Transport & Logistics

The Challenge

Cash processes in the field and at the barrier

Parking operators need dependable mobile checkout wherever staff work: tickets must be validated quickly, without juggling multiple devices, while new sales stay traceable—from customer receipt to finance booking. The solution has to cover validation, issuance, and payment in one coherent flow.

Peripherals, backend, and payment

Mobile printers are often connected via Bluetooth (BLE), while settlement and status updates use Wi‑Fi or cellular paths to backends and card terminals. The architecture must cope with variable connectivity, security expectations around card data, and clear end-of-day reporting—without overloading on-site staff.

Avoiding downtime

Online-only operation is risky in the field: short server or internet outages should not halt sales entirely. At the same time, offline operation must not silently create duplicate bookings or inconsistent ticket states. Balancing availability and data integrity was a core requirement.

Our Solution

Android POS screenshots

Android POS: tickets, payment, printing

We delivered an Android-based mobile POS that reads and validates existing tickets and issues new ones. A BLE-connected mobile printer produces receipts on site. Payment can be cash or card via the integrated terminal, aligned with the customer’s hardware setup.

Cash journal, closing, backend

Collected amounts are recorded in a cash journal and transmitted to the designated backend at end of day—supporting operational control and downstream reporting. Interfaces were shaped to fit existing operating models and to allow maintenance and extensions (e.g. additional payment methods).

Online first, offline when needed

Continuous server connectivity is the default so statuses and settlements stay current. We also implemented an offline mode: during outages, operation can continue under defined rules; when connectivity returns, data is synchronised with conflict patterns kept manageable. The POS stays usable without sacrificing traceability.

Results

Efficiency for teams and processes

Staff work from one mobile device for validation, sale, and receipt—fewer hand-offs between paper, separate terminals, and back-office spreadsheets. Receipts and journal entries stay tied to the transaction; end-of-day closing reduces manual follow-up.

Technical reference for field and IoT-adjacent apps

The project demonstrates how we build Android apps with BLE peripherals, payment integration, and backend sync—from resilient offline behaviour to clear APIs. Delivery by Groenewold IT Solutions in East Frisia; Made in Germany means short communication paths and careful support from concept to rollout.

Quality, security, and maintenance

Operation under time pressure

Flows prioritise short interactions: common steps stay reachable without deep nesting. That lowers training effort and error rates when many staff rotate or change sites.

Secure payment and print integration

Payment and print paths follow device and industry expectations, with traceable logging. Where sensitive data matters, established terminal and backend mechanisms remain authoritative—the app orchestrates without duplicating security-critical logic unnecessarily.

Features

Feature overview

Validation of already redeemed tickets
Issuing new parking tickets in mobile use
BLE connection to a mobile printer including receipt printout
Recording takings in a cash journal
End-of-day closing and transmission to the backend
Cash or card payment (depending on configuration)
Preferred online operation with additional offline mode during outages
Communication with peripherals and backend via BLE, Wi‑Fi, and APIs
Delivered as a client project (internal distribution, no public app store listing)

Mobile POS for Parking Lots – Android, BLE, and Offline Resilience