You will need at least minimum:
1 Launch Ball Button
1 Coin in Button
1 Start Button
1 Exit Button
2 Flipper Buttons
Other buttons to consider:
2 MagnaSave Buttons for games with MagnaSave or other game options
1 Extra Ball Button
But you can add more. It ́s a personal preference if you want to install more
Use a controller board that connects to the USB port.
The nudge card you can buy from Nanotech includes inputs for buttons and coin door switches.
You could use a keyboard interface like the IPAC - see BYOAC
The are several VPin Bards out there. Tested some of them and the first thing i can say is: DON ́T BUY THE VIRTUAPIN CRAP! They don ́t work! Are heavily overpriced and the support is like 0!
So which board should i use? This depends on some things. Like do you want to use DOF or not? You want to have Analog Plunger and Analog Nudging? Etc. Here are some Boards which will work for a Vpin
This depends where you live. The Pincontrol can be ordered as example here: https://vpin-shop.com/
The Pinscape software/firmware for kl25z developmental boards
this is DIY solutions and you have to decide on which parts you want to use etc.
if you want to know more about pinscape check https://os.mbed.com/users/mjr/code/Pinscape_Controller/wiki/Homepage
http://mjrnet.org/pinscape/BuildGuideV2/BuildGuide.php?print=go#kl25zSetup
https://os.mbed.com/platforms/KL25Z/
https://vpin-shop.com/vpinshop/toys/controller/pinin1/