Introduction: A Promising Opportunity
When one of our long-time clients approached us with a new challenge, we were immediately excited. They wanted to extend their payment management solution to include credit and debit card processing—directly through a dedicated Android-based payment terminal.
At Zarego, we have deep experience in developing custom software for mobile platforms, so working with Android was familiar territory. What made this project unique, however, was the specific device: a PAX A920 terminal. These devices are widely used in the retail and finance sectors, but they come with their own set of complexities—tight security controls, limited hardware, and a fragmented developer ecosystem.
This project pushed our team to think creatively, work collaboratively, and dig deep into our technical expertise.
The Challenge: Custom Android Software for Secure Devices
While building Android applications is second nature to us, deploying one on a device like the PAX A920 presents a number of unique hurdles.
First, the device operates under strict security protocols because it handles highly sensitive financial data. It has limited system resources and uses a version of Android that’s often customized and outdated. This means that even basic development tasks can become difficult.
On top of that, the available documentation was often incomplete, scattered, or outdated. Much of it had to be sourced manually, sometimes through trial-and-error, and sometimes through direct communication with the vendor. Simply gathering the technical information needed to get started was a project in itself.
This wasn’t your typical mobile app. It was a full integration with the real-world ecosystem of credit card payments—and every detail mattered.
Understanding the Two Approaches: Semi vs. Full Integration
When building software that processes card payments for PAX, there are two principal integration strategies:
- Semi-Integration
This approach relies on SDKs provided by the device vendor—like BroadPOS or Portico—to handle sensitive aspects of the payment process. The SDK manages things like card data, encryption, and secure communication with banking systems. It’s a safer and more streamlined option for developers who want to delegate responsibility for PCI compliance and data security. - Full Integration
In a full integration, the development team takes full control of the payment flow. This includes managing sensitive data, handling certifications, and building everything from the ground up. While it offers more flexibility, it’s a high-stakes path that requires deep technical expertise and rigorous security standards.
For this project, we had to carefully weigh both approaches and determine which one best met the business goals, technical needs, and timeline. Ultimately, we opted for a semi-integration, balancing control with security and leveraging the SDK where it made sense.
A Seasoned Team Tackling Real-World Problems
What made the difference in this project wasn’t just our technical knowledge—it was the breadth of our team.
From project managers and QA analysts to senior Android engineers and DevOps specialists, we brought together a multidisciplinary team with the experience to navigate unexpected issues quickly and efficiently.
Where a solo developer or freelance contractor might have been overwhelmed by the complexities of integrating with PAX, our team thrived. We assigned specific tasks, created small isolated tests, and shared insights continuously. The result was a problem-solving culture that transformed blockers into learning opportunities.
Every challenge we encountered—from missing SDK features to unclear documentation—was met with collaboration, creativity, and persistence.
The Technical Process: From Experimentation to Deployment
Our work began with an in-depth investigation of the PAX SDK and supporting documentation. Since the documentation wasn’t centralized or well-maintained, we had to actively engage with the vendor and test our own assumptions through experimentation.
We broke the system down into manageable components:
- SDK research and validation
- Designing a simple, intuitive UI for store staff
- Architecting the backend and API integration
- Developing and testing the Android app
- Ensuring smooth communication with the client’s existing system
Each component was built and tested in isolation, then gradually integrated into a complete solution. This modular strategy allowed us to move fast without sacrificing stability.
One of the keys to our success was our internal QA process. We simulated real-world payment scenarios—swipe, chip insert, NFC tap, and even manual card entry—ensuring that the app performed reliably under all conditions.
The Final Solution: Secure, Flexible, and User-Friendly
The final application was deployed directly on the PAX A920 and is now in active use across multiple retail locations.
It supports a full range of payment methods, including:
- NFC contactless payments
- Chip and PIN (EMV)
- Magnetic stripe swipe
- Manual card data entry (when necessary)
More importantly, the application integrates seamlessly with the client’s backend systems, allowing real-time transaction syncing, status monitoring, and payment confirmations.
The app was built with extensibility in mind. Thanks to its modular architecture, the client can easily scale the product, roll out new features, or adapt it to new devices or regions without having to rebuild from scratch.
The Results: A Win-Win for Our Client and Their Users
The solution we delivered met and exceeded expectations.
Here are just a few key results from the project:
- Faster time-to-market thanks to our semi-integration strategy
- Reduced training time due to the app’s clean, intuitive interface
- Improved operational efficiency for retail staff
- Secure transactions that comply with industry standards
- Scalable architecture ready for future growth
By choosing a nearshore partner like Zarego, the client gained access to a high-caliber technical team at competitive rates—without sacrificing quality or communication.
Why Work With Zarego?
If your business needs to build a secure, integrated application for specialized hardware, you need more than just a developer—you need a team.
At Zarego, we bring together:
- Senior developers with proven mobile and backend experience
- Project managers who keep things on track and on budget
- QA testers who ensure your solution is robust under pressure
- DevOps experts who handle deployment, updates, and scalability
- A collaborative culture that treats your goals as our own
Whether you’re working with card payment terminals, smart devices, or complex backend systems, we’re ready to bring your vision to life.
Conclusion: From Challenge to Competitive Advantage
We began with a technical challenge due to fragmented documentation on PAX terminal integrations. Thanks to the collaborative efforts of our team at Zarego, the payment management solution is now smarter, faster, and more reliable.
This case illustrates what’s possible when the right mix of people, process, and technology come together. From exploring SDK documentation to deploying a production-ready Android application on a secure payment device, every step of the journey was handled with care, creativity, and expertise.
Do you have a similar challenge?
Let’s talk. We’d love to help you build your next great solution.
