Changing Things Up with a Coin Acceptor Serial Adapter

Davide Gironi has an NRI G-13.mft coin acceptor unit from Crane, which according to him, is highly secure and versatile. It can be programmed using Crane's software and has DIP switches, but no UART interface. It does, however, have machine test I/O pins that can be used to track coin inputs.

This interface consists of six channels that are pulled low from their 3.5V state, depending on which euro coin is inserted. These inputs can also be used to inhibit accepting certain coins by setting the voltage to 1V, as opposed to the standard 3.5V, though this wasn't needed for the project. The setup forms a rudimentary parallel interface, but Gironi instead wanted a serial interface that he could pipe to his computer, outputting numbers on a terminal program.

To accomplish this, he created an adapter that takes coin acceptor signals, and translates them to serial using an ATmega8 microcontroller and a CP2102 UART to USB adapter. The board was constructed using a PCBA service, and while it took him three prototypes to get it right, he notes that he’s not a pro at PCB design, but had to start somewhere.

Code, schematics, and files are available for download toward the end of Gironi's blog post if you’d like to examine things more closely.

As for “starting somewhere” with PCB design, I couldn’t agree more. Here’s my attempt at an ATtiny85 blinkie PCB as a sort of “Hello World.”