User Interface Requirements

Integrating the UNO-mini requires your enclosure and display to meet specific EMVCo certification requirements for logos, LEDs, and audio feedback.

EMV contactless logo

The EMV contactless logo must appear on your machine panel at the same position as the logo printed on the UNO-mini device: the center of the antenna. When reproducing the logo, follow the EMVCo sizing, clear space, and color rules. See the EMVCo Contactless Symbol Reproduction Requirements for the full specification.

Card scheme brand guidelines

Card scheme logos on the machine panel or display are optional. If you choose to display them, they must comply with each scheme’s brand guidelines. The following table lists the brand guidelines documentation for each major card scheme.

Card scheme	Brand guidelines
Visa	Visa Merchant Signage
Mastercard	Mastercard Brand Center
American Express	American Express Checkout
Discover	Discover Global Network Signage and Logos

LED and audio requirements

The UNO-mini has 4 green LEDs on its front panel. These LEDs are required by EMVCo for POS devices and must be visible to the end user.

There are two compliant ways to present the LEDs to the end user:

Create a transparent area in the machine panel to expose the original device LEDs directly.
Simulate the LED states on the machine display screen, if one is present.

LED and audio states

The following table lists all LED and audio states as defined in EMVCo Book A v2.10, sections 9.x. LED legend: ○ Off, ● On. Blinking states are noted in the LED pattern column. Audio tones:

Success tone: approximately 1500 Hz sine wave, 500 ms
Alert tone: approximately 750 Hz double beep (200 ms on / 200 ms off / 200 ms on)

Status	Msg index	Description	LED pattern	Message display	Audio
Not Ready	—	Reader not powered or not communicating	○ ○ ○ ○	No message	None
Idle	17	Powered and connected, not polling for card. First LED blinks approximately 200 ms every 5 s.	● ○ ○ ○ (blink)	Welcome	None
Ready to Read	1	Polling for card. Transaction amount may be shown.	● ○ ○ ○	€ xx.xx / Present card	None
Card Read Successfully	35	All four LEDs light in sequence over approximately 250 ms, then remain lit for approximately 750 ms, then turn off. Total duration: 1000 ms.	Sequential flash (all 4)	Card read OK / Remove card	Success tone
Authorizing	36	Online authorization in progress	○ ○ ○ ○	Authorizing / Please wait	—
Approved	6	Transaction approved by issuer or by terminal offline decision	○ ○ ○ ○	Approved	None (success tone played at card read)
Not Approved	9	Transaction declined by issuer	○ ○ ○ ○	Not Approved	Optional alert tone
Declined	255	General decline	○ ○ ○ ○	Declined	Optional alert tone
Read Error	39	Error occurred reading the card	○ ○ ○ ○	Read error / Please try again	Optional alert tone
Conditions Not Satisfied	38	Contactless conditions not met, for example when risk management requires a contact chip	○ ○ ○ ○	Please try another card	Optional alert tone
Contactless Collision	5	Multiple contactless cards detected simultaneously	○ ○ ○ ○	Present one card only	Optional alert tone
Timeout / No Card	30	Transaction timed out with no card presented	○ ○ ○ ○	Timeout / No Card	Optional alert tone
Terminated	10	Transaction terminated by terminal or application	○ ○ ○ ○	Terminated	Optional alert tone
PIN Entry Required	11	Card requires PIN entry, which cannot be performed via contactless	○ ○ ○ ○	Please try another card	Optional alert tone
See Phone	12	Mobile device requires customer action, such as unlocking or approving on the phone	○ ○ ○ ○	See Phone	Optional alert tone

Next steps

Power Supply

Review power requirements and wiring recommendations before connecting the device.

Connection Interfaces

Connect the UNO-mini to your host controller via USB or UART TTL.

EMV Core Guides

Android & Linux SDK

RTOS SDK

UNO-mini Hardware

Release Notes

EMV contactless logo

Card scheme brand guidelines

LED and audio requirements

LED and audio states

Next steps

Power Supply

Connection Interfaces

​EMV contactless logo

​Card scheme brand guidelines

​LED and audio requirements

​LED and audio states

​Next steps

Power Supply

Connection Interfaces

EMV contactless logo

Card scheme brand guidelines

LED and audio requirements

LED and audio states

Next steps