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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 peripheral models done for the X3. Unmodified canonical
+firmware boots to the home screen, mounts a FAT32 SD image, lists its files, and
+responds to button presses under a patched espressif-qemu. The browser (WASM)
+port is next. See [ROADMAP.md](./ROADMAP.md) for architecture and plan.
+
+## Quick start (native QEMU)
+
+```sh
+nix develop
+make qemu             # clone espressif/qemu @ pinned tag, apply patch, build (JOBS=2)
+make firmware sdimage # 16 MB flash.bin + FAT32 sd.img from a PlatformIO build
+make run              # boot the xteink-x3 machine (add `-display none` for headless)
+```
+
+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.
+
+## Contents
+
+- `qemu/patches/0001-xteink-x3-machine.patch` — the `xteink-x3` machine and its
+  device models (ADC, GPIO, SPI2, UC8253 e-ink, SD-over-SPI fix), applied onto
+  the pinned espressif/qemu tag by `scripts/build-qemu.sh`.
+- `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`.
+- `scripts/mksd.sh` — build the FAT32 SD backing image (local-disk impl of the
+  SD block interface).
+- `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.