From 00082ac4910d526ea0ad85198d33bcade1d7412e Mon Sep 17 00:00:00 2001 From: Mikkeli Date: Tue, 13 Oct 2026 22:57:32 +0900 Subject: [PATCH] CAN docs: OBD-II is on the K-line via the ELM; nothing transmits on CAN Co-Authored-By: Claude Opus 5.5 Claude-Session: https://claude.ai/code/session_01DDwfd6Ki8UfG4hK6W5YpJz --- docs/BOM.md | 2 +- docs/impl/plans/CAN-BITRATE.md | 7 ++++--- 2 files changed, 5 insertions(+), 4 deletions(-) diff --git a/docs/BOM.md b/docs/BOM.md index e170d95..abc042e 100644 --- a/docs/BOM.md +++ b/docs/BOM.md @@ -31,7 +31,7 @@ All ports are taken. | **USB ID** | `0c72:000c` | | **Purpose** | USB-to-CAN adapter for reading car CAN bus traffic | | **Interface** | SocketCAN netdev | -| **Bitrate** | 500 kbps, measured on the Z27AG OBD port (not listen-only since 2026-10-12: obd-poller sends OBD-II requests; see [CAN bitrate plan](impl/plans/CAN-BITRATE.md)) | +| **Bitrate** | 500 kbps, measured on the Z27AG OBD port (not listen-only since 2026-10-12, though nothing transmits on CAN now: OBD-II goes over the K-line via the ELM327; see [CAN bitrate plan](impl/plans/CAN-BITRATE.md)) | | **Driver** | PEAK proprietary driver 9.2.0 (netdev build) — out-of-tree module, must be rebuilt after kernel updates | ### Notes diff --git a/docs/impl/plans/CAN-BITRATE.md b/docs/impl/plans/CAN-BITRATE.md index 2a21872..d480451 100644 --- a/docs/impl/plans/CAN-BITRATE.md +++ b/docs/impl/plans/CAN-BITRATE.md @@ -28,8 +28,9 @@ Persisted (boot and hot-plug): (svc-core), the single writer: the adapter now acknowledges frames like any scan tool. To go back, set `CAN_OPTS="listen-only on restart-ms 100"` there and replug the PEAK (or restart `can-up@can_pcan`). -obd-poller is **disabled since 2026-10-13**: the Z27AG's ECU never answered OBD-II on CAN (most likely K-line, pin 7, -not wired). The adapter was left acknowledging anyway, as harmless at the measured bitrate. +The Z27AG's ECU never answered OBD-II on CAN: it speaks ISO 9141-2 on the K-line (pin 7), confirmed through an ELM327 +on 2026-10-13. obd-poller now polls through that ELM over Bluetooth, so **nothing transmits on CAN**. The adapter was left +acknowledging anyway, as harmless at the measured bitrate. ## Goal @@ -57,7 +58,7 @@ Not set yet on purpose: no persistent bitrate until it's measured. **If every rate shows 0 frames:** the OBD port is probably behind a gateway that stays silent unless queried. Then the bitrate has to be found by sending one standard OBD-II request (ISO 15765-4: try 500k, then 250k), e.g. mode 01 PID 00 to `0x7DF`. That's transmitting, so it -belongs to the single CAN writer (`obd-poller`, project-yukart decision 3). Do it deliberately, not as part of a sniff. +belongs to the single writer (`obd-poller`, project-yukart decision 3). Do it deliberately, not as part of a sniff. ## After the rate is known