VAGCOM: Fast-Sync Feature?

Hello.

I know this topic has been discussed before. But maybe someone knows more about it now than they did back then...

During my adapter experiments, I once shorted TXD and RXD, which, in my opinion, simulated the "ideal" adapter.
He was correctly recognized by VAGCOM, but still displayed as...
"Fast Sync Compatible: NO"
categorized.

What more should a "Yes" adapter be able to do besides sending the data back as an immediate echo without any delay, meaning essentially infinitely fast ?

Hello Ulf,

I was just playing around with a D-Sub 9 adapter.
Result: Connecting pin 3 (TxD) to pin 1 (DCD) during the...
Adapter test result: Fast-Synch Compatible: YES.

Tested with VAG-COM 0.81a and a powered adapter (although without a control unit; I didn't have one handy at the time).

Best regards, Rudi.

Rudi wrote:

A connection from pin 3 (TxD) to pin 1 (DCD) will cause... Adapter test for the output: Fast-Synch Compatible: YES.

Hi Rudi,

aha, very interesting!

Does anyone here know of a source or link where I can learn more about the function of the individual pins of a COM port?

Hello Ulf,
DCD (Data Carrier Detect) was/is used to determine whether the remote device is connected (typically connected to the DTR - Data Terminal Ready - output of the remote device).
Otherwise, the DCD pin is an input that a program can evaluate and use in any way it sees fit.
By the way, you also get the 'Fast-Synch = Yes' result if DCD is connected to pin 2 (RxD) (which is not surprising, since what goes out through TxD comes back through RxD).
Whether and what impact 'Fast-Sync' will have remains to be seen (perhaps faster logging?).
I suspect that Uwe Ross ensured a certain timing behavior in his adapters, and that the software recognizes this, allowing it to assume certain preconditions.

Best regards, Rudi.

Hi Ulf,

You can find a lot of information about serial interfaces, for example, here.

http://www.beyondlogic.org/serial/serial.pdf

Olli.

olli wrote:

You can find a lot of information about serial interfaces, for example, here.

Hi Olli,

Thanks for the information, I've already downloaded it... but do you happen to know of anything similar in German?
I'm not very good at English .http://www.beyondlogic.org/serial/serial.pdf{MARKER}

Hi,

There is also information available in German, but I haven't found anything as comprehensive there; take a look under:

http://www.e-ntwicklung.de/skripte/serielle_schnittstelle.pdf

Maybe that's enough.

Olli.

olli wrote:

check out under

Maybe that's enough

Hi Olli,

Great, I think that will help me a lot.

Thank you! http://www.e-ntwicklung.de/skripte/serielle_schnittstelle.pdf

Okay, so the connection between pins 1 and 3 on the RS-232 interface seems to almost work for synchronization during the adapter test, but otherwise, I don't see any difference with my problem (issue #1). When I set the parameters in the options to their default values, I experience the same issues as I do without 'fast sync.' The communication isn't even faster. It would have been a shame if it had worked!

Hello Jörg,
Could you please connect point 1 and point 2? For the adapter test, it does the following:
no difference, because the data sent to TxD immediately returns to RxD.
It's possible that VAG_COM behaves differently when the data from the control unit is sent to DCD.

Best regards, Rudi.

@rudi

I'll give it a try!

Hello.

After reading about COM ports, I'm wondering if it makes sense to send data signals on "status lines" like DCD, etc.
Because then the COM port would be confused by the timing of the transmitted bits, in a manner like this: "the other end is ready for communication - not ready for communication - ready for communication..."

Wouldn't it be more sensible to also provide a status signal, such as DTR (high during the entire communication), to the status inputs?

Okay, that's enough theoretical rambling – I'll probably try it out myself this weekend.

@ulf

'The handshake lines are the only ones you can directly access from Windows. So, if Mr. Ross programmed things properly, then you're right. However, it seems that might not always be the case. See my post above. Also, there should be a control line from the STG (Steuergerät - control unit) for it to work properly. If such a line existed, it would also help synchronize the bit length differences that cause problems with many older STGs.'

Hi everyone,

I just tried out the actual near-synchronous behavior.

Please provide the German text you would like me to translate.
As a "YES" for Fast Synch Compatibility, an adapter is actually only recognized when the data stream is "copied" to the TXD or RXD pin after DCD --> insert a bridge.
Connect RTS or DTR with DCD --> NO

I then "only" connected TXD with DCD because there is "less activity" there (only transmitted data instead of transmitted and received data).

2.
The bridge failed to provide any progress in the communication with my tractor; in fact, on one occasion, measurement block 4 could not be opened, even though the communication was stable (LEDs 2 and 3 were blinking normally).

So, I took the bridge out again and am now using the NO-adapter again...

Well, it was a nice attempt, and I learned something new.
Among other things, I only have a superficial understanding of VAGCOM, at best .

@all

Okay, I can only confirm Ulf's observations regarding the increasingly insecure communication in my specific case.
The connection between pins 1 and 3 on the RS232 interface is more stable than the connection between pins 1 and 2.
'I'm experiencing an issue where I can no longer access the ABS control unit. The airbag system sometimes works, sometimes it doesn't. I can always access the engine control unit, but it has problems displaying some data groups correctly while driving. Additionally, the communication often becomes intermittent.'
Communication is seamless between modules 1 and 3; all measurement groups are displayed correctly, and all control units can be accessed without issues.
All results were tested using my communication parameters, which I have optimized in the settings.
That means either Mr. Ross installed something else in his adapter, or Fast Sync has hardly any effect!

ps: brrrrr, it was so cold! 16 degrees below zero.