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Newly Developed PC2MDBAPI Android Library for integration with Android Phablets
(smart phone or tablet).

                                                                                                

 

The PC2MDB™

PC2MDB allows the PC to act as a slave device for existing vending machine controllers (VMC).  It allows the PC to act as a cashless device.  The PC2MDB interfaces any MDB vending device to the PC via the serial port..  Perfect for PC interfaces to existing vending machines to allow the PC to control the vending machine. 

The PC2MDB™ is available in several different packages to meet the needs of developers and vending machine owners. Find out which package best meets your needs here


Overview

The PC2MDB is a slave device for an already existing vending machine with a vending machine controller (VMC).  It allows the PC to act as a cashless device and add credit(s) to the vending machine.  Special versions allow the PC to act as a bill validator or coin acceptor/dispenser.  By default the PC2MDB acts as device type 10 (cashless device)

This describes the Interface Protocol for the PC2MDB Hardware circuit. The PC2MDB™ interfaces any MDB vending device (6-pin molex/5pin MTA) to the PC via the serial port (DB-9) Future support may include Universal Serial Bus. The PC2MDB™ protocol is compatible with standard RS-232 Protocol.

PC2MDB requires:

         An IBM PC compatible, with 486 or better processor.
 
        A serial COM port.
         An MDB compatible vending device 
        
External Power supply (Typically 24VDC)
        
DB-9 (F-M) cable and MDB cable

 

Switch #

 

Function

1

OFF

Operational Mode

ON

Ignore DTR

2

OFF

5 Second Start-up delay 

ON

250 mSec start-up delay

3

OFF

5 mSec Response time

ON

1 mSec Response time

4

OFF

440 uSec Inter-byte delay

ON

900 uSec Inter-byte delay

 

 

 

 

Table 1 – Dip Switch Functions

LED DESIGNATION

INDICATION

D2

+5 VDC

D3

TRANSMIT TO MDB

D4

TRANSMIT TO PC

D5

PULSE OUTPUT

Table 2 - LED Functions

JUMPERS

INDICATION

JMP1

MDB2PC RD

JMP2

PC2MDB RD

JMP3

MDB2PC TX

JMP4

PC2MDB TX

JMP5

Not used

JMP6

PULSE OUTPUT

JMP7

NOT IN WHEN JMP6 IS IN SPECIFICATIONS

Power requirements
24 to 35 Vdc
90 ma Typical
300 ma Maximum
Environmental
Operating Temp 32F to 158F
0C to 70C
Storage Temp -22F to 165F
-30C to 74C
Relative Humidity 5% to 95% Non-condensing
Physical Weight
< 1 lb
Physical Dimensions
Length 3.5 inches Width 2.4 inches Height 1.5 inches
Mounting Template
Click here for template
Connector
 Info
PWR 24-35V Pin 2 +24Vdc Nominal
Pin 4 Ground
MDB
 Pin 1 +24Vdc Nominal
Pin 2 Ground
Pin 3 N/C
Pin 4 MDB Receive Data
Pin 5 MDB Transmit Data
Pin 6 Common

RS-232 Pin 1 N/C
Pin 2 PC Transmit Data
Pin 3 PC Receive Data
Pin 4 DTR
Pin 5 Ground
Pin 6 N/C
Pin 7 N/C

Pin 8 CTS
Pin 9 N/C
LED/Jumper Designations
D2 +5Vdc
D3 MDB Activity
D4 PC Activity
D6 Pulse Output Activity
Switch 1: Mode Select 1
Switch 2: Mode Select 2

Figure-2 Connector Pin Outs

Install the PC2MDB

It is time to install the PC2MDB™ itself and move on to the testing phase.  Installation is relatively simple; there are only three connections that must be made for full functioning of the device.  There are connectors on the edge of the board.  One cable plugs into a 24VDC power supply.  The 6-pin Molex connects to the VMC. The final connector is a DB-9 and connects into the back of the computer.  There should be an open port on the back of the computer labeled “SERIAL2” or “COM2.”

Software

Overview

When the master/VMC has data to send we check the mode bit to differentiate between ADDRESS bytes and DATA bytes.  The upper five bits (MSB) of the Address Byte are used for addressing.  The lower three bits of the Address Byte contain peripheral specific commands.  This will allow up to eight instructions to be embedded in the first byte of block. 

 

The PC2MDB sends information generated by the VMC device directly to the PC via RS-232 serial communication.  It responds to polls issued by the VMC.  PC2MDB will ACK only the polls, and commands issued to correct addresses.  The PC2MDB then forwards the commands to the PC.  Once the data has been processed, the PC sends back another set of instructions to the PC2MDB, which forwards these instructions to the VMC only when desired poll/polls have been received.  The information sent to the PC is send as bytes in hexadecimal.  The first byte sent is the device ID.  For example 30 XX means that a bill validator has sent information.  Whereas 08 XX means that a coin mechanism has sent data.  Consult your manual for commands specific to your MDB device.  We have included command sets for various MDB devices in this document.  Please note that all examples of source code are written in MS Visual Basic 5.0

 

PC2MDB Software Communication (vb.net)

 Setup Comm Port 

Import  
  Imports System.IO.Ports
Declare  
  Dim comPort as new SerialPort()
Open  
 

//configure port

With comPort
.BaudRate = "9600"
.DataBits = "8"
.Parity = Parity.None
.StopBits = StopBits.One
.ReceivedBytesThreshold = 1
.DtrEnable = True
.PortName = portName
.Handshake = Handshake.None
.ReadBufferSize = 1024
.WriteBufferSize = 512
End With

//make sure port is closed before attempting //to open

If (comPort.IsOpen = True) Then
comPort.Close()
End If

//open port

Try
comPort.Open()

Catch ex As Exception
msgbox(Err.Number & ", " & Err.Description)

End Try

   



Receive 

Receive Data  
 

Private Sub comPort_DataReceived(ByVal_ sender As Object, ByVal e As_ SerialDataReceivedEventArgs)

Try

Dim tmp As String = ""

If comPort.BytesToRead > 0 Then
tmp = comPort.ReadExisting()
mdbInput = tmpD
End If

Catch ex As Exception
msgbox(Err.Number & ", " & Err.Description)
End Try

End Sub

   


Transmit

Transmit Data  
 

//transmit hex values in binary
// Begin Session Command with $2USD funds //(0x03 0x00 //0x28)

Try

comPort.Write(ChrW(&H3) & ChrW(&H0) & ChrW(&H64))

Catch ex As Exception
msgbox(Err.Number & ", " & Err.Description)
End Try

 

   



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