RS232-MDB® (PC2MDB®) For

Easy Vending Machine Cashless Payment Design

A simple yet powerful way to connect the RS232 interface device including PC,PLC,Raspberry pi or Android board to the existing vending machine.and working as the slave cashless payment device.

How does the RS232-MDB work with the PC?
The RS232-MDB is connected with the existing vending machine to work as a cashless payment module. Complete almost all initialization and MDB protocol data exchange. The role of the PC is the payment collection terminal, as long as it is necessary to send simple instructions to the MDB box through the serial port to add the credit (swipe the card) to start the vend session, confirm the vend, and end the vend session.

(Raspberry Pi Version) For

Vending Machine Cashless Payment Design with Raspberry Pi

We provide an included plastic Housing that allows the MDB board to be plugged into the GPIO header of the Raspberry Pi board to assemble it together.

The assembled set is connected to the vending machine through the MDB harness, communicates through the MDB bus of the vending machine, and also supplies power to the MDB board at the same time from MDB bus. The MDB board will supply power to the Raspberry Pi through the GPIO bus. In this way, the Raspberry Pi does not need to be equipped with an additional power adapter.
The communication between the MDB board and the Raspberry Pi is through RXD and TXD on the GPIO bus.

About The RS232-MDB(PC2MDB) Adapter box

Smart cashless payment adapter box for vending machine!

Smart Designed RS232-MDB Adapter Box

The vending industry standard NAMA Multi-Drop Bus (MDB) may now be interfaced a PC to the existing mdb interface vending machine with the RS232-MDB. The RS232-MDB allows PC computer,android maini board, Raspberry pi, RS232 pos and all other RS232 controllers to be connected to the vending machine.Follow WAFERSTAR's quick use guide and send some simple and necessary instructions to realize cashless payment. It's easy to get started and complete the design.

Conforms to all NAMA MDB specification and is compatible with any MDB compliant vending machine. Hardware interface comes with cables,user's guide and user's protocol.

RS232-MDB(PC2MDB)'s Main Features

Happy to select and use our MDB box. It is very easy to start!

Smart VMC vending machine simulator

Smart VMC board with Dex interface for MDB cashless payment development!

Who will use this board?

1. Develop the vending machine mdb payment interface, including coin acceptor, bill acceptor or cashless payment device. Of couse, your target project must be MDB interface payment.It can also be an assistant for learning DEX interface and developing vending machine data management system.

2.Want to develop the vending machine management system, vending machine management server. For above project ,but you don't have a real vending machine and also that real vending machine is big size and heavy to move to the engineer office

How can we use this vmc board ?

Very simple to use. You just connect your MDB payment device, VMC will detect the mdb device . And you can pay through the mdb payment device and then select the goods, then VMC board will simulate to dispense the goods and end the order processing.

Letpos: Connect MDB payment device to Pulse vending machine

Smart payment module, compatible with MDB coin acceptor,bill acceptor and cashless card reader

Who will use this board?

1. Simple vending machine,for example,washing machine,water vending machine, it just has the pulse payment input , but want to connect a MDB card reader to it and pay with the cashless card.

2. It still can connect the pulse coin acceptor together to accept the payment.

How can we use this Letpos board ?

Very simple to use. Just attach the original pulse coin device to the LETPOS board, and also plug the MDB payment device,for example Nayax card reader to the Letpos board. Provide 24V power supply, and then the pulse output of the board can be connected to the pulse input port of the previous vending machine. And just a few simple setting with the price per pulse, Pulse width, Minimum price to start and so on.

MDB-SPY: Good VMC and MDB slave devices development sniffers tool

Monitor the MDB bus to learn MDB protocol, find out protocol errors, incompatibilities, timeouts!

Who will use this board?

1. When we do the integrations, software development of an MDB device or VMC etc is that there are “issues” with the data communication. We need check the MDB bus data to find out protocol errors, incompatibilities, timeouts

2. Want to know more in detail how the brand vending machine communication data.

How can we use this MDB-SPY ?

