Enabling EMV Contactless Payments on Android POS for EU Market

2025-05-25

🏢 Background

A European payment solutions provider (under NDA) approached me to develop a NEXO-compliant, EMV-certified Point of Sale (POS) application from the ground up. The client specializes in Android-based payment terminals and needed a fast, reliable, and fully certifiable POS app for the European market that adhered to NEXO Fast specifications and passed CFCF.eu certification.

Their goal was to deploy the solution across thousands of Newland and Sunmi Android terminals used by merchants in retail and hospitality environments.

❗ The Challenge

Building a POS app for the European market that adheres to NEXO 4 and 5 protocols is no small feat. The system had to:

Support contactless EMV transactions, including secure kernel communication.
Comply with NEXO Fast Application Layer Protocol, which demands rigid adherence to ISO 20022 messaging.
Pass certification through CFCF.eu, requiring strict protocol and functional conformity.
Be efficient and modular enough to run on low-power Android POS terminals.
Be delivered by a single developer within tight deadlines.

Most providers solve this with a large team — but the client wanted an efficient, expert-led solution without compromising quality or certification requirements.

👨‍💻 My Role

As the sole engineer and architect from my OPC company, I led the entire lifecycle:

System Architecture: Designed a modular and testable Android POS framework.
Protocol Implementation: Implemented the full NEXO Fast stack and EMV Level 2 kernel interface.
Secure Integration: Handled transaction flows, card communication, and response parsing.
Debugging & Certification Prep: Simulated test cases, resolved certification issues, and worked closely with the lab for CFCF approval.
Deployment Support: Optimized the APK for Sunmi and Newland hardware and delivered production-ready builds.

💡 The Solution

I developed a fully compliant Android POS app using Kotlin that:

Seamlessly integrates with EMV Level 2 kernels for contact and contactless transactions.
Implements NEXO Fast v4/v5 protocol stack, handling messaging, status words, and session control.
Offers a dynamic merchant interface for transaction display and receipt printing.
Supports fallback and retry mechanisms for real-world payment conditions.
Includes secure configuration loading and transaction logging as per NEXO mandates.

This solution was tailored for Sunmi and Newland terminals, ensuring compatibility with their printer modules, NFC readers, and secure elements.

✅ The Outcome

Successfully certified under CFCF.eu, passing all protocol, functional, and security test cases.
Deployed across 10,000+ terminals in production within the EU.
Reduced client’s go-to-market time by over 6 months compared to outsourcing to a large team.
Delivered an app that is modular, future-proof, and easily maintainable.

🔧 Tech Stack

Language: Kotlin, Java
Platform: Android (Sunmi, Newland)
Protocols: EMV Level 2 Kernel, NEXO Fast v4/v5, ISO 20022
Tools: Android Studio, CFCF Certification Suite, Terminal Simulators
Other: SQLite, Secure Print Modules, Logcat Analysis Tools

🎯 Why It Matters

This case demonstrates that a single-expert company can deliver highly regulated, complex fintech software with agility, quality, and certification readiness. By deeply understanding both the protocols and the business landscape, I was able to offer a faster and more cost-effective solution than larger development houses.