import chisel3._

import chisel3.util._

// Problem:

//

// Implement a vending machine using 'when' states.

// 'nickel' is a 5 cent coin

// 'dime' is 10 cent coin

// 'sOk' is reached when there are coins totalling 20 cents or more in the machine.

// The vending machine should return to the 'sIdle' state from the 'sOk' state.

//

class VendingMachine extends Module {

val io = IO(new Bundle {

val nickel = Input(Bool())

val dime = Input(Bool())

val valid = Output(Bool())

})

val sIdle :: s5 :: s10 :: s15 :: sOk :: Nil = Enum(5)

val state = RegInit(sIdle)

when (state === sIdle) {

when (io.nickel) { state := s5 }

when (io.dime) { state := s10 }

}

when (state === s5) {

when (io.nickel) { state := s10 }

when (io.dime) { state := s15 }

}

when (state === s10) {

when (io.nickel) { state := s15 }

when (io.dime) { state := sOk }

}

when (state === s15) {

when (io.nickel) { state := sOk }

when (io.dime) { state := sOk }

}

when (state === sOk) {

state := sIdle

}

io.valid := (state === sOk)

}

object VendingMachineMain {

def main(args: Array[String]): Unit = {

chisel3.Driver.execute(Array("--target-dir", "generated/VendingMachine"), () => new VendingMachine)

}

}