Very simple to use. Just plug it to the MDB bus and also connect it to the PC RS232 port. then use the PC serial tool to monitor the raw mdb data easily.

We Design, Manufacture and Sale

Hot-selling products from WAFERSTAR related to vending machines!

How the RS232-MDB Works? Play And Watch!

View RS232-MDB Demo Video

View VMC Video

View Letpos with Nayax card reader Video

View Letpos setup Video

View MDB-SPY with FuJi Vending machine Video

View MDB-SPY with Necta coffee vending machine Video

What Our Users Say’s

See what our happy Customer say about RS232-MDB. We are proud to have our users.

RS232-MDB and Relative product

We have a series of related products available!


COM Version

  • RS232 interface
  • Easy for cashless module design
  • Long-term application guarantee
  • Simple and Professional
  • Online Skype Service
Order Now

USB Version

  • Fully Compatible
  • FT232RL USB chip on board
  • Comprehensive USB driver support
  • Simple and Professional
  • Online Skype Service
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Raspbery Pi

Raspberry Pi Version

  • Plug on the Raspberry PI
  • Well-designed plastic case
  • Communicate through RXD and TXD on GPIO
  • Output DC5V for Raspberry PI
  • Online Skype Service
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For Vending machine design

  • Different from RS232-MDB
  • Simple, reliable and easy to use
  • Working as master MDB module
  • Simple and Professional
  • Online Skype Service
Order Now

Download the Files

Download the manual for RS232-MDB and MDB protocol

Download the manual for VMC, Good Cashless payment auxiliary development tool!

Frequently Questions and Answers

You can find the questions and answers of your interest here!

    MDB stands for "Multi-Drop Bus" and is a protocol developed by vending machine industry. The "Multi-drop Bus" (MDB) protocol is not compatible with the standard RS232 PC protocol and therefore a hardware and software interface is necessary.
    The RS232-MDB is a microprocessor controlled hardware interface with embedded firmware that converts the MDB protocol to an RS232 protocol and also performs the necessary voltage conversion.
    RS232-MDB also undertakes a lot of necessary real-time communication with the vending machine. This allows users to develop cashless payment devices very simply and quickly. There is no need to study too many communication protocols.
    The first purpose of purchasing this device is to develop a cashless payment device that can communicate with the vending machine, make payments, and allow dispensing the goods, so as to realize unattended automatic payment and sales.
    You can choose any RS232 device as a payment device, such as an existing POS machine (of course, you must have the ability to program on the POS machine, communicate with the RS232-MDB box according to the protocol and send and receive the data). You can also choose a computer, an Android motherboard, or a Raspberry Pi motherboard as a payment device. As long as it is a serial communication device.
    Next, you only need to use a simple serial port tool (Also can be provided by WAFERSTAR company) according to the instructions in the Quick User Guide, and then you can manually send data to pay and allow dispensing. You can be surprised to find that with the help of the RS232-MDB box. Realizing cashless payment is so simple.
    Of course, the hardware connection is relatively simple. A professional hardware engineer is not necessarily required. However, you need to have a professional software engineer to complete the subsequent software development work. At the same time, you also need to research and read the MDB standard protocol so that you can fully control the equipment and develop a higher quality software system.
    After purchasing WAFERSTAR's RS232-MDB, we will provide an easy-to-understand Quick user guide. A PC testing software will also be provided. In this way, after you prepare the motherboard and accessories, you can directly test and realize the cashless payment device. Such as add the credit value payment to the vending machine, approve the vend etc.
    Of course, if you need the source code of the PC test software, you need to purchase the SDK. The SDK includes more detailed and Quick-response technical support (this is the key point), two USB-to-serial adapters and the source code of the test tool software.
    After purchasing the SDK, our technical staff will assist you to understand the MDB protocol, analyze the errors in the receiving and sending of MDB commands, including subsequent understanding of the protocol. It is equivalent to a small amount of expense for you and one more technical guidance of the MDB protocol to help you quickly understand and complete the development.
    Normally, if your device has a RS232 port, you can directly choose the box with the RS232 interface. If your PLC or android board does not have a RS232 port, but only has a USB interface, you can choose the USB interface. Plug our USB box into your device, it will generate a virtual serial port on the device (need to install the necessary driver, our USB chip is FT232RL, you can directly search for the driver on GOOGLE, download and install).
    If you are a Raspberry Pi, you can directly purchase the Raspberry Pi version, then you can directly plug it into the Raspberry Pi motherboard and communicate through RXD and TXD on the GPIO bus. At the same time, our board will also provide the power supply to the Raspberry Pi through the VDD on the GPIO, so your Raspberry Pi does not need additional power supply.
    Sometimes, the interface on your motherboard may be a TTL serial port. We can also customize the characteristic TTL interface communication for you.

