MDB Cheat Sheet
This page provides some useful information about the MDB Standard to help you understand a little how the protocol works, and have some more information to hit the ground running on the MDB Project.
Always Idle vs Authorization First
Always Idle(AKA Selection First) and Authorization (AKA Auth First) are two terms that you will see floating around our documentation space and our MDB Lingo.
These refer to the user flow of Cashless Payment devices in regard with the timing of selection and Card Swiping. Please find the different flows on the table below.
| Always Idle Flow | Auth First Flow |
|---|---|
| 1 - User selects the product on the vending machine 2 - Product price is requested at the Payment Terminal 3 - User swipes the card to allow payment. 4 - The machine dispenses the product and confirms transaction to the terminal without any action necessary from user. | 1 - Terminal is requesting for a pre-defined authorization amount. 2 - User swipes the card to pre-authorize (reserve) the authorization amount. 3 - User selects the product on the vending machine. 4 - The vending machine sends the item price to the terminal. 5 - The terminal adjust the value to charge to the customer and confirms it to the vending machine without any necessary action from user. ** 6 - The vending machine dispenses the product and confirms transaction **without any necessary action from user. |
Cashless Payment on MDB
Not all Vending Machines are capable of accepting Cashless Payments. Earlier versions of the MDB Specification allowed only Coins and Bills. If the machine is not compliant with such versions, it is not possible to use Cashless Peripherals as Payment Media on them.
MDB Pinout
There are 2 MDB Connectors, one typically used in the Vending Machine Controller (VMC) boards, and other typically used in Peripherals such as Coin Acceptors, Cashless Payment Terminals, Bill Acceptors or Telemetry devices.
These connectors' pinout is shown in the diagram below, with a real connector example for each connector type.
Each pin function is explained in the table below the pictures.
| Pin Number | Description |
|---|---|
| 1 | Minimum - 20VDC | Nominal - 34 VDC (MDB Power High) |
| 2 | DC Power Return (MDB Power Low) |
| 3 | Not Connected |
| 4 | Master Receive |
| 5 | Master Transmit |
| 6 | Communcations Common (Comms line GND) |
Approved Suppliers & Part Numbers
Suppliers
| Molex | Mini-Fit, Jr.TM Product |
|---|---|
| AMP | AMP-DUACTM Product |
Peripherals
| Connector | Six (6) Circuit Receptacle Housing |
|---|---|
| Molex | 39-01-2060 |
| AMP | 106527-6 |
| Terminals | Female Contacts (sockets), Tin |
| Molex | 39-00-0065 |
| AMP | 106528-2 or 106529-2 |
| Strain Relief | The strain relief shall not exceed a Maximum Form Factor of 0.85 inch wide x 0.75 inch high x 1.90 inch long, excluding integrated hinges and wire ties |
| Molex | 15-04-0296 |
| AMP | 1375618-1 |
Bus Harness
| Connector | Six (6) Circuit Plug Housing |
|---|---|
| Molex | 39-01-2061 |
| AMP | 794550-6 or 794542-6 |
| Terminals | Male Contacts (pins), Tin |
| Molex | 39-00-0067 |
| AMP | 794578-1 or 794576-1 |
VMC Connector (Direct PCB Mount)
| Vertical Header | Male Contacts (pins), Tin |
|---|---|
| Molex | 39-28-1063 |
| AMP | 794664-6 |
| Right Angle Header | Male Contacts (pins), Tin |
| Molex | 39-30-1060 |
| AMP | 794448-1 |