MDB-RS232® (MDB2PC®)

For Easy Vending Machine Payment System Design

An easy-to-use, powerful MDB converter. It can connect MDB interface bill acceptor, coin validator, and cashless payment device to RS232 interface Computer, Android motherboard, PLC or Raspberry Pi board. Complete a reliable payment system for the vending machine.

How does the MDB-RS232 work with the PC?
All data from the MDB payment devices (Bill acceptor, Coin validator and Cashless device) are available to the PC. Additionally, all commands can be sent to the MDB device from the PC (ie. Dispense, Enable, Disable etc...) The MDB-RS232 interfaces the MDB vending devices to the PC via the RS232 serial port (DB9).

MDB-RS232® (Pro Engineer)

Support Age Verification and USD device

If you need to develop vending machines for selling similar products such as cigarettes or alcohol products. In some countries, these products may be restricted to different ages, so the vending machine needs to confirm the age of the purchaser before the automatic vending.
Therefore, when you develop a vending machine, you need to have an MDB age verification interface. Or reserve the interface that may be needed for later expansion. Of course, our version of the MDB box is fully compatible with other versions..

MDB-RS232® (Raspberry Pi Hat Version)

MDB2PI - Easy to Design a Smart Raspberry pi VMC

The MDB Raspberry Pi Box (mdb2pi) is your good solution for an MDB integration with Raspberry pi. It can fit a Raspberry Pi, an MDB2Pi board and comes in a one box.This gives you all the features of the MDB-RS232 and the convenience to fit together with the Raspberry pi.
The MDB Raspberry Pi Box makes it easy to develop a smart MDB vending machines. The MDB2Pi inside the box takes care of the MDB specific 9-bit format and timing constraints and simply forwards the MDB data to your application running on the Raspberry Pi, using a simple serial protocol.

About The MDB-RS232 Adapter box

Smart MDB communication module for vending machine design!

Smart Designed MDB-RS232 Adapter Box

The vending industry standard NAMA Multi-Drop Bus (MDB) may now be interfaced to a PC using the MDB-RS232. The MDB-RS232 allows Coin Acceptance, Change Dispensing, credit card reader and bill validation all controlled by the PC.

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

We have been designing the MDB adapter for more than 15 years, and the updated version of MDB-RS232 will always be compatible with the previous version. Therefore, users can use our equipment with confidence, even if our products have been updated and your technical staff may have left. But our new MDB box will remain compatible. You can still buy it directly, plug and play. It will not cause you to be unable to provide services to customers because you cannot purchase the previous adapter.

MDB-RS232's Main Features

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

We Design, Manufacture and Sale

Hot-selling products from WAFERSTAR related to vending machines!

How the MDB-RS232 Works? Play And Watch!


View MDB-RS232        Raspberry Pi version

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Relative products

We have a series of related products available!


COM Version

  • RS232 interface
  • Good Technical Support
  • Long-term application guarantee
  • Simple and Professional
  • Online Skype Service
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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 Cashless Payment

  • Different from MDB-RS232
  • For existing vending machine
  • Working as mdb cashless payment device
  • Simple and Professional
  • Online Skype Service
Order Now

Download the Files

Download the manual and Start to order the samples to test.Believe WAFERSTAR will give you a surprise start!