    In WAFERSTAR's online shop, there is an MDB-RS232 adapter. There is also an RS232-MDB adapter. Some people do not read the product description carefully, or are not sure what they need, it is easy to order mistakes. Please read the following carefully. If you are not sure, you can also contact us before ordering.
    MDB-RS232 is used to connect the MDB bill acceptor,coin validator,cashless payment device to computer. then you will design the Software that will run in the PC and work as the master main vending controller. For example,you develop the kiosk information machine. then you need to connect the MDB bill acceptor,coin validator to computer,but you don't know how to connect the MDB interface payment device to computer, because computer only has the RS232 port, no MDB port.then you need to order the MDB-RS232 adapter (MDB2PC Adapter ).
    RS232-MDB is used to connect the pc to existing vending machine.then you will need to design the Software that will run in the PC and work as the slave cashless payment device.and then you PC will work as a cashless payment device to vending machine. For example,you want to use the PC to give payment credit to existing vending machine, or if you want to make the internet connection to the vending machine and give credit to vending machine remotely, then you need to order the RS232-MDB adapter (PC2MDB adapter ).
    From the above description, it can be seen that in fact, RS232-MDB can be used as a cashless payment device and can be connected to the MDB-RS232 device. Here MDB-RS232 is directly connected to the PC as a host device. The RS232-MDB is a kind of slave payment device which is parallel to the Bill acceptor and coin validator at the same time.

