yes it's probably best to build a breakout board and use a coin mech to add credits to your dongle card and on the break out board have the payout hopper control and ball return counter.and mars coin mech connected to the breakout board to send the correct amount of pulses to your dongle.Why re-invent the wheel,you have alreay done the hard work.This should be a simple task as i have already built a coin to token change machine as i said above.