> ## Documentation Index
> Fetch the complete documentation index at: https://devzone.nayax.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Overview

The EMV Core RTOS SDK is a portable C99 library for adding EMV payment to MCU and RTOS-based hardware. Your application calls the SDK APIs; the SDK handles card reading, authorization, and server communication.

<Note>
  This documentation covers SDK v1.0 for MCU and RTOS platforms. For the Android or Linux SDK, see [Android Installation](/docs/integrate-pos-device/emv-core/get-started/emv-core-android-installation) or [Linux Installation](/docs/integrate-pos-device/emv-core/get-started/emv-core-linux-installation).
</Note>

## SDK Highlights

* **C99 source code** designed for embedded systems
* **Complete EMV transaction processing**, including command handling and authorization
* **Platform abstraction layer** to run on any RTOS without code changes
* **Linux reference implementation** included with the SDK
* **Example application** to test your setup quickly

## System Overview

The Nayax Embedded solution includes three elements:

<Columns cols={3}>
  <Card title="Cashless Reader Hardware">
    The UNO-mini reader running EMV Core firmware, exposing a JSON Payment API and network socket interface.
  </Card>

  <Card title="SDK Sample Code">
    C99 sample code implementing the network socket and payment API calls.
  </Card>

  <Card title="Nayax Servers (Nayax Core)">
    Cloud service for remote terminal management and transaction clearing.
  </Card>
</Columns>

<Frame>
  <img src="https://mintcdn.com/nayax-44d6e37b/mqSvbg9R3CfdCY1b/images/docs/rtos-overview/system-overview.png?fit=max&auto=format&n=mqSvbg9R3CfdCY1b&q=85&s=78224b2d4308bb6f3978f5b7803f2853" width="998" height="447" data-path="images/docs/rtos-overview/system-overview.png" />
</Frame>

## Hardware and Software Architecture

The UNO-mini reader running EMV Core connects to the Host platform (MCU/RTOS) via UART TTL or USB HID.

<Frame>
  <img src="https://mintcdn.com/nayax-44d6e37b/mqSvbg9R3CfdCY1b/images/docs/rtos-overview/hw-sw-architecture.png?fit=max&auto=format&n=mqSvbg9R3CfdCY1b&q=85&s=eb18a2f451cc17e0407751eebe4faf0c" width="674" height="337" data-path="images/docs/rtos-overview/hw-sw-architecture.png" />
</Frame>

<Frame>
  <img src="https://mintcdn.com/nayax-44d6e37b/mqSvbg9R3CfdCY1b/images/docs/rtos-overview/hw-sw-architecture-2.png?fit=max&auto=format&n=mqSvbg9R3CfdCY1b&q=85&s=6042b64d50ff6d8f1c83ff36fcd59f5c" width="988" height="301" data-path="images/docs/rtos-overview/hw-sw-architecture-2.png" />
</Frame>

### Application Layers

Communication flows through the following layers:

| Layer                 | Description                                                             |
| :-------------------- | :---------------------------------------------------------------------- |
| **Application Layer** | Your code calls SDK APIs (e.g., `EcodSdk_PreAuthorize()`)               |
| **JSON-RPC Layer**    | Converts API calls to JSON-RPC messages with datalink framing           |
| **Serial Transport**  | Sends framed messages via UART (`/dev/ttyUSB0`) or HID (`/dev/hidraw0`) |
| **EMV Core Device**   | Processes payment requests and returns responses                        |
| **Callback System**   | Async responses delivered via registered callbacks                      |

## Requirements Summary

| Requirement           | Details                                       |
| :-------------------- | :-------------------------------------------- |
| **Device connection** | USB HID or UART TTL                           |
| **Minimum RAM**       | 64 KB (configurable for smaller systems)      |
| **Reader power**      | 5–12 VDC, 0.7 W idle / 3 W peak               |
| **Network**           | IPv4 TCP sockets, DNS resolution, client-only |
| **Compiler**          | GCC 4.8+ or Clang 3.5+ with C99 support       |

## Next Steps

<Columns cols={3}>
  <Card icon="link" title="Get Started" href="/docs/integrate-pos-device/emv-core/rtos/rtos-get-started">
    SDK delivery, firmware installation, and obtaining your Device ID.
  </Card>

  <Card icon="link" title="Integration Guide" href="/docs/integrate-pos-device/emv-core/rtos/rtos-integration-guide">
    Threading, callbacks, error handling, and configuration.
  </Card>

  <Card icon="link" title="C API Reference" href="/docs/integrate-pos-device/emv-core/rtos/rtos-c-api">
    Complete C API function reference and key data types.
  </Card>
</Columns>