1. can automatically send and receive normally, which only shows that its own sending and receiving settings are correct. Need to check whether the setting of ARM2 103 is the same as that of the computer. Agree to the 4th floor, and see if the parity bit and the number of data bits correspond.
Second, the baud rate needs to be tested with an oscilloscope. Send a 0x55 to see the time taken by one bit, and calculate it to see if the baud rate is correct. Self-receiving is spontaneous, that is to say, the baud rate of the sender and the receiver is the same, and it is impossible to see whether the baud rate is correct, so there is no need to guess whether it is the baud rate. Test with practice.
Third, if the serial port height guide can also be spontaneous, all of the above are fine, so you should consider the communication circuit. This may happen if the power supply of your 232 communication chip is 3.3V and the capacitance around the chip is 0. 1uF. Try replacing four 0. 1uF chips with 1uF chips. 232 chips from different manufacturers will also be different. I've been in this situation. Try switching to a 5V power supply.
good luck