VAGCOM Adapter: All Generations Compatible?

Hello.

I want to design a simple, DIY universal adapter for VAGCOM.
- the ability to switch between all conceivable configurations (L + K-line, 1 x K, 2 x K).
- Separate indicator LEDs for both K-lines, allowing you to see in a dialogue, for example, that the engine control unit (ECU) is responding on K-line 1, while the alarm system is responding on K-line 2, etc.

However, I first need some input to determine whether the rectifier control for 2 K-lines in the VAGCOM adapter (see construction proposal 1.1 in the diagnostic technical article) actually works in practice.

Who has relevant experience?

Hello Ulf,
Basically, I would build the L/K2 level in the same way as the K(1) level.
In K-L (and K) operation, this second stage receives its input signal from RTS, and the return path must terminate in the vacuum.
In a K1-K2 configuration, the second stage receives its signal from TxD (just like the first stage), and the return lines of both stages must be interconnected.
Whether you use diode logic (rectifier) or parallel 'open collector' output stages is a matter of personal preference. The latter works fine in my adapter without any problems, but I also tried the diode circuit on the 'standard' K-line – and it had no negative effects!

Best regards, Rudi.

Rudi wrote:

I also once tried the diode grave on the 'standard' K-line -> no negative effects!

Hi Rudi,

Okay, so already "a half of practical experience" .

In an initial preliminary design, the 2K-diode grave now consists of 3 LEDs (for TXD, RXD K1, and RXD K2) and 4 normal diodes - so a total of 7 pieces. It looks nice in the schematic diagram .

However, this means that the RXD LED on the COM port will no longer function.

I'll probably build this component based on the Opto-2.4, but with a slew rate enhancer on the RXD line, just in case VAGCOM ever uses higher baud rates in the future.

To save switch contacts, only pin 15 of the OBD connector is switched to either the standard L-amplifier or the second K-output of the (LED) diode matrix – one switching action is sufficient.
In cars with a single K-line and without an L-line, the L-signal simply goes nowhere.