difference between USB TTL adapter and UNO Clone

I am not sure if I understand everything in your post, but if you want to abuse the Uno as Serial-to-TTL adapter the sketch in ATmega328p must not have Serial.begin

No,

its just the other way.

the hole thing is working with the abused uno.

Now I want to replace the uno with an normal USB TTL converter, to simplify the hardware.

But the software on computer does not 'speak' to it like to the Uno (I see the RX LED blinking). The TTL adapter keeps beeing dark.

CarstenE:
No,

its just the other way.

the hole thing is working with the abused uno.

Now I want to replace the uno with an normal USB TTL converter, to simplify the hardware.

But the software on computer does not 'speak' to it like to the Uno (I see the RX LED blinking). The TTL adapter keeps beeing dark.

the adapter has CH340? did you install the driver?

Yes. It has CH340. Driver is installed. It seems to work ( I tested it by connecting RX and TX, and send some lines with the Serielmonitor in the Arduino IDE)

The only question is, there must be a little difference in the behavior, so that the software can divide between the uno and the adapter.

CarstenE:
The only question is, there must be a little difference in the behavior, so that the software can divide between the uno and the adapter.

With your Uno on Serial2 you connect Rx to Rx but with your USB-TTL on Serial3 you connect Rx to Tx. If you replace the Uno with a USB-TTL adapter it must be connected Rx to Tx like on Serial3

Have you tried the USB-TTL adapter that you want to use on Serial2 in place of the adapter on Serial3?

If that does not solve the problem then you need to draw a simple diagram that clearlt labels all the connections in the working system and in the non-working system. Then post a photo of the diagram - see this Simple Image Guide

...R

I did all the things you suggested.

but it isnt working. The RX Led doesnt show any transmission if the adapter is connected

See some posts forward.

CarstenE:
I did all the things you suggested.

but it isnt working. The RX Led doesnt show any transmission if the adapter is connected

and swapping the adapters?

the adapter that is connected to serial2 gets no connection to the computer. I does not matter which one I use. ( I also changed the comports in the Sotware so that the address is correct)

CarstenE:
the adapter that is connected to serial2 gets no connection to the computer. I does not matter which one I use. ( I also changed the comports in the Sotware so that the address is correct)

then it could be anything. try to swap the cables, the USB ports, ...

I think I tested every possibility of change. Always the same result.

The software detects that there is no arduino at the choosen com port and does not work.

Funny.

CarstenE:
I think I tested every possibility of change. Always the same result.

The software detects that there is no arduino at the choosen com port and does not work.

Funny.

there is no Arduino. only the USB adapter.

so it is still Serial2 not working with any wire, adapter, cable, USB socket?

No. the picture shows that it is working, if the adapter is an uno.

CarstenE:
Sorry. First time. wrong rotation.

It is still wrong :slight_smile:

CarstenE:
the adapter that is connected to serial2 gets no connection to the computer. I does not matter which one I use. ( I also changed the comports in the Sotware so that the address is correct)

Have you tried what I suggested - to check if the "new" adapter works with Serial3 ?

Have you tried changing the order in which you connect the USB devices? On Linux the order of connection determines the serial port names on the PC. And don't expect the USB TTL adapter to appear as the same COM port as the Uno.

...R

New picture right orientation.

Yes, I checked this. The 'new' adapter works at Serial3.

Yes and I checked all ports and every configuration every time, so that the software would do the right things.

CarstenE:
Yes, I checked this. The 'new' adapter works at Serial3.

Yes and I checked all ports and every configuration every time, so that the software would do the right things.

on the picture you have ground wire only at Serial 2. how is it in reality?

Sorry I forgot this.
Every component has its own connection to ground of the mega.

Have you considered that the problem may be within the PC - what software is trying to communicate with the Arduino?

...R