VE.Direct: sometimes the end sign from hex frames is wrong

[SW-Niko]

What happened?

The hex frame end sign is normally 0x0A ('\n') but sometimes we get 0xFE from the serial interface _vedirectSerial->read().
Example: ": A 0 0 0 2 0 0 0 1 4 8 fe"
The hex message and the checksum are fine. Just the end sign is wrong.

I assume this is not a transmission fault because I logged the data from 2 solar charger and 1 smart shunt over one week.
Smart shunt: No faults
Solar charger: 5 text frame checksum faults and 8 hex frame end sign faults (always 0xFE instead of 0x0A)

To Reproduce Bug

Do a long time logging of the VE.Direct interface

Expected Behavior

Transmission faults must be random.

Install Method

Self-Compiled

What git-hash/version of OpenDTU-OnBattery?

3463b14

What firmware variant (PIO Environment)?

generic_esp32s3_usb

Relevant log/trace output

Special logging
17:48:28.671 > [VE.Direct MPPT 7/17] ------------Frame Handler--------------
17:48:28.887 > [VE.Direct MPPT 7/17] Frames: 71177, Frames containing V-Field: 71176, Frames per Data-Set: 1
17:48:28.990 > [VE.Direct MPPT 7/17] Communication starts: 1, Start frames lost min: 1, Start frames lost max: 1 
17:48:29.041 > [VE.Direct MPPT 7/17] Checksum faults: 1, More then 500ms fault: 1, Start checksum: 0
17:48:29.100 > [VE.Direct MPPT 7/17] Text buffer overflow faults: 0, Value buffer overflow faults: 0
17:48:29.147 > [VE.Direct MPPT 7/17] Hex checksum faults: 20, Hex buffer overflow faults: 0, Hex Hex faults: 2
17:48:29.197 > [VE.Direct MPPT 7/17] Last fault: From hex to hex
17:48:29.299 > [VE.Direct MPPT 7/17] serial input (208 Bytes):
17:48:29.501 > [VE.Direct MPPT 7/17]  :  A  0  3  2  0  0  0  F  F  7  F  A  A 0a  :
17:48:29.552 > [VE.Direct MPPT 7/17]  A  2  7  2  0  0  0  0  0  0  0  0  0  0  0  0
17:48:29.598 > [VE.Direct MPPT 7/17]  4 0a  :  A  D  5  E  D  0  0  3  0  0  A  4  F
17:48:29.646 > [VE.Direct MPPT 7/17] 0a  :  A  5  0  1  0  0  0  0  0  0  0  0  0  0
17:48:29.693 > [VE.Direct MPPT 7/17]  0  0  0  0  0  0  0  0  0  0  0  3  3  0  A  2
17:48:29.739 > [VE.Direct MPPT 7/17]  E  0  A  0  0  0  0  0  0  0  0  0  0  0  0  0
17:48:29.787 > [VE.Direct MPPT 7/17]  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
17:48:29.830 > [VE.Direct MPPT 7/17]  0  0  0  0  0  5  D  0  4  6  C  0  0  A  9 0a
17:48:29.878 > [VE.Direct MPPT 7/17]  :  A  4  F  1  0  0  0  0  1  0  0  0  0  0  0		Historische Daten
17:48:29.925 > [VE.Direct MPPT 7/17]  0  0  0  0  5  D  7  E  0  0  0  0  5  D  7  E
17:48:29.976 > [VE.Direct MPPT 7/17]  0  0  0  0  8  6  1  1  C  3  0  B  1  E  2  2
17:48:30.022 > [VE.Direct MPPT 7/17]  0  5  F  F  F  F  F  F  F  F  F  F  F  F  F  F
17:48:30.069 > [VE.Direct MPPT 7/17]  F  F  F  F  F  F  F  F  F  F  F  F  9  8 fe  :		fe anstatt 0a

Anything else?

On my system the issue pop up 2 times a day. Not really a problem.

I was not able to find the root cause of the problem. Maybe a bug on Victron side or on the ESP32 serial driver.

Please confirm the following

• I believe this issue is a bug that affects all users of OpenDTU-OnBattery, not something specific to my installation.
• I have already searched for relevant existing issues and discussions before opening this report.
• I have updated the title field above with a concise description.
• I have double checked that my inverter does not contain a W in the model name (like HMS-xxxW) as they are not supported.