How to Configure MDB BASIC Templates on VPOS Media 4

Configure MDB transactions for VPOS Media 4 in Nayax Core compare Pre-Selection, Pre-Authorization, and Always Idle BASIC templates with side-by-side setting values and best practices.

General

 

Nayax Core › VPOS Media Configurations

How to Configure MDB BASIC Templates on VPOS Media 4

Set up MDB transaction scenarios for your VPOS Media 4 device in Nayax Core by applying the BASIC template that matches your machine's payment flow: Pre-Selection, Pre-Authorization, or Always Idle.

Operators - Vending, EV & Unattended Retail
Nayax Core - VPOS Media 4
Prerequisites

Before You Start

  • Your machine is a VPOS Media 4. MDB is not available on VPOS Media 4 Mini or other devices in the VPOS Media family.
  • You have Operations > Machines access in Nayax Core.
  • You know which MDB scenario matches your machine's payment flow - Pre-Selection, Pre-Authorization, or Always Idle. See Part 1 to decide.
ℹ️
What is the MDB protocol?
Multi-Drop Bus (MDB) defines how vending machines and payment systems communicate. Each MDB level determines when and how a transaction starts, affecting convenience, speed, and the customer experience. This guide walks you through configuring your VPOS Media 4 device for one of three MDB scenarios in Nayax Core.
💡
What is a BASIC template?
A BASIC template gives you a preconfigured starting point instead of building your configuration from scratch. Entering the template tag auto-populates the essential fields in the Default Configuration tab with the recommended structure for your chosen mode. You then set the value for each parameter and add any additional attributes your machine requires.
Part 1

Choose & Apply a Template

  1.  

    In Nayax Core, go to Operations > Machines and locate your VPOS Media 4 machine.

  2.  

    Open the General tab and decide which MDB scenario matches your machine, then enter its template tag. See the three options below.

    Standard Vending Start with Card - Pre-Selection +
    MDB Level 1 Pre-Selection

    Card first, choose second.

    The customer taps or inserts their card, then selects a product. This is the standard vending flow: the customer pays first, then chooses.

    Template Tag MDB StartWithCard Basic
    ⚠️
    Tag mismatch to confirm: another Nayax U article and a confirmed Nayax Core screenshot both list this template as VPOSM MDB StartWithCard Basic, not MDB StartWithCard Basic. Please confirm the correct tag before publishing.

    Related guide: How to Set Up "Start with Card" MDB Level 1 Pre-Selection | VPOS Media

    Fixed Reserve Start with Card - Pre-Authorization +
    MDB Level 1 Pre-Authorization

    Reserve a fixed amount, then choose.

    The customer taps or inserts their card, and a pre-authorized amount is charged before product selection.

    Template Tag MDB PreAuth Basic
    ⚠️
    Tag mismatch to confirm: another Nayax U article and a confirmed Nayax Core screenshot both list this template as VPOSM MDB PreAuth Basic, not MDB PreAuth Basic. Please confirm the correct tag before publishing.

    Related guide: How to Set Up "Start with Card" MDB Level 1 Pre-Authorization | VPOS Media

    Retail-Style Always Idle +
    MDB Level 3 Always Idle

    Browse first, pay second.

    The device stays idle. The customer selects a product on the machine, then pays - the most retail-like experience of the three scenarios.

    Template Tag MDB Always Idle Basic
    ⚠️
    Tag mismatch to confirm: another Nayax U article and a confirmed Nayax Core screenshot both list this template as VPOSM MDB Always Idle Basic, not MDB Always Idle Basic. Please confirm the correct tag before publishing.

    Related guide: How to Set Up MDB Level 3 Always Idle | VPOS Media

Part 2

Compare Settings & Save

These attributes control the MDB behavior for each mode. Values shown are Nayax recommended defaults.

