So, this is the first prototype using the better ADNS-9500 mouse sensor.
Few months have gone by now mostly because I have done everything I could think of, asked around, trying to solve the issue I had. I have actually thought this could be the issue a few times, but what can one do. The problem I had was that whatever I did, I couldn't get any motion data. The SPI worked, as I could get product id and such, but when I moved the sensor, I got nothing. As you can see in the image to the left, I have highlighted the component that is to blame for it all. This tiny, 1.5mm MOSFET wasn't properly connected (either not soldered properly, or damaged during soldering), and thus the Laser didn't get any voltage, and thus the sensor couldn't detect any motion. This is all solved now, in another prototype I've build, build like the one in the image, but using a similar MOSFET and this SOT23 to DIP Adapter.
So now, finally, the fun starts! It feels like a heavy weight has been lifted, and I can now finally continue with this project! I've actually started with the coding already and even started to create graphs based on the motion data I get...
More images and progress will follow...