hardbyte / hardbyte/python-can

no response from Kvaser after a long delay between messages

Offen
#2,017 0 Kommentare 0 Reaktionen 0 zugewiesene Personen Auf GitHub ansehen
bug
Vorherrschende Sprache
Python
Sterne
1.6k
Forks
697
PR-Merge-Kennzahlen
Keine gemergten PRs in 30 T.

Beschreibung

### Describe the error

When using the **Kvaser interface via python-can**, the CAN bus can automatically stop transmitting received frames (`bus.recv()` returns `None`) after a long period of downtime, even if:

* The CAN bus is still physically active,
* ECU responses are present on the wire (externally verified),
* "bus.send()" continues to run successfully without errors,
* Kvaser driver statistics report `status=ok` and no bus shutdown status.

As a result, python-can reports **false “no response” timeouts**, while valid responses exist on the CAN bus.

This happens without causing an exception and does not require a forced reinitialization of the bus to recover.

---

### For playback

1. Use python-can with **Kvaser leaf light v2** or **Kvaser U100**.
2. Open the CAN bus and connect to it in the normal mode (sending a request → receiving a response).
3. Leave the system in standby mode for a long time (about 1-5 minutes):

* The application is running,
* the tire is open,
* The Kvaser is connected,
* The control unit is connected and turned on.
4. After the waiting period has expired, send a new CAN request.

Observed behavior:

* `bus.send()` completed successfully.
* `bus.recv(timeout)` returns the value `None` until the timeout expires.
* Python exception is not generated.
* External monitoring confirms that ECU responses are present on the bus.

The problem occurs periodically, but can be fixed after sufficient downtime.

---

### Expected behavior

`bus.recv()` must continue to return incoming CAN frames after periods of downtime until:

* the tire is open,
* The hardware is connected,
* The driver does not report a bus shutdown or a passive status with an error.

At a minimum, python-can must either:

* automatic recovery or
* returns a clear error indicating that the reception descriptor has become invalid.

---

### Additional context

This is apparently due to ** inactivity of the Kvaser receive descriptor or internal buffering behavior** after a long downtime.

Observed characteristics:

* Kvaser Driver Statistics Report ('canGetBusStatistics', `canReadStatus'):

* `status=ok`
* "Bus load=0.0%"
* no overspending, no bus shutdown
* However, the function `bus.recv()` does not return any frames.
* Forced bus shutdown and reinitialization restore normal operation.

---

Operating system and version:
Windows 10 / Windows 11 (x64) (tested on both)

Python version:
Python 3.9

python-can version:
4.5.0/4.6.1 (tested on both)

python-can interface/s:
`kvaser`

---

Feedback and logs

*The Python feedback function does not start.*

Example of a diagnostic log collected after the timeout:

```
[KvaserSnap:frame_write]
statistics=std_data: 0, std_remote: 0, ext_data: 0, ext_remote: 0,
err_frame: 0, bus loading: 0.0%, overspending: 0 status=ok
```

Additional note:

* `bus.recv(timeout=0)` returns the value "None" again
* An external CAN analyzer confirms that the ECU responses are simultaneously present on the bus

Beitragsleitfaden

Beitragsleitfaden öffnen

Bewertung

Dieses Issue wurde noch nicht bewertet.

Neue Issues direkt in Ihr Postfach

Eine kurze Übersicht über anfängerfreundliche GitHub-Issues.