--- type: plan status: ready updated: 2026-10-12 --- # Z27AG decoding captures: what to do in the car Recordings that let the broadcast frames be decoded: one thing changes at a time, each change is marked, and OBD-II mode 01 values are recorded alongside as the ground truth. Prior art and first candidates: [the prior-art report](../reports/Z27AG-CAN-PRIOR-ART.md). ## What records what | In the session directory | From | Use | |---|---|---| | `can-*.log(.zst)` | the PEAK, every frame, kernel timestamps | what gets decoded; also holds every OBD request (`7DF`) and reply (`7E8`) | | `vehicle.ndjson` | `obd-poller` via the bus | the same OBD replies as values (rpm, speed, throttle, load, MAP, MAF ~10 Hz; coolant, intake air, fuel 1 Hz); `env.timestamp` equals the reply frame's timestamp | | `events.ndjson` | marks from the app | when each step happened | | `gnss.ndjson` | gpsd (SIM7600) | speed and position for the drive | ## Operating the recorder from the app - **Sessions start by themselves** when the PEAK sees traffic (ignition on) and end 15 s after it stops. There is no start/stop button; nothing to do. - **Marks:** the **Mark** button → a quick chip, or type in *Other* and press enter. A mark is stamped when the recorder receives it, on the same clock as the frames. - **Check it landed:** the *Commands* list, at the top of the raw-messages pane (right side, or the lower half on a narrow screen), shows `✓ ok: mark 3 in 000042-…`. `✗ error: no session` means no traffic yet: ignition on, PEAK plugged. A mark sent with the link down waits (`unacked`) and goes when it is back, with its delay noted in the mark. - **OBD is working** when `engine_rpm`, `vehicle_speed_kph` and the rest appear in the signal list and move. If they never appear, see *If OBD stays silent*. ## Marks Type the step number first, then what is happening: `3 brake on`, `3 brake off`. One mark when an action starts and one when it ends is enough; a slow, steady action between them beats a quick one. Wait about 3 s between steps. ## Checklist **Before:** PEAK on the OBD port, Orin up, tablet connected. Engine off, doors shut. ### Parked, ignition on, engine off | # | Do | Mark | Finds | |---|---|---|---| | 1 | Nothing for 20 s | `1 baseline` | the resting values of every ID | | 2 | Accelerator: slowly to the floor over 5 s, hold 3 s, slowly back | `2 accel start` / `2 accel end` | pedal position (engine off: no rpm to confuse it) | | 3 | Brake: press, hold 3 s, release; three times | `3 brake on` / `3 brake off` each time | brake switch, maybe pressure | | 4 | Clutch: same, three times | `4 clutch on` / `4 clutch off` | clutch switch | | 5 | Steering: centre → full left → full right → centre, slowly | `5 steer start` / `5 steer end` | steering angle | | 6 | Gears: 1, 2, 3, 4, 5, R, neutral, 3 s each | `6 gear 1` … `6 gear R`, `6 neutral` | reverse switch (gear position if broadcast) | | 7 | Handbrake up, down, up | `7 handbrake on` / `off` | handbrake switch | | 8 | Indicator left 5 s, right 5 s, hazards 5 s | `8 left`, `8 right`, `8 hazard`, `8 off` | indicator states | | 9 | Side lights, dipped, main beam, flash, fogs, off | one mark each | light states | | 10 | Each door open/close, boot, bonnet | one mark each | door switches | | 11 | Wipers int / low / high / off, washer | one mark each | wiper states | | 12 | A/C on / off, blower up / down | one mark each | A/C request | | 13 | Seatbelt on / off | `13 belt on` / `off` | belt switch | ### Engine running, parked | # | Do | Mark | Finds | |---|---|---|---| | 14 | Cold start if possible; idle 60 s | `14 engine start` | coolant and oil warming; idle control | | 15 | Revs in steps: hold 1500, 2000, 3000 rpm 5 s each, back to idle | `15 rpm 1500` … `15 idle` | engine speed (OBD rpm is the reference), throttle against pedal | | 16 | Three sharp blips | `16 blips` | response timing of throttle, rpm, MAP | | 17 | A/C on 20 s, off | `17 ac on` / `off` | compressor clutch, idle-up | | 18 | Idle until the radiator fan cuts in, if it will | `18 fan` | fan state, coolant threshold | ### Driving (a passenger types the marks, or skip them) | # | Do | Mark | Finds | |---|---|---|---| | 19 | Pull away; steady 20, 40, 60 km/h for 10 s each where safe | `19 steady 20` … (optional) | road and wheel speeds against OBD and GNSS speed | | 20 | A gentle stop, a firmer stop | `20 stop` (optional) | brake pressure, deceleration | | 21 | A few corners each way | — | yaw / lateral g, wheel speed differences | | 22 | Each gear through the box | — | gear (from rpm ÷ speed if not broadcast) | Speed needs no marks: OBD speed and GNSS speed are recorded continuously. The drive is the important part; the parked steps can be split over several sessions. ## If OBD stays silent `yukart/system/obd-poller` says why (visible in `mosquitto_sub -v -t 'yukart/system/#'` on the Orin): - `bus idle: not polling`: no traffic: ignition off or PEAK unplugged. - `no ECU answers 01 00`: the engine ECU does not do standard mode 01 on this bus. Then OBDb's MUT-III (`21 xx`) requests are the next thing to try. - To see what answers, on the Orin: `sudo systemctl stop yukart-obd-poller`, `yukart-obd-poller --once` (supported PIDs and one value each, with reply times), `sudo systemctl start yukart-obd-poller`. Never two pollers at once: their replies would cross. ## Afterwards Sessions are in `/var/lib/yukart/recordings/` on the car Orin. Copy one off with `rsync -a mikkeli-orin-nano:/var/lib/yukart/recordings// …` into `yukart-data`, with a line in its README of what was done.