Finite State Machines (FSM) in Embedded Systems (Part 4) - Let 'em talk
No state machine is an island. State machines do not exist in a vacuum, they need to "talk" to their environment and each other to share information and provide synchronization to perform the system functions. In this conclusive article, you will find what kind of problems and which critical areas you need to pay attention to when designing a concurrent system. Although the focus is on state machines, the consideration applies to every system that involves more than one execution thread.
Five Embedded Linux Topics for Newbies !
Are you an embedded systems enthusiast looking to broaden your horizons with embedded Linux? explore those 5 topics.
You Don't Need an RTOS (Part 2)
In this second article, we'll tweak the simple superloop in three critical ways that will improve it's worst-case response time (WCRT) to be nearly as good as a preemptive RTOS ("real-time operating system"). We'll do this by adding task priorities, interrupts, and finite state machines. Additionally, we'll discuss how to incorporate a sleep mode when there's no work to be done and I'll also share with you a different variation on the superloop that can help schedule even the toughest of task sets.
A design non-methodology
Although writing an RTOS or kernel may be an interesting project, it is unlikely to be a wise course of action.
How to use I2C devices in (Apache) NuttX: Scanning for Devices
Hands-on guide to scanning I2C peripherals on NuttX using a Raspberry Pi Pico, showing how the RTOS exposes i2c master instances and the i2ctool. The article walks through where the RP2040 I2C driver lives, how to enable I2C0 in menuconfig, build and flash nuttx, and run the i2c dev command to probe the bus. Verify sensors like BMP280 or SSD1306 before registering drivers.
You Don't Need an RTOS (Part 1)
In this first article, we'll compare our two contenders, the superloop and the RTOS. We'll define a few terms that help us describe exactly what functions a scheduler does and why an RTOS can help make certain systems work that wouldn't with a superloop. By the end of this article, you'll be able to: - Measure or calculate the deadlines, periods, and worst-case execution times for each task in your system, - Determine, using either a response-time analysis or a utilization test, if that set of tasks is schedulable using either a superloop or an RTOS, and - Assign RTOS task priorities optimally.
Using (Apache) NuttX Buttons Subsystem
You do not need to poke GPIO registers to read switches in NuttX, the OS provides a Buttons subsystem that delivers named events, multi-button support, and optional software debouncing. This post walks through wiring two breadboard buttons on a Raspberry Pi Pico, enabling the input and buttons drivers via menuconfig, building nuttx.uf2, and testing the buttons over the usbnsh serial console. It highlights why a simple hardware debounce is still a good idea.
BusyBox; The Swiss Army Knife of Embedded Linux
In this article we cover the BusyBox, how it's designed to be optimized for embedded targets, and how to configure and build it in different ways, we also covered the license and limitation, which led to the development of ToyBox, I hope you enjoyed the article, please leave a comment for any correction or suggestions.
Using (Apache) NuttX USERLED Subsystem
Controlling an LED with raw GPIO works, but NuttX's USERLED subsystem makes it cleaner and portable. This post walks through enabling the LED driver in menuconfig, mapping the RaspberryPi Pico LED in the board files, and using the /dev/userleds device with printf to set up to 32 LEDs with a single write. It finishes with a hands-on challenge to expand the setup to eight LEDs on a breadboard.
Using the Beaglebone PRU to achieve realtime at low cost
Fabien Le Mentec shows how the BeagleBone Black's PRU coprocessors can run hard realtime control loops, removing the need for an FPGA or dedicated microcontroller. He walks through Linux setup, device tree enabling, assembler and loader tools, and a timer example that reads ADCs and drives PWM from PRU code. The post highlights community SDKs and a recent TI Code Composer Studio option for C-based PRU development.
Mutex vs. Semaphore - Part 1
Most forum answers get the semaphore versus mutex debate wrong. This post traces semaphores back to Dijkstra and Scholten, explains the difference between binary and counting semaphores, and highlights runtime hazards such as accidental release, recursive and task-death deadlocks, priority inversion, and misuse as signals. Read if you want to avoid common concurrency pitfalls in RTOS code.
Getting Started With Zephyr: DTS vs DTSI vs Overlays
Devicetrees can be daunting for traditional embedded software engineers that are new to Zephyr. In this blog post, I address these fears and show how navigating Devicetrees can be much easier if you understand that they represent the layered structure of the underlying hardware.
From Baremetal to RTOS: A review of scheduling techniques
Jacob Beningo walks through five common embedded scheduling techniques, showing how each scales from a single super loop to a full RTOS. He highlights practical trade-offs for round-robin, interrupt-driven, queued, cooperative, and RTOS approaches so you can spot when timing becomes fragile and when added complexity is justified. This primer sets up the next post on when to adopt an RTOS.
Modern Embedded Systems Programming: Beyond the RTOS
Blocking-based RTOS tasks make embedded systems brittle and hard to extend, this post argues, and presents a practical alternative: active objects organized as message pumps. It explains why one-blocking-call tasks and nonblocking event handlers improve responsiveness and reduce task proliferation, and recommends using frameworks plus hierarchical state machines and UML to enforce good architecture and make designs scalable.
Getting Started with NuttX RTOS on Three Low Cost Boards
You can get Linux-like power on cheap microcontroller boards using NuttX, not a full Linux system. This article walks through building and flashing NuttX on three low-cost targets: Raspberry Pi Pico (RP2040), ESP32-DevKitC, and STM32F4Discovery, covering SDKs, toolchains, and serial access. Follow the provided commands to configure, compile, and connect to the NuttShell so you can start experimenting with NuttX quickly.
Examining The Stack For Fun And Profit
Stack bloat can hide in short initialization paths, and this post walks through finding it with hands-on debugging. The author builds a tiny test program and uses gdb plus custom stack-helper scripts to scan, watch, and walk the stack. That process reveals getaddrinfo pulling in glibc DNS code that allocates large local buffers and uses alloca and PLT resolution, consuming roughly 11KB of stack.
Blocking == Technical Debt
Blocking code in embedded systems trades quick development for long-term pain, effectively becoming technical debt. This post shows how blocking in Arduino examples and traditional RTOS threads hard-codes sequences and timing, making change and extension expensive. It contrasts blocking kernels with preemptive non-blocking approaches and recommends event-driven Active Objects and frameworks like QP as more scalable alternatives.
Delayed printf for real-time logging
Yossi Kreinin demonstrates delayed printf, a technique that records printf format pointers and raw argument words into a compact buffer so logging does not disturb real-time timing. He walks through a small C++11 writer using variadic templates and an atomic buffer plus a gdