Vladan S.

Senior Android engineer with 10+ years of commercial Kotlin and Java experience, 5,300+ hours on Upwork, and a 4.8 rating. I specialize in the hard part of Android: connecting apps to hardware, payments, and third-party SDKs. WHAT I BUILD - Payment terminal apps: secure NFC card authentication, 3DES/AES encryption, HMAC-SHA256 integrity - Bluetooth and USB integrations: receipt printers, weighing scales, vehicle middleware devices - Android TV apps with ExoPlayer video streaming - Modern UI with Jetpack Compose, Coroutines, MVVM - Legacy rescue: Java to Kotlin, ButterKnife to view binding, AndroidX migration, crash monitoring (Crashlytics, Sentry), unit and Espresso tests RECENT WORK - Payment terminal app (NFC, encryption, printers), current full-time role - Real-time USB industrial scale integration and stability fix - Android TV streaming apps for several agencies - Hours-of-Service app for truck drivers with Bluetooth vehicle middleware Before software I ran an industrial automation consultancy (PLC systems), so I understand how hardware and software really fit together. HOW I WORK Clear weekly updates, clean maintainable code, and fast replies (usually within a few hours, CET). Have a stalled app, a hardware integration nobody wants to touch, or a legacy codebase to modernize? Send me the details and I'll tell you honestly how I'd approach it.