Default [Q] API for precisely modifying shutter speed, ISO, and aperture as exactly as I want

For the research purpose, I need to be able to control the shutter speed precisely without affecting or changing the ISO or the aperture. The shutter speed needs to vary from 10ms to 2000ms, with a step of 10ms. So that means there needs to be 200 different options for shutter speed, and so far the best apps for android phone just offer a few, and still they cannot keep the values of the aperture and the ISO the same in all images. I really wish that they can make the app in a way that I can plug in number for my shutter speed, ISO and aperture, and they have to maintain the same values no matter when or where I take a photo; for instance 1.27 seconds for exposure time, f/1.42 for aperture, 800 for ISO. I've been thinking about program my own app, but I have no idea how to start. I don't even know if it is possible to program an app that can really allow us to plug in numbers for the shutter speed, ISO, and aperture precisely in millisecond. Is there any idea?