After inserting the money and selecting their size, customers were surprised to see a video start playing on a 22” HD display fitted into the plexiglass. They watched shocking scenes from textile factories of women and children sewing without a break, paid only 13 cents per hour for working under life-threatening conditions.
After 20 seconds, an option appeared on the touch-screen display to either continue with the purchase and buy the t-shirt or donate the 2€ to Fashion Revolution instead.
Project was based on small PC connected to Arduino, which was connected to the vending machine. The vending machine was running on MDB protocol, developed by coca-cola more than 30 years ago.
Tricky part was the 9 bit data frame. Most of protocols run on 8 bit frame, fortunately AVR microcontrollers have access to the 9th bit through shift registers. Additional tweaks in arduino standard library allowed to gain control over vending machine.