I want to install the previous Ardusub firmware. I clicked advanced settings to choose the custom firmware option. Although I downloaded the previous firmware file to my pc, it says that there is no firmware.
What should I do?
Are you sure you downloaded the correct file?
You can find the correct files here :
if you have pixhawk1 you must download https://firmware.ardupilot.org/Sub/stable/Pixhawk1/ardusub.apj (apj file)
if you have pixhawk4 you can download px4 files