descargar manual Руководство по быстрому запуску

Frequently Questions and Answers

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

    The first purpose of the MDB-RS232 (MDB2PC) is to build a vending machine. Your motherboard, such as an Android motherboard, Raspberry Pi, an industrial computer, or PLC does not have an MDB interface, and the payment device for example coin validator,bill acceptor you choose is an MDB interface. Then you need this MDB adapter.
    MDB is the protocol developed by NAMA members. The "Multi-Drop Bus" (MDB) protocol is not compatible with the standard PC RS232 protocol and therefore a hardware and software converter is necessary. The MDB-RS232 is a designed to convert the MDB protocol to an RS232 protocol and also performs the necessary voltage conversion. The MDB-RS232 also relieves the Polling requirements thereby allowing the same PC to perform other tasks easily.
    The MDB-RS232 is necessary to interface the standard Vending machine MDB protocol to a standard PC because:
  •  The MDB uses 11 Bits and a nine (9) bit byte.
  •  The polling requirements for the various MDB devices are excessive (20-200 ms) but the normal PC can not meet the polling requirements.
  •  The MDB-RS232 takes care of the polling requirements and generates an interrupt on the serial port of the PC.
  •  This methods allows the PC to perform normal operations and respond to interrupt driven comm events in the UART buffer.
  •  All data from an MDB device is available to the PC.
  •  Additionally, all commands can be sent from PC to the MDB device.
  •  The MDB-RS232 interfaces the MDB vending slave device to the PC via the serial port (DB9).
  •    Firstly, You need to prepare a DC24V power adapter in advance, current can reach at least 3A DC power supply. This is because while the adapter supplies power to the MDB box, it also supplies power to payment devices such as bill validator and coin acceptor through the MDB wire from the adapter box. Therefore, sufficient supply current is required. You need to confirm whether your motherboard has a COM (DB9) port. If not, you may need to prepare a RS232 to USB adapter in advance. Of course, you can directly order MDB-RS232 with USB interface later.
    Of course, the MDB-RS232 of the USB interface is connected to the motherboard, and the USB driver needs to be installed on the motherboard. In this way, when the USB version of MDB-RS232 is plugged into the motherboard, a virtual COM port will be generated. The RS232 communication control can be carried out in accordance with the COM port mode.
       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 VMC 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.
        Therefore, after received the MDB-RS232 samples, you need to connect the MDB bill acceptor and coin acceptor (of course we also can connect the MDB cashless device together at the same time), connect the other DB9 end to the computer, and turn on the Waferstar's MDB pc test tool (open the correct serial port). Then start to power on the devices with DC24V. After power is supplied, MDB-RS232 will automatically send polling POLL commands to each MDB device, and all valid data after the device is powered on will be forwarded to the computer's serial port. At the same time, you can also send MDB commands to control the payment device through the MDB test software. For example, "Enable", "Disable" and so on. You can use bill currency and coins for testing. After receiving the banknotes or coins, the data will be sent to the computer in time.
        In this way, after a simple test, we will have a preliminary understanding of the MDB protocol and commands. Then we can compare the MDB protocol to learn and understand according to the sent commands and the received data.
        Next, you can start your own application design, you can choose to use the WINDOWS system, of course, many customers will also choose to use the Android system motherboard.
        Of course, there will be some problems in the your design process, and we can also consult the technicians of waferstar. We will provide the best assistance to help you understand and complete the project design quickly.
       After purchasing WAFERSTAR's MDB-RS232, 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 control the mdb payment device with WAFERSTAR's demo PC test software. Such as receiving payment, enabling and disabling devices, etc.
       Of course, if you need the source code of the PC test software, you need to purchase the SDK. The SDK also includes more detailed and Quick-response technical support (this is the key point) and two USB-to-serial adapters.
       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.
        On the WAFERSTAR online store,we have MDB-RS232 box and also has a new model 2020 version MDB-RS232, Normal MDB-RS232 will send the enable command to the connected MDB coin acceptor, bill acceptor and the cashless device, but the 2020 Version MDB-RS232 will not do the job, just start to poll the slave payment devices and VMC will need to send these commands. So if we connect the coin and bill acceptors to MDB box and powered on, Even PC is not connected, Normal MDB-RS232 will enable the coin acceptor and bill acceptor and is ready to accept the coin or bills. But V2020 Version box, after powered on, all payment devices are in the disable status.
        Of course, for new users, we strongly recommend the 2020 new version of MDB-RS232. Because the new version not only has some command optimizations, but also supports more slave devices, such as Cashless 60H address device, USD devices, etc., which can facilitate subsequent system upgrades. As for the old users, if they don't want to change the software, or for the convenience of after-sales, they can continue to use the previous version of MDB-RS232.