  • I have understood the difference, what I need is RS232-MDB. Order Samples now! .........
  • Now I understand the difference between them, what I need is MDB-RS232. I want to continue to learn about MDB-RS232..........
  • Coin simulator can help you
        We have the MDB coin validator simulator,which can help you to connect the RS232 device to vending machine,but will simulate a coin validator.
        That means our converter will work with the vending machine as a coin validator,but the coin credit can be added through RS232 interface or just simple pulse input.
        An MDB Universal Satellite Device (USD) is a vending device which lacks customary credit acceptance peripherals. As such, a USD must rely on a host vending machine controller (VMC) to establish credit sufficient to perform a vend.
        There are three USD modes
        Mode 1: VMC is used to select items to be vended from the USD and the VMC contains all pricing information. The USD receives vend requests from the VMC and reports vend success or failure. (the USD is completely controlled by the VMC)
        Mode 2: The USD or the VMC may select items to be vended. The USD may have special requirements for price and/or selection ID display. In this case, the USD may issue a FUNDS request to retrieve this information. The USD must then issue a VEND request to gain approval from the VMC before a vend can take place. (The VMC is responsible for collecting payment and confirming the shipment. At the same time, you can select the goods on the VMC and USD)
        Mode 3: The USD selects items to be vended and has its own pricing information. The USD must issue an vend request to the VMC and gain approval before a vend can take place. (That is, the VMC is only responsible for collecting payments and confirming shipments.)
        Of course, when we are considering designing and using this extended USD interface and designing our application, we must first confirm that the VMC supports the USD interface. Because many vending machines on the market do not support it.
        Waferstar's USD-MDB provides such a converter, which converts the USD interface to the RS232 interface. At the same time, some necessary but tedious tasks were completed. Make the design of USD equipment easier.
    NAMA Releases MDB Version 4.3
        CHICAGO — August 22, 2019 — NAMA announced today the release of the latest version of the Multi-Drop Bus (MDB) standards – Version 4.3.
        This spring, NAMA VDI Task Force Chair Chris Lilly (Compass Group USA) appointed an ad hoc technical standards committee headed by Bob Ross (Ellenby Technologies, Inc.) with special assistance from Scott Hudis (Fawn Engineering Corp.), and Joe Simpkins (USA Technologies, Inc.) to implement revisions to MDB Version 4.2. Fifteen NAMA members volunteered to participate in this latest update, and significant contributions were also provided by the European Vending Association (EVA) with guidance from Vladimir Lopatin (Uvenco Group).
        “As VDI coordinator, I applaud the fine work of this committee under the skillful leadership of Chris Lilly, Bob Ross, and Vladimir Lopatin,” said Michael Kasavana, Ph.D., NAMA Endowed Professor Emeritus. “Committee members provided valuable input that impacts our industry tremendously. MDB Version 4.3 allows for a comprehensive treatment of cashless transactions across convenience services. The MDB standard has a long history of quality and reliability, and MDB Version 4.3 is built on the same proven principles,” he concluded.
        The MDB Version 4.2 standard had not been revised for eight years. MDB Version 4.3 is now available as a downloadable PDF on the NAMA website. Download your copy here. It is important to note that compared to the earlier version, MDB Version 4.3 revisions only appear in ‘Section 7 - Cashless Devices.’ The revised Section 7 is color coded to help clarify the changes. All other sections of MDB Version 4.3 remain identical to those of MDB 4.2.
    VMC simulator can help you
        1. You can use it to test the cashless payment device during development. For example, if you want to use the RS232-MDB box to develop a cashless payment system, you need to have a vending machine for testing. If you don't have or don't want to buy a vending machine that is bulky, heavy, expensive or even complicated to operate, and puts it in the office, you can buy our smart VMC board.
        2. It can work with coin validator,bill acceptor and cashless payment device.
        3. It can also be an assistant for learning DEX interface and developing vending machine data management system.
        Every vending machine has a VMC (vending machine control board) which performs all the transactional functions necessary to make a sale. These include coin counting, bill validation and credit and debit card acceptance. This information is gathered and translated to DEX format so that it can be accessed by the person in charge of managing that particular vending machine.
        This technology allows the data to be transferred remotely to a computer terminal or access on a handheld device while on a service visit. There are multiple programs out there from different companies that help manage this data and develop reports that are easy to read and utilize. These reports can help vending machine business owners or operators make profitable choices about products and routes.
        DEX technology captures information and reports generated that include product prices, total sales from cash, debit and credit, sale numbers for each product, the total amount of money held in the machine and other vital data. All of this information is essential for understanding if a particular vending machine is making money, which products to stock more of and what to do to increase profits overall.
        With such a large collection of information gathered with DEX technology, people who run vending machine businesses no longer have to guess or do the math when it comes to products versus prices and overall profit. The following real benefits are obvious profit boosters.
        Vending machine business owners appreciate all the benefits that DEX technology brings. With all the information about inventory, sales and service readily available at your fingertips or in the office, routes can be planned with greater efficiency, products can be stocked for maximum sales and out-of-order machines can be brought back online quickly. DEX offers exceptional power and utility for the entire vending machine industry and will continue to do so with future advancements and development.
        Because every MDB payment device (Coin validaotr,Bill acceptor, cashless payment module),all has it's own fixed address,and the VMC will only poll these address,so if we want to add a payment device to VMC , we have to do the communication with the VMC through the existing address.
        So we can build a simulator to replace the coin acceptor or bill acceptor,then our simulator will accept the pulse payment input and also built-in the MDB protocal and working with the VMC as a coin validator or bill acceptor. In this case, because our module has already occupied the address of the bill acceptor or coin validator, the original bill acceptor or coin validator can no longer be used.

