Tool/software:
1.Question describtion
After connecting the PC to the DUT via an RS232 cable, it can print logs but cannot execute commands.
2.Analysis Process
I connected the TTL-to-USB adapter board via jumper wires to the MCU's UART serial port. At this point, the PC host computer can both print logs and write commands. However, when connected to the PC via an RS232 chip, it cannot write commands.
3.Waveform
Figure 1 shows the waveform corresponding to the log printed during the power-up process. The logic levels of the RS232 TX pin are normal, while the RX pin levels are abnormal, not within the ~3V to ~15V range.
Figure 1 shows the steady-state condition after power-up.
4.Connection Diagram
Figure 3 shows the RS232 schematic diagram.
5.RS232 SCH
Figure 4 shows the connection diagram.
6.uart log
Figure 5 shows that after printing the log to the shell, commands cannot be written.