Nayax Core Field Pre-Selection Pre-Authorization Always Idle
Card Readers
Card Reader MDB Level 1 1 3
Decimal Place 2 2 2
EMV Contactless Transaction Limit 0 0 0
* Transaction Start Method Mag+Contact+
Contactless		 Mag+Contact+
Contactless		 Product
Communication
Communication Mode MQTT Enabled MQTT Enabled MQTT Enabled
Device Features
Data ReductionIf DEX is connected, adjust the DEX settings 16 No DEX on Restart 16 No DEX on Restart 16 No DEX on Restart
MDB
Cashless MDB Address Cashless Device #1 Cashless Device #1 Cashless Device #1
* MDB Flags 02 Pre-selection Enabled Flags Disabled 02 Pre-selection Enabled
* MDB Level 3 Optional Features - - Enable "Always Idle" state
Payment
Default Credit Operator SetsSet higher than the most expensive product Operator SetsSet higher than the most expensive product Operator SetsSet higher than the most expensive product

* = Differs between MDB templates

⚠️
BASIC = minimum required fields. These templates contain only the essential configuration. You must add any additional attributes your machine requires beyond this basic setup. Default Credit must always be set - it pre-authorizes payment to cover purchases and prevents non-payment.
  1.  

    Set the value for each attribute in the Default Configuration tab using the table above, then select the checkbox next to each attribute you changed.

  2.  

    Click Save.

    ✅
    What you should see: your configuration values are saved to the machine record, but not yet pushed to the device.
  3.  

    Click Actions > Update Queue to push the changes to your device.

Recommendations

Best Practices

DO

Set Default Credit higher than the price of the most expensive product on the machine. After entering the amount, select the checkbox to enable it.

DO

After configuring each attribute, select its checkbox on the left. When ready, click Actions > Update Queue to push the changes to your device.

DO

Use MQTT Enabled for communication mode. VPOS Media supports MQTT connectivity.

DO

Match Transaction Start Method to your MDB level: use Mag+Contact+Contactless for Level 1 scenarios and Product for Level 3 Always Idle.

DON'T

Do not use VPN mode. VPOS Media supports MQTT connectivity only.

DON'T

Do not use "Accept All" as the transaction start method.

Outcome

Result

🎉
Your VPOS Media device is configured.

Once your selected BASIC template is applied and pushed via Update Queue, your VPOS Media device runs the MDB scenario you chose - ready to process transactions in the order that matches your machine's customer flow.

Nayax Core › Operations › Machines › [Your Machine] › General › Model Name › Default Configuration › Actions › Update Queue
Help

Troubleshooting

My changes aren't reflected on the device +
Confirm you selected the checkbox next to each attribute you changed, then clicked Actions > Update Queue. Configuration values are not pushed to the device until the queue update is sent.
The device isn't communicating after I applied a template +
Check that Communication Mode is set to MQTT Enabled. VPOS Media only supports MQTT connectivity - VPN mode is not supported and will prevent the device from communicating correctly.
Transactions aren't completing as expected +
Verify Default Credit is set higher than your most expensive product and that the checkbox is selected to enable it. An unset or too-low Default Credit can prevent purchases from completing.
My MDB Flags setting doesn't match the table +
Double-check which scenario you applied. Pre-Selection and Always Idle both use 02 Pre-selection Enabled, while Pre-Authorization uses Flags Disabled since pre-selection isn't needed when payment happens before product choice.
Frequently Asked

FAQ

What's the difference between the three MDB scenarios? +
Start with Card (Pre-Selection) charges after product choice. Pre-Authorization charges before choice. Always Idle lets customers browse and select before paying, using MDB Level 3.
How do I apply the MDB template to my machine? +
Enter the exact template tag in the Model Name field on the General tab. It auto-populates the Default Configuration, and you set each parameter's value.
Why does Pre-Authorization have MDB Flags Disabled? +
No product pre-selection happens at the MDB level in this mode, so the Pre-Selection flag isn't needed. The pre-authorization handles payment instead.
Which MDB scenario should I choose for my machine? +
Pre-Selection suits standard pay-first vending. Pre-Authorization reserves a fixed amount upfront. Always Idle gives the most retail-like browse-then-pay experience.
Can I use these BASIC templates on other VPOS Media devices? +
No. MDB is currently available on the VPOS Media 4 device only - it is not available on VPOS Media 4 Mini or other devices in the VPOS Media family.
Nayax U  |  VPOS Media  |  Simplify Payments. Maximize Loyalty.

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