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Connected Logger Data Upload Process

This page outlines how data files generated by the Connected Logger (CL) are handled during upload to Spoke Zone. It explains the transformation of data during the upload and why the data file size observed on Spoke Zone does not reflect the data usage on the Connected Logger.

Data Format on Connected Logger

The Connected Logger compresses its logged CAN data into a compact format of 14 bytes per record, with the following structure:

FieldSizeDescription
Data8 bytesLogged CAN data
DLC1 byteData Length Code
Time1 byteTimestamp (compressed)
CAN ID4 bytesCAN Identifier

Decompression During Upload

When uploading to Spoke Zone, the data is decompressed to a 20-byte format. For example:

  • The 1 byte Time field is expanded to 4 bytes.
  • Other fields are expanded as needed for full interpretation and usability in Spoke Zone.

This results in a data size increase of approximately 1MB → 1.41MB after conversion.

Upload Behavior

  • The Connected Logger has a 1MB upload size limit per request.
  • Due to the decompression, 1MB of logged data becomes 1.41MB after conversion.
  • As a result, the logger splits the data into 2 separate data files:
    • 1MB data file upload
    • 0.41MB data file upload

Decompressed Data Files

  • Once the data files are uploaded and fully decompressed, the data is then converted and stored in a .trc file format on Spoke Zone.
    • 1MB uploaded data file ≈ 3.7MB in the final .trc file format.

Upload Size Limitation

  • The 1MB maximum upload size is enforced because uploads larger than 1MB cause issues over LTE.
  • This is a hardware limitation of the Connected Logger.
  • Keeping upload packets within this threshold ensures reliable and consistent data transmission.

Summary

StageSize Approximation
Logged Data on CL1MB
After Decompression~1.41MB
Data Files2 (split at 1MB)
Final .trc file conversion on Spoke ZoneFile 1: ~3.7MB
File 2: ~1.52MB

Key takeaways:

  • Data File size seen in Spoke Zone includes file format conversion overhead and should not be used to infer cellular data consumption by the Connected Logger.
  • The data usage on the Connected Logger itself remains constrained to the decompressed format.