Vending machine sales process
①The user puts the currency into the coin slot, and the currency recognizer recognizes the deposited currency;
②The controller provides the saleable information of the product to the user through the selection button indicator according to the amount, and the user independently selects the product he wants to buy;
③The user presses the button corresponding to the selected product, and the controller receives the information transmitted by the button, drives the corresponding component, and sells the product selected by the user to the retrieval port;
④If there is enough balance, you can continue to purchase. Within 15 seconds, the vending machine will automatically find change or the user presses the return button to withdraw the change.
⑤ Withdraw Zcoin from the refund port to complete the transaction.