Card Terminal Payment App Integration

I need a developer who can wire an in-person card terminal to a brand-new standalone payment application I’m building. The goal is simple: when a customer taps, dips, or swipes on the physical device, the transaction data should flow instantly into my app, be authorised, and return a clear success or decline message that I can display in the UI.

Scope
• Pair the terminal with the app over USB, Bluetooth, or LAN—whatever the chosen hardware supports best.
• Build the payment flow: initialise transaction, capture amount, collect signature/PIN where required, post-authorise, and close.
• Expose the result to my frontend through a clean REST or WebSocket interface so I can update order status, print/email receipts, and trigger inventory calls.
• Provide a small test harness so I can run dummy and live transactions before launch.

Provider flexibility
I haven’t locked in the hardware yet, so the code should be modular enough to drop in Stripe Terminal, Square, or even a bank-issued device without major rewrites. If you have a strong recommendation, include that in your proposal and tell me why—API maturity, fees, or ease of certification.

Deliverables
1. Source code (app side + terminal SDK integration)
2. Clear setup instructions and environment variables
3. Written walkthrough of the transaction lifecycle and any PCI considerations
4. A demo video showing a live tap or chip payment flowing end-to-end

Acceptance Criteria
• Card tap/dip/swipe processed with real or test card and reflected in the app within 3 seconds.
• Full reversal/refund supported.
• No plaintext card data exposed anywhere in logs or memory dumps.

If you’ve handled hardware payment integrations before and can move quickly, let’s talk timelines and milestones.