        In WAFERSTAR's online shop, there is an MDB-RS232 adapter. There is also an RS232-MDB adapter. They look similar in appearance, but they are actually two completely different products. If customers do not read the product description carefully,then will easily place an order incorrectly. 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 the RS232 device, for example a computer or PLC. 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,POS or other RS232 devices and work as the slave cashless payment device.and then you PC will work as a cashless payment device to existing 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 MDB-RS232. Order Samples now! .........
  • Now I understand the difference between them, what I need is RS232-MDB. I want to continue to learn about RS232-MDB..........
  • 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.
        In fact, because any MDB cashless payment device needs to comply with the standard protocol, it can be connected to the Android motherboard via MDB-RS232 and send commands to control it.
        Of course, Cashless payment equipment is different from cash payment (bill or coins), and generally requires the support of the card issuing company.
        For example, credit card payment needs to be approved by the bank at the time of payment. Therefore, Cashless devices need to be connected to the payment system before they can be used.
        Such as NAYAX equipment, although it can be connected to any vending machine. However, you must be sure it can be connected to the NAYAX system through other 4G or other networks. The Nayax system need to confirm the security and registration of the device. Therefore, when using this type of device, you must first communicate with the service provider for example Nayax company to ensure that the device you need to use is valid and can connect to the payment system.
        In fact, there is Fast User Manual for use, plus a preliminary test with the PC test tool. Software Engineer will have a basic understanding of MDB payment equipment and protocols. We do not recommend customers to purchase SDK. After purchasing samples and testing the equipment in accordance with the manual, the remaining work is actually the software design of the vending machine system for the customer. The MDB payment part is only a very small part of the software system (of course the stability of the payment system is very important). Therefore, an experienced software engineer can easily complete the design of the serial communication part.
        Of course, if Engineer is not an experienced serial port communication design, or want to simply understand the command design and processing, you can also buy the SDK. The SDK mainly includes the source code of the PC test tool. The most important thing is that if you purchase the SDK, we will provide more technical support for the MDB protocol. Such as protocol analysis, instruction processing, and flow design. These can save you part of the design time.
        Of course, our services will not be specific to a certain programming language, nor will we analyze the customer’s software code.
        MDB-RS232 is just a payment device used to connect the MDB interface, such as bill acceptor, coin validator, and Card readers (Cashless device) to serial devices, such as your Android main board, your industrial computer (PLC), etc., to complete the payment interface. In this way, you can design a program on the VMC to control the payment device and receive payment data.
        In other words, MDB-RS232 is only an interface for receiving and paying, not all of the vending machines. You also need to configure the power supply system, drive circuit, sensor circuit and so on.
        For example, if you need to design an information query machine, you may need a printer to be connected.
        For example, if you are designing a self-service coffee machine, you may need a drive board, the main board sends instructions to drive the motor to grind coffee, and needs to detect the status of various sensors and so on.
        In fact, this is not necessarily true.
        Because there are many kinds of payment devices, such as pulse interface (of course you will need a pulse-to-serial device, we can also provide it). You can also directly use payment devices with RS232 interface. Then you can directly connect to the serial port of VMC. Of course, the biggest problem of this design is that the serial port protocol is not an international standard protocol, it is a protocol defined by each manufacturer. This is not universal and replaceable. That is to say, you must use the same equipment when you maintain and upgrade in the future. If you export to other countries, the maintenance of the sales will be very troublesome.
        The MDB interface equipment is an international standard. Any brand manufacturer, any currency type equipment, any coin device, banknote device, credit card reader, as long as it is an MDB interface, must comply with the same protocol. In this way, it can be easily replaced with any manufacturer's equipment during post-production and maintenance, and will not be restricted.
        1. We are a company established in 2006 with a history of 15 years. We have been engaged in the production of MDB adapters for more than 12 years. If it is our old customer, you will know our design history. Years of design experience and product updates have given us rich experience in production, design, maintenance and technical support.
        2. Since the system design, sales and market training of vending machines take a long time, we can continue to provide technical support and after-sales service for many years. If you choose a product from an unstable company, after you complete the design, the supplier company may go bankrupt, business changes, product discontinuation, product quality issues and other accidents may occur, resulting in the embarrassment that you cannot continue to buy. Or after encountering some product or technical problems, you will never get technical support or solutions.
        3. We have a competitive price. Of course, for self-service vending products, price is definitely not the most important thing, because stability is very important in unattended situations. Only then can the machine generate trouble-free benefits for customers.
        4. We provide solutions and upgrades for a series of products, and our upgrades will provide compatibility. To provide our customers with good product support.
        1. Our 2020 verion MDB-RS232 box and the MDB-RS232 Pro engineer version can support the cashless 01 and cashless 02 at the same time.
        2. Our MDB Pro Engineer version also can support the USD and Age verification
        3. Normally for new customer,just use our MDB-RS232 V2020. if you need to develop the vending machine with the age verification function,then would need to order the Pro engineer version.
        Yes,we will provide the necessary technical support for USD and AGE Verfication device test. of course,you need firstly order or have a standard MDB interface USD (slave) or AGE Verfication device. or you can order a simulator box for Age or USD device.
        1. Select a Android main board to work as the vending machine master board.
        2. Order a MDB-RS232 Professional version adapter box.
        3. Order a MDB Interface Age verification slave device,if you don't have a real age verification device, just want to verification the function,you can order a Age verification simulator box from the waferstar company. Of course, it is best to order a standard MDB interface AGE verification device.

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

    Go to order the samples

    Order the samples from Online WAFERSTAR Aliexpress store.


    Design experts in the field of vending machine 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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