu + the machine models + the wasm32 TCG backend), built for the
browser by `scripts/build-qemu-wasm.sh`. Edit it in place; `make web`
recompiles incrementally. `qemu/wasm/Dockerfile` is the pinned Emscripten
dependency environment.
- `flake.nix` — the espressif-qemu *release* binary as the fast generic baseline
(`nix run .#run-upstream -- flash.bin`), plus a devShell with QEMU's full build
environment. `Makefile``qemu`, `firmware`, `sdimage`, `run`, `chip`.
- `web/fat32.js` and `web/sdstore.js` — dependency-free FAT32 image generation
and persistent OPFS file storage.
- `scripts/mksd.sh` — build a FAT32 SD backing image for native QEMU.
- `tests/``make test` runs JS/FAT32 checks; `make browser-test` boots the
official CrossPoint 1.4.1 firmware and navigates to `Test/example.txt` in
headless Firefox.
- `chip/eink-x3.chip.c` — the reverse-engineered X3 e-ink protocol, first written
as a Wokwi chip and now the reference for the QEMU display device.
`make -C chip test` runs its host self-check.
## Why not Wokwi
Wokwi runs any bin in a browser and we had the e-ink chip working — but its
simulation engine is proprietary and gated behind a license/service, so it can't
be self-hosted or run airgapped. QEMU is the open path; the e-ink protocol work
carried straight over.