        We can also adopt another approach. We can use a coin data insertion module to attach to the existing MDB coin validator. If pulse payment is needed, we can temporarily take over the MDB address and communicate payment data with VMC. After the communication is completed, let the original MDB coin validator continue to work. In this case, the original coin validator can continue to be used, but our data insertion module itself cannot work independently and must be attached to the original coin validator.

       Of course, if the vending machine can support cashless payment, we can also use the module as a cashless payment module to minimize the use of traditional payment device addresses.

        Normally customer can order the RS232-MDB box directly from wafer company. For the samples,can order from aliexpress store:

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    Design experts in the field of vending payment products

    WAFER Company is a specialist in vending system design and manufacture the MDB converter for more than 15 years. Since 2003,HUOBEI Powered by waferstar and designed the MDB-RS232 adapter box and registered the brand for kiosk vending machine system application. After around 10 years in the field of MDB payment technology, and become the leading designer and manufacture of payment adapter in China. and also exported to many countries. Can provide self-service payment, comprehensive solutions for products in the field of vending machine systems.

    MDB-RS232®,MDB2PC®,RS232-MDB®,PC2MDB® all are registered brand by waferstar. With rich experience in vending machine cashless payment module and MDB VMC controller design and continuous design updates and upgrades, our products already have a good market sales and long-term operation guarantee, and have won the trust of customers at China and abroad market.

    MDB-RS232®,MDB2PC®,RS232-MDB®,PC2MDB® 均为上海威佛微电子有限公司(waferstar)注册品牌。 凭借在自动售货机无现金支付模块和MDB VMC控制器设计方面的丰富经验和不断的设计更新升级,我们的产品已经具备了良好的市场销售和长期运营保障,赢得了国内外市场客户的信赖。

    MDB-RS232®,MDB2PC®,RS232-MDB®,PC2MDB® son marcas registradas por waferstar. Con amplia experiencia en el módulo de pago sin efectivo de la máquina expendedora y el diseño del controlador MDB VMC y actualizaciones y mejoras continuas del diseño, nuestros productos ya tienen buenas ventas en el mercado y garantía de funcionamiento a largo plazo, y han ganado la confianza de los clientes en China y en el extranjero. mercado.

    MDB-RS232®,MDB2PC®,RS232-MDB®,PC2MDB® sont tous des marques déposées par waferstar. Avec une riche expérience dans le module de paiement sans numéraire des distributeurs automatiques et la conception du contrôleur MDB VMC et les mises à jour et mises à niveau continues de la conception, nos produits ont déjà une bonne vente sur le marché et une garantie de fonctionnement à long terme, et ont gagné la confiance des clients sur le marché chinois et étranger.

    MDB-RS232®, MDB2PC®, RS232-MDB®, PC2MDB® являются зарегистрированными торговыми марками waferstar. Благодаря богатому опыту в разработке модулей безналичных платежей для торговых автоматов и контроллеров MDB VMC, а также постоянных обновлений и модернизаций конструкции, наши продукты уже имеют хорошие продажи на рынке и гарантию долгосрочной работы, а также завоевали доверие клиентов на рынке Китая и за рубежом.

    MDB-RS232®, MDB2PC®, RS232-MDB®, PC2MDB® sind alle eingetragene Marken von Waferstar. Mit reichhaltiger Erfahrung im bargeldlosen Zahlungsmodul für Verkaufsautomaten und dem Design von MDB VMC-Controllern sowie kontinuierlichen Design-Updates und -Upgrades haben unsere Produkte bereits einen guten Marktverkauf und eine langfristige Betriebsgarantie und haben das Vertrauen der Kunden auf dem chinesischen und ausländischen Markt gewonnen.

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