This product is no longer available in our store.This ADkey brick is based on VOLTAGE DIVIDER method. It use 1 AD port to detect 5 keys' input. Divider resistance ladder are built by: 0Ω,75Ω,330Ω,1K5Ω,4K7Ω,1K Corresponding output levels are 5V,4.6V,3.75V,2V,0.88v, 10% expected error exisits due to resistor precision and Output voltage.DocumentsPlease visit our wiki page for more info about this product. It will be appreciated if you can help us improve the documents, add more demo code or tutorials. For technical support, please post your questions to our forum.Please refer to here for more details.