Is it possible to figure out how a mobile credit card reader, like Square, works?
Is it the same as the more popular Veriphone terminals that abound?
The problem is, that I am buying a Square like device from a supplier in China, and I want him to supply me a trustworthy device. I don't know how that will happen, without me knowing exactly what data he is transmitting from the app itself, as well as from the hardware of the device.
hence:
Circuit diagram for credit card readers please?