Dual-Sided Portable POS Android App

**Android App Development for Dual-Sided Portable POS Terminal (Payconiq + Cash Machine + Compact POS)** We need an experienced Android developer to build a custom native Android application for a dual-sided portable POS device (similar to the ZCS Z108: Android 14, 8-inch main touchscreen 800x1280 + 2.6-inch secondary customer-facing screen, octa-core, 4GB RAM/32GB ROM, Bluetooth, WiFi, optional 4G, rear camera/barcode scanner support, 58mm thermal printer, NFC optional). ### Core Requirements 1. **Payconiq QR/Barcode Generation (Priority)** Integrate with the official Payconiq Merchant API (v3) so the merchant can enter an amount on the main screen and instantly display a scannable Payconiq QR code on the secondary customer-facing screen (and/or main screen). - No need for the merchant to use a personal smartphone. - Support dynamic QR codes (amount + optional reference/description). - Handle payment status (pending/success/failed/expired) via API polling or webhooks/callbacks. - Display clear confirmation on both screens. - Proper error handling, API key/merchant ID management, and compliance with Payconiq branding guidelines for the QR code. 2. **Cash Machine / Cash Device Integration** We already have working source code from an existing Android tablet app that communicates with our cash device via **Bluetooth **. - Port / adapt this communication layer into the new app. - Support cash payment flow in real time > client can choose to pay cash or payconiq - Reliable connection management, reconnection, and status feedback. 3. **Barcode Scanning** Use the device’s built-in rear camera to scan product barcodes (or customer barcodes). - Fast, reliable scanning with visual/audio feedback. - Add scanned items to the cart. 4. **Compact POS System** Build a simple, fast, and clean point-of-sale interface optimized for the dual-screen form factor and portable use: - Product catalog / quick-sale buttons (categories + searchable items). - Cart management (add/remove/quantity/discount). - Multiple payment methods: Payconiq (primary), Cash (triggers cash machine), and placeholder for future methods. - Receipt printing via the built-in 58mm thermal printer. - Basic sales history / daily summary. > pushed to a cloud as backup - Simple settings (merchant credentials, printer, cash drawer, language). - Optimized UI for both merchant (main 8") and customer (2.6" secondary) screens. - Offline-tolerant where possible (queue payments when needed). ### Technical Expectations - Native Android (Kotlin preferred, Dart ,Java acceptable). - Clean, maintainable architecture (MVVM or similar). - Proper handling of dual displays. - Secure storage of API keys and credentials. - Support for the target hardware (Z108-class devices running Android 14). - Source code delivery + basic documentation + handover. ### Deliverables - Fully working APK + full source code on GitHub - Integration of the existing cash-device communication code.(code available) - Working Payconiq QR generation and status handling. - Barcode scanning and basic POS flow. - Short user/admin guide. ### Preferred Skills - Strong Android native development experience. - Previous work with POS / dual-screen devices / payment terminals is a big plus. - Experience with payment APIs (especially QR-based such as Payconiq, or similar). - Bluetooth + TCP/IP socket communication. - Camera / barcode scanning libraries (ML Kit, ZXing, or hardware scanner SDKs). Please include in your proposal: - Relevant experience (POS, dual-screen, payment integrations). - Estimated timeline and fixed price or milestone-based quote. - Any questions about the existing cash-device source code or Payconiq account access. We will provide the existing cash-device source code, device access/details, and Payconiq merchant credentials after NDA/signing. Looking for a reliable developer who can deliver a solid, production-ready solution.