i have had install for downloading firmware esp8266.
ordinary tutorial said that we should connect rx to tx, tx to rx at first.
and then after install, many tutorial said using esp8266 to necessary connecting tx to 2, rx to ~3
so my question is… can i connect rx to tx, tx to rx without upward setting?
Perhaps you need to describe what you wish to do.
Sounds like OP is trying to program an ESP via an Arduino, in which case indeed it's an unusual tx/tx and rx/rx connection (don't forget the level shifting on tx).
And that is my point. It sounds like he is trying to do something, but he hasn't explained what it is and on that account, I am not sure he actually knows either.
What I'm really curious about is what an "upward setting" could possibly be.
Oh, yes of course, it has to be. How silly of me to not think of that.
Now whether the OP needs it depends on how it's all connected exactly.
This thread is going sideways....
Being new you probably don't realize those of us reading and trying to help don't know what pins on what device you are referring to. We know one is the ESP8266 but you did not specify the other. Nor did you state your goal. Stating the goal is very important because you may have started down the wrong path but we cannot help if we don't know the goal.
For most questions in these forums, "the devil is in the details" meaning without the details we cannot help you and if we tried we might lead you astray.
So try writing your post again (or edit it) but before you post it ask yourself..... If you only had the written details, would you understand the whole problem?
So try writing your post again (or edit it)
Note: Do not start another post - that will only cause trouble.
You may edit your original post using the "More..." and then "Modify" option at the bottom right of that post.
Or you can add to the end of this conversation to explain what it is you are trying to do.
But until you do that, there is no way we can help you effectively.
Best just a new post at the end. Otherwise I for one simply won’t see it.