Closes the remaining gaps in cross-board I2C so any topology of
supported boards (Uno↔ESP32, two ESP32s, Uno↔Uno↔Uno, ESP32-C3
connected to anything, etc.) works end-to-end with all I2C
components including write-only sinks (SSD1306, PCF8574, LCD-I2C).
Implementation (6 phases):
1. **BFS routing in I2CBusManager**: connectToSlave + handleExternalConnect
walk the bridge graph with a visited Set so multi-hop chains
(A↔B↔C with the device on C) resolve transparently. A new
forwarder-device shim is installed at intermediate hops so the
existing handleExternalWrite/Read/Stop machinery routes
through without per-method visited tracking.
2. **Per-peer proxy ownership in Esp32BridgeShim**: replaces the
global _proxiedAddrs Set with _proxiedByPeer Map so concurrent
bridges to the same ESP32 (e.g. wired to both Uno and Pico)
don't wipe each other's proxies on teardown. Interconnect's
per-wire teardown calls clearProxiesForPeer(peerBus) instead of
clearAllProxies.
3. **BFS-aware proxy sync**: syncProxyFromPeer now walks the peer
bus + its transitive bridges, so an ESP32 sees devices on
boards two or more hops away. _peerDeviceLookup keeps a flat
addr → device map for write-forwarding and resync.
4. **Periodic resync (250 ms)**: Esp32BridgeShim runs a setInterval
while any proxy is live, re-dumping each device with
dumpRegisters() and pushing updateProxyI2c only when an XOR-
stride hash changes. This keeps RTC time advancing visible to
ESP32 firmware without flooding the WS pipe with static
calibration dumps. Hash is primed during initial sync so the
first tick doesn't push a redundant identical buffer.
5. **Write-forwarding ProxySlave → peer**: backend ProxySlave
buffers write bytes during the transaction and emits a
`proxy_i2c_complete` event on STOP / repeated-START. Frontend
Esp32Bridge dispatches the event to a new onProxyI2cComplete
callback; the shim replays the byte sequence on the actual
peer I2CDevice via writeByte() + stop(). Makes ESP32 firmware
writes to peer SSD1306 actually repaint the OLED, peer PCF8574
latch updates, peer I2CMemoryDevice register mutations propagate.
6. **ESP32-C3 routed as bridge**: Interconnect.isBrowserSim no
longer claims c3/xiao-c3/c3-supermini — they were already
going through Esp32Bridge per the store's ESP32_RISCV_KINDS
routing, but Interconnect was treating them as browser sims
which broke proxy install. isEsp32Bridge now correctly
includes c3 family + ESP32-S3 + Arduino Nano ESP32.
Defensive: addBoard now disposes any existing shim's proxies
before overwriting simulatorMap entry so test reruns don't leak
timers.
Tests:
- 4 BFS multi-hop tests (i2c-multi-board-slave-gap.test.ts)
- 11 cross-board scenarios + per-peer + write-forward + resync
(i2c-esp32-multiboard-bridge.test.ts)
- 1 real-firmware E2E for write-forward via QEMU (compile +
load + observe proxy_i2c_complete arriving with the byte)
- New sketch fixture: esp32_i2c_write_to_peer.ino
Result: 90 test files / 1295 tests pass / 0 fail.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
- Implemented `i2c-esp32-real-firmware.test.ts` to test ESP32 I2C communication via backend and WebSocket.
- Created `load-example-transitions.test.ts` to ensure proper loading of examples between board-less and board-based contexts.
- Added `CircuitVerificationModal.tsx` to display circuit verification results before running simulations.
- Developed `circuitVerifier.ts` to perform pre-flight checks for circuit safety, identifying potential issues like short circuits and component overloads.
- Introduced minimal ESP32 I2C master sketch `esp32_i2c_writer.ino` for testing I2C transactions.
- Implement HD44780Decoder for decoding I2C commands to HD44780-compatible LCDs.
- Add bmp280_bridge_reader.ino to read BMP280 chip_id and status registers via I2C.
- Create i2c_scanner_multi.ino to scan I2C addresses and report responding devices.
- Introduce lcd_i2c_hello.ino to demonstrate basic LCD functionality with I2C.
- Implement pcf8574_bidirectional.ino to test bidirectional communication with PCF8574.
- Add pico_i2c_master_reader.ino for reading BMP280 from a Raspberry Pi Pico.
- Create rtc_lcd_clock.ino to display time from a DS1307 RTC on an I2C LCD.
- Implemented `esp32_spi_chip_demo.ino` to demonstrate SPI communication with a 74HC595 shift register.
- Created `esp32_uart_chip_demo.ino` for UART loopback testing with ROT13 transformation.
- Added Python tests for compiling chips and sketches, ensuring valid WASM output and successful compilation for various board families.
- Developed end-to-end tests for ESP32 with custom chips using I2C and SPI, validating synchronous communication through the backend.
- Introduced GPIO bridge tests to verify serial communication and GPIO state changes.
- Ensured all tests validate the expected behavior of the custom chips and their interaction with the ESP32 firmware.
David Montero Crespo