USB to RS232 Adapter

Hello everyone!!

"I built an adapter a long time ago, following instructions from this forum (using a MAX232 chip), and it works perfectly! Then I got a new laptop and bought a USB adapter (from Digitus) that works flawlessly in my old Passat 1Z, but not in another Passat from 1998..."
Therefore, my question, after not really finding what I was looking for in the forum:
Is there a USB-to-RS232 adapter or kit available now that actually works (at a reasonable price, compared to a new diagnostic cable), or would it be better to switch to a new USB diagnostic adapter?

Thanks in advance, friends.

hello

That's probably due to the lack of power supply for the MAX232 chip...

It is generally powered from the vehicle's battery or a separate power supply.
if the USB adapter no longer has that feature, and if the interface on the other vehicle has also been cut, then nothing more can be done .
(It's possible that your USB port on the laptop is not providing the full 5V/500mA output due to power-saving reasons!)

Please measure the voltages on the MAX232 when it's connected to the serial port and when it's connected to the USB adapter.
It is possible that the power supply can be enabled in the laptop's BIOS.
Alternatively, you can use a USB hub with an external power supply, which will then provide power to the USB adapter (if it's a USB-to-serial adapter).

In the worst-case scenario, you may need to resort to an external power supply for the MAX232.

Good luck!

Hello,

USB to RS232 interface converters are always problematic. First, it adds additional latency to the transmission protocol. Second, it's possible that the USB to RS232 adapter doesn't support all the necessary baud rates.

Therefore, I advise against using such solutions, and that's why we don't offer USB to RS232 interface converters in our store.
A diagnostic adapter with a USB interface that does not emulate a virtual serial port would be the appropriate hardware. The link is, for example, below in my posting signature, but there is also a significantly cheaper KKL version without CAN-Bus support.

"Regarding the item: You can find similar junk at auction houses; it's essentially an RS232 adapter with a built-in RS232 to USB interface converter chip." Okay, so it's the same as your non-working solution in green. -> Same problems with specific control units.

Best regards, Rainer.