Poplapay Android SDK provides Bluetooth connectivity for payment terminals such as SPm20. It is being provided as open source for direct integration in to Android applications.
The SDK manages the Bluetooth connection to the payment terminal and performs the network proxying and rate limiting to provide the terminal a stable connection to the internet. Additionally the SDK provides a JSON-RPC connection class for application use to directly talk to the terminal utilizing the JSONPOS API.
GitHub repository: https://github.com/poplatek/pt-android-sdk
If cloud connectivity using WebSocket is utilized to connect to the terminal, a separate Poplapay Connector application can be used instead. It can be used to pair and maintain a persistent Bluetooth connection to the terminal while the Connector application runs in the background.
By utilizing cloud connectivity and Poplapay Connector payment terminals may be integrated to any cash register application without requiring any SDK to be integrated in to the application.
See also Spire SPm20 developer notes.