My new Nano has arrived, but the situation is still not optimistic. This time sending data seems to be okay, but receiving fails.
I connected the wires refer to the wiring diagram below and connected Nano to Arduino.A side is Nano and B side is Arduino
The Arduino program is the same as before, returning the received data.The result is shown in the figure, and Nano is stuck and cannot exit minicom.
Then I connected the Nano to the laptop via a UART to USB converter.
Nano sends data smoothly：
But for receiving, only a few data can be received occasionally. The part underlined in red is the data sent to nano via laptop：
Same result for the program I wrote：
The red underlined is the data sent by Nano. But Nano cannot accept data.