ESPCars

Monitor and modify your car with ESPHome — CAN and LIN, on cheap ESP32 hardware.

ESPCars is a collection of automotive ESPHome components. It turns an ESP32 into a vehicle bus node: observe traffic, decode signals into Home Assistant entities, bridge/filter/rewrite frames between buses, and talk to LIN devices — all configured in plain ESPHome YAML.

Components

Component	What it does	Targets
can_gateway	ISR-level CAN⇄CAN gateway: bridge, filter, ID-translate and patch frames between two buses; single-bus observe mode with signal decode into sensors; can_gateway.send, cyclic sends, per-ID statistics, bus-off recovery automations. See docs/can_gateway-user-guide.md	Any TWAI-capable ESP32 — observe/decode on one bus needs one controller (ESP32, S2, S3, C3, H2), forwarding needs two (C6, P4). Not the C5, see below
linbus	LIN bus master/slave: frame schedule, slave responses, sniffing (rx_ids / on_frame), checksum handling (classic/enhanced), self-test, detailed bus statistics. See docs/linbus-user-guide.md	ESP32, ESP32-C3, ESP32-C6
isotp	ISO-TP (ISO 15765-2) transport for diagnostics: segments requests and reassembles responses on top of a can_gateway port; normal / normal-fixed / extended addressing, flow control, isotp.send, on_message / on_error, per-instance diagnostic counters	ESP32-C6 (on can_gateway)
uds	UDS (ISO 14229) diagnostic client on top of isotp: requests, decodes and schedules polling for fields defined in a flashed .dcat catalog — no decode rules in firmware or YAML — and publishes them as sensors/text sensors; uds.read / uds.execute / uds.raw / uds.set_enabled. See docs/uds-user-guide.md	ESP32-C6 (on isotp)
sd_logger	SD-card bus datalogger: buffers CAN/LIN frames (via the generic sd_logger.log action or a native can_gateway tap) and ESPHome's own log into a RAM ring, drained by a dedicated writer task so SD latency never touches bus timing; rotation, crash-safe writes, card-failure recovery, and optional chunk collection over WiFi. Pure sink — never transmits. See docs/sd_logger-user-guide.md	ESP32-C6

Quick start

external_components:
  - source: github://kipp-ing/ESPCars
    components: [can_gateway, linbus]

can_gateway:
  ports:
    - id: car
      rx_pin: GPIO3
      tx_pin: GPIO2
      bit_rate: 500kbps

sensor:
  - platform: can_gateway
    port_id: car
    can_id: 0x2A0
    offset: 2
    length: 2
    name: "Battery Voltage"
    filters:
      - multiply: 0.01

See tests/build/ for complete, compiling example configurations of every feature.

Hardware

Developed against the ESP32-C6 reference adapter board (CAN + Modbus + LIN transceivers). Any ESP32 with the right transceiver works: a CAN transceiver (e.g. TJA1051, SN65HVD230) for can_gateway, a LIN transceiver (e.g. TJA1021) for linbus.

Warning: These components can transmit on vehicle buses. Writing to a car's CAN or LIN bus can trigger real actuators. Start in observe/listen-only configurations and only send frames you understand, on buses you own.

Development & testing

python3 -m venv .venv && .venv/bin/pip install -r requirements_test.txt
script/check.sh                              # pytest + clang-format + every config
.venv/bin/python -m pytest tests/ -q         # component schema/codegen tests
make -C tests/host                           # C++ unit tests for the ISR-side core
.venv/bin/esphome config tests/build/can_gateway/test.esp32-c6-idf.yaml   # validate
.venv/bin/esphome compile tests/build/can_gateway/test.esp32-c6-idf.yaml  # full build

tests/host/ compiles can_gateway/gateway_core.h — the rule engine, slot pool, frame rings and recovery backoff that run inside the RX interrupt — with a plain host compiler under ASan/UBSan, because that header is deliberately free of ESPHome and ESP-IDF dependencies.

CI runs the schema tests and the host tests, validates every build config, and compiles the full target matrix on every PR.

Beyond CI there is a permanent hardware-in-the-loop bench — three reference boards (Mr. Green, Mr. Blue, Mr. Orange) running a token ring across LIN and two gateway-bridged CAN segments under load. See tests/hil/HIL.md; script/hil/verify.py must exit green before a release.

License

Same dual-license scheme as ESPHome: C++ under GPLv3, Python and everything else under MIT. See LICENSE.