title: USB light sensor (ALS) product or implementation?
body: <p>I've been looking for a way to retrofit light sensors to my laptops which lack one.</p>
  
  <p>The best specification I've found so far is in the ACPI 3b spec, section 9.2, that details how such a sensor would be implemented. I assume Linux would also follow the spec.</p>
  
  <p>My first question: is there such a device on the market? A small USB dongle that measures light and provides that to the OS. I already have a Spyder i1 that can do this, but it's overkill and large.</p>
  
  <p>Second question: would it be possible to implement this using Arduino and V-USB? If yes, how would one approach the project?</p>
  
  <p>Is it even possible to do this via USB?</p>
  
  <p>Background: a small USB microcontroller and an LED can function decently as a light sensor by measuring LED capacitance, with no other external parts. This is well documented and also tested by myself.</p>