Banknote Sensor RTOS

This project is a real-time embedded application implementing a simplified banknote authentication pipeline.

It is developed and executed in a RTOS environment, running on a host-based target for fast iteration. The execution model, constraints, and failure modes are those of a microcontroller-class system; only the physical sensors are abstracted during development.

The application is structured exactly as it would be for deployment on real hardware.

Scope

What this project does:

• Implements a real-time, multi-stage pipeline
• Uses strict RTOS primitives: threads, priorities, timers, bounded queues
• Enforces embedded constraints
• Simulates sensor inputs while keeping the application logic unchanged

This project doesnt replicate accuratly the electrical environement, is it made first to display the architecture and structure needed in a similar realistic context.

Project logic structure

---
title: Banknote Sensor Pipeline
---
flowchart TD
  subgraph SIM["Hardware Simulation"]
    subgraph TIM["Running on k_timer"]
      VIS_SENSOR["VIS Sensor"]
      UV_SENSOR["UV Sensor"]
    end
    VIS_SENSOR-- Filling on fixed interval -->VIS_SENSOR_BUF["VIS Sensor hardware memory"]
    UV_SENSOR-- Filling on fixed interval -->UV_SENSOR_BUF["UV Sensor hardware memory"]
  end
  VIS_SENSOR_BUF-- Simulate IRQ signal -->ISR
  UV_SENSOR_BUF-- Simulate IRQ signal -->ISR

ISR["ISR"]-- non blocking filling with just sensor id -->PCKQ["k_msgq of sensor id"]

  subgraph THR["Thread Context"]
    subgraph HND["Handler thread - priority 1"]
      HANDLER["Handler task"]-- thread wait for k_msgq to have data -->PCKQ
      HANDLER-- Retreive data from hardware memeory -->SENSOR_BUF["VIS or UV Sensor hardware memory"]
      HANDLER-- Fill with timestamp data and sensor id -->SMPLQ["Sample queue"]
    end
    subgraph PROC["Process thread  - priority 2"]
      PROCESSING["Processing Task"]-- thread wait for k_msgq to have data -->SMPLQ
      PROCESSING-- handle samples and comes to a conclusion -->DECISION["SUCCESS | INCONCLUSIVE | FAIL"]
    end
    subgraph MON["Monitoring thread - priority 3"]
      MONITORING["Monitoring task, every second gather all the atomic counters and print log"]
      MONITORING-->HANDLER
      MONITORING-->PROCESSING
    end
  end

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Execution Environment

• RTOS: Zephyr RTOS
• Target: native_sim (host-based execution for development and CI)
• Host OS: Linux

The same application can later be built for real microcontroller targets without structural changes.

Repository Model

This repository is application-only.

It contains:

• application source code
• RTOS configuration
• a manifest pinning external dependencies

It does not contain:

• the RTOS source tree
• external modules
• build artifacts
• toolchains or SDKs

All external components are fetched and managed by the workspace tooling.

Build Environment

Host

• Linux
• Python ≥ 3.10
• CMake, Ninja
• RTOS SDK

Target

• Host-based RTOS execution (native_sim)

Build and Run

Initialize the workspace and fetch dependencies:

west init -m <repo-url>
cd <workspace>
west update
west zephyr-export

Build:

west build -b native_sim .

Run:

./build/zephyr/zephyr.exe