MobilePay POS unit – AT commands

System architecture
The following shows a system diagram of how a POS unit fits into the payment ecosystem
POS system arch

POS unit to Mobile App
The POS unit supports several communication interfaces with a mobile application and is currently based on BLE (Bluetooth Low Energy). A QR code and an embedded NFC tag are also available to provide the POS unit unique identifier and facilitate the commissioning of new POS units in the field.

State definition
The POS unit and smartphone go through a series of states to exchange information. The following describes each of the individual states

  • Check-In Process: To initiate a payment transaction the smartphone must establish a link with the POS unit in order to check-in. In order to check-in, the mobile phone scans for POS units in its vicinity and selects the closest one based on the strongest received signal strength indicator (RSSI).
  • Mobile POS Identifier Process: Once the smartphone and POS unit have established a link, the smartphone will query the unique mPOS identifier (a 15 digit number). This identifier is then validated against the database in Danske Bank, and once it has been validated, the check-in process is completed.

POS unit to POS Interface
The POS unit communicates with a POS by USB and interface with the host through a USB CDC (communication device class) interface. Windows driver is available here.

The POS unit uses an AT command serial interface (Hayes Command set).

PosUnit Connection
- Serial info:

  • Speed: 9600 Baud
  • Data bits: 8
  • Stop Bits: 1
  • Parity: None
  • Row Control: None

All commands are in uppercase and terminate with a carriage return (0x0D) control character. The following diagram shows the communication interface
AT command

AT command

Command Parameters Description Response
AT+BEACONID=? n/a Command to read mPOS 15 digit unique identifier XXXXXXXXXXXXXXX