svc-core/README.md

---
type: reference
---
# Core services

Part of **Project Yukart**, making an old 2008 Mitsubishi Z27AG a bit smarter with modern technologies.  
This file serves as the minimalist portal to other docs


## What this repo is about

The acquisition and processing cluster on the Orin, developed and deployed as one
unit: `recorder`, `decoder`, `gnss`, `imu`, `orin-status` and `obd-poller` now; `can-bridge` as it is
needed.

| Binary | Installed as | Does |
|---|---|---|
| `recorder` | `yukart-recorder.service` | Raw CAN + GNSS to disk, in sessions, under a storage bound; every `yukart/vehicle/*` value (decoded and OBD-II) beside them |
| `decoder` | `yukart-decoder.service` | The car's own broadcast frames to named signals (`yukart/vehicle/*`): every `z27ag` signal in contracts' `signals.json`, laid out by its `can` block. Booleans on change, numbers ≤ 20/s, each refreshed once a second; reads only |
| `bus-bench` | not installed: a test tool | Raw CAN and decoded-signal load over MQTT, measured: loss, latency, broker CPU ([report](docs/impl/reports/BUS-BENCH.md)) |
| `obd-poller` | `yukart-obd-poller.service` | OBD-II mode 01 on the K-line through the Bluetooth ELM327 (address in `/etc/default/yukart-elm`), the single writer to the car; never on CAN. The `obd_*` signals, calibration references (`yukart/vehicle/*`): rpm, speed, throttle, load, MAF, timing, O2 every round; temperatures and trims every 5 s. Lets go of the adapter after a minute of ECU silence |
| `gnss` | `yukart-gnss.service` | gpsd's fix as single values on `yukart/gnss/*`: fix, speed, heading, position, altitude, satellites |
| `imu` | `yukart-imu.service` | The WT61 (plus) on any USB-UART adapter, found by itself (adapter and speed), turned into the car's frame (`--forward`, `--right`): roll, pitch, gravity-free longitudinal and lateral g, yaw rate on `yukart/imu/*`, at most every 40 ms. Never writes to the module |
| `orin-status` | `yukart-orin-status.service` | The Orin's health on the bus, once a second: temperatures, CPU/GPU load, memory, power, fan, WiFi (with SSID)/LTE/tablet links, the CAN interface, the ELM's Bluetooth link, UPS battery (`yukart/host/*`). Powers the Orin off cleanly when the UPS pack stays below 11.0 V while discharging for 30 s |

```bash
scripts/deploy-recorder.sh                 # build, glibc check, install on the car Orin
scripts/deploy-native.sh BIN               # build BIN on the development Orin, glibc check, install;
                                           # deploy-{decoder,gnss,obd-poller,orin-status}.sh wrap it.
                                           # Redeploy after any contracts signals.json change
yukart-decoder --list                      # the signals it decodes, and where
zstdcat can-*.log.zst | yukart-decoder --replay   # what it would publish for a recording
scripts/replay-session.sh SESSION_DIR [SKIP_S]   # on the Orin: replay a session's frames through a
                                           # decoder on vcan_replay, live to displays; never recorded
yukart-obd-poller --elm ADDR --once        # on the Orin, service stopped: adapter, protocol,
                                           # supported PIDs and one value each
yukart-gnss --once                         # the next fix as JSON, no broker
yukart-imu --once                          # find the WT61, 3 s of readings as JSON, no broker
yukart-orin-status --once                  # on an Orin: one reading as JSON, no broker
yukart-recorder ctl status                 # on the Orin
yukart-recorder ctl start "cold start"     # manual session, ends only on stop
yukart-recorder ctl mark "indicator left on"
yukart-recorder ctl stop
```

Recordings live in `/var/lib/yukart/recordings/`, one directory per session —
layout in [the initial plan](docs/impl/plans/INITIAL.md#session-layout).

- For implementation practice guidelines, refer to the [guidelines](docs/GUIDELINES.md);  
- For implementation plans and history, refer to [them](docs/impl/);