1. Overview
This article explains how Ruptela devices prioritise tachograph data sources for the TCO, TCO_CAN, and CAN parameter groups. Because there is no automatic fallback between sources, you must manually adjust the device configuration when a primary source is unavailable.
1.1 Parameter Groups and Sources
Tachograph data is organised into three parameter groups:
TCO – e.g. TCO first driver ID, TCO first driver state, TCO second driver ID
TCO_CAN – e.g. TCO_CAN total driving time, TCO_CAN current activity duration
CAN – e.g. CAN first driver ID, CAN tacho driver 1 card, CAN second driver ID
The table below shows which parameter groups each source can provide.
Parameter Group | K-Line | Tacho Read | FMS |
TCO | ✔ (Priority 1) | ✔ * | ✔ ** |
TCO_CAN | — | ✔ (Priority 1) | ✔ *** |
CAN | — | — | ✔ (Only source) |
* Tacho Read provides TCO only if K-Line TCO mode is disabled.
** FMS provides TCO only if K-Line TCO mode and Tacho Read are both disabled.
*** FMS provides TCO_CAN only if Tacho Read mode is disabled.
1.2 Source Priority Rules
Each source has a fixed priority. The device always uses the highest-priority active source and ignores the rest.
K-Line (tachograph K-Line interface) – Highest priority for TCO parameters. When K-Line TCO mode is enabled, TCO data is read exclusively from this source.
Tacho Read (tachograph CAN interface) – Primary source for TCO_CAN parameters. Also reads TCO parameters if K-Line TCO mode is disabled.
FMS (vehicle FMS connector) – Only source for CAN parameters. Also reads TCO_CAN and TCO parameters if both K-Line and Tacho Read are disabled.
⚠ Warning: Ruptela devices do not fall back to another source automatically. If the active source fails, you must disable it in the configuration so the next-priority source takes over.
📋 Recommendation: Before disabling a source as a workaround, always investigate and attempt to resolve the issue with the original source first. Switching sources should be a temporary measure, not a permanent fix. Re-enable the original source once the underlying problem is resolved.
1.3 Examples
⚠ Recommendation: Always investigate and attempt to resolve the issue with the primary source before disabling it. Switching to a fallback source is a workaround, not a fix — the root cause (e.g. a wiring fault, configuration error, or hardware issue) should still be identified and resolved.
1.3.1 TCO Parameters Not Received – K-Line and FMS Available
Situation: K-Line is active, FMS is available, but TCO parameters are not arriving.
Cause: K-Line is the primary source for TCO. The device will not fall back to FMS while K-Line is enabled, even if K-Line is not delivering data.
Resolution:
1. Investigate and fix the K-Line connection issue if possible.
2. If you need TCO parameters to come from FMS immediately, disable K-Line TCO mode in the device configuration.
3. FMS becomes the active TCO source once K-Line is disabled.
Note: Re-enable K-Line after the underlying issue is resolved to restore the intended configuration.
1.3.2 TCO Parameters Not Received – K-Line, Tacho Read, and FMS All Available
Situation: All three sources are connected and enabled, but TCO parameters are not arriving.
Cause: K-Line is still the priority source for TCO. A problem with K-Line prevents data from being received, and no automatic fallback occurs.
Resolution:
1. Investigate and fix the K-Line issue if possible.
2. To receive TCO parameters from Tacho Read instead, disable K-Line TCO mode in the device configuration:
3. Tacho Read becomes the active TCO source.
4. If Tacho Read also has issues, disable it as well — FMS will then serve as the TCO source:
Note: Re-enable K-Line after the underlying issue is resolved to restore the intended configuration.
1.3.3 TCO_CAN Parameters Not Received – All Sources Available
Situation: K-Line, Tacho Read, and FMS are all active, but TCO_CAN parameters are not arriving.
Cause: K-Line does not provide TCO_CAN data. Tacho Read is the priority source for TCO_CAN and has an issue. The device will not fall back to FMS automatically.
Resolution:
1. Investigate and fix the Tacho Read issue if possible.
2. To receive TCO_CAN parameters from FMS instead, disable Tacho Read mode in the device configuration:
3. FMS becomes the active TCO_CAN source.
Note: Re-enable Tachoread after the underlying issue is resolved to restore the intended configuration.