Surely creating them from a simple microcontroller will be impossible! Not according to [techtoys], who has created an Arduino shield that creates an HDMI output from an SPI control input.

This means a single analog input of the microcontroller is shared among all the input channels (except the 3-axis accelerometer). Four additional microcontroller pins choose which channel to read.

Intel's Curie-based Arduino 101 Programmable Microcontroller development board goes under the microscope today to see exactly what it brings to the table.