Assistant Telematics: AVT20

Hi,

I’m testing an Assistant Telematics AVT20 (And AVT40) device which communicates using the hyn600 protocol on port 5258.

The device connects successfully and is shown in the Traccar portal, but I’m facing multiple issues:

1. Traccar frequently disconnects the device with:
   Adjusted frame length exceeds 1024: 13359 - TooLongFrameException

According to the protocol documentation, the AVT20 can send large data frames
(e.g. buffered / historical or extended data messages).

1. Some decoded messages contain an invalid device time, for example:
   0850-05-06 14:29:36

This results in database errors when storing positions.

1. The device identifier (IMEI) is decoded incorrectly.
   In the Traccar portal the device is shown with ID:
   60a4c0816342802

However, the actual IMEI of the device should be:
861076082252402

Despite these issues, Traccar sometimes decodes valid positions correctly.

Examples of raw messages received:

Login / short status message:
2d5250543a0022560a4c081634280222030201000000000007ea041e0b0822019e23

Large data message (causes TooLongFrameException):
2b5250543a0068560a4c081634280222030201000000011e0300000001ff01030100000000003c0329f6ec00644e9b07ea05060e29290d11000700cc000881500006e10d18000004a504d02200000000000000000000000000000000000007ea05060e2929046423

ACK / ASCII-type message:
2b41434b3a0026560a4c081634280222303330322c5349532c2c302c07ea041e0b0d3b01ab23

Questions:

• Does Traccar support hyn600 messages larger than 1024 bytes, or should the frame decoder be adjusted?
• Is the hyn600 IMEI decoding implemented correctly for AVT20 devices, or is a different field/format expected?
• Has anyone successfully integrated the Assistant Telematics AVT20 with Traccar?

Thanks in advance.

If needed i can't send the protocol documentation of the AVT20 and AVT50.,

Does your device actually send messages longer than 1024 bytes? To me it seems like maybe some messages are simply not supported correctly.

“Confirmed by logs: all received hyn600 packets are well below 1024 bytes; the reported size of 13359 is a result of incorrect frame length decoding, not actual large messages.
The incorrect IMEI appears to be caused by misaligned field decoding (BCD vs ASCII / offset), likely related to the same issue.”

Do you have documentation and full logs?

The protocol PDF of the AVT20 https://drive.google.com/file/d/1LciUO7XxdgsLTpM6K6jH1osh1CgBFmGo/view?usp=sharing
The protocol PDF of the AVT50 https://drive.google.com/file/d/163TxbTvGVAmGn5gO9eKCiaTmOpi2J658/view?usp=sharing
Log file: https://drive.google.com/file/d/1p5fFo5SaF2ifZ_2ohrfkZa8gJXYl4bdd/view?usp=sharing
I'm not sure if the log data is OK. I did some change of settings in the tracker with and withoud ACK. If needed i can create later a cleaner log file.

Can you please separate log sessions by device protocol type.

In this log is only the AVT20.