The apm connects to PC, make sure you have installed the Misson Planner, and select the right port and baud rate.
You can download Misson Planner from here,
For example, my computer’s port is COM85, maybe your port is not same with me. Maybe COM3 or other.
Make sure you select the right COM port, and the baud rate is 115200.
Note, the port cannot be seleted with AUTO or other. If you use USB to connect, baud rate should select 115200 , not other.
If your PC cannot recognize the port. First check your USB line, make sure it can work well. Second if the issue also happened, you should install the PC’ driver for the APM.
YOU can download it to install it on your PC. Some WIN7 cannot install it sucessufully, maybe you can change other PC system, i recommend the WIN10 system.
If your driver is like this, you should install the driver to your PC.
If your PC do not have the port, you should change other USB line.