Link and Events Configuration

This page will explore the essential components and configurations needed to establish and manage the connection between your application and Nayax’s payment devices using the Marshall SDK. This includes:

• Handling events through the vmc_link_events_t interface.
• Understanding the structure of vpos_config_t class.

Refer to the following sections for more information.

Link Events Interface

The vmc_link_events_t Interface defines the events related to the communication link between the vending machine controller (VMC) and Nayax devices. Implementing this interface enables your application to respond to critical events that occur during the device’s operation.

The following code block presents how to add the interface:

Java

public interface vmc_link_events_t
void onReady(vmc_link.vpos_config_t config);
void onCommError();

Interface Methods

The table below describes the available methods of the interface.

Method	Description
onReady()	This method is called when the link with the VPOS (Vend Point of Sale) is successfully established and the device is ready for vending operations. It provides the VPOS’s configuration details.
onCommError()	This method is invoked when a communication error occurs between the VMC and the VPOS, allowing your application to handle such errors appropriately.

VPOS Configuration Class

The vpos_config_t class encapsulates the configuration settings for the VPOS, which are communicated between the VMC and the device. The following code block lists all available configurations:

Java

public static class vpos_config_t 
      public byte   prot_ver_major;
      public byte   prot_ver_minor;
      public byte   language;
      public byte[] country_code;
      public byte[] currency_code;
      public byte   decimal_place;
      public byte[] vpos_serial;
      public int    machine_type;
      public byte[] merchant_id;
      public byte[] acquirer_terminal_id;
      public byte[] machine_location;

Class Parameters

The table below provides a detailed description of the parameters.

Parameter	Type (inferred)	Description
prot_ver_major	int	The major version of the Marshall protocol.
prot_ver_minor	int	The minor version of the Marshall protocol.
language	String	The language setting of the VPOS.
country_code	String	The country code in ISO format.
currency_code	String	The currency code in ISO format.
decimal_place	int	The price is represented as 10 exponents. For example, if the decimal place is 2 and the requested price is 100, then the actual cost is 1.00 (with 2 decimal places).
vpos_serial	String	The serial number of the VPOS.
machine_type	String	The type of machine connected to the VPOS.
merchant_id	String	The merchant ID.
acquirer_terminal_id	String	The acquirer terminal ID.
machine_location	String	The location of the machine.

Callback function

To register the callback events for link operations, use the following method:

Java

public vmc_link set_events(vmc_link_events_t events);

By understanding and implementing these configurations and methods, you can effectively manage the communication link and event handling for Nayax payment devices, ensuring reliable and efficient vending operations.

Communication Loss

The Marshall protocol answers every command with an ACK. When your peripheral sends a command to the device it gets an ACK back, and the same happens in the other direction. The ACK is the receiver telling the sender that the command arrived.

When no ACK comes back, the command is transmitted twice more. If none of the three attempts is acknowledged, the SDK stops sending keep-alive commands and the device sends a reset command to start the pairing process again.

What happens to a transaction that was in progress when the ACKs stopped depends on the stage it had reached. See Create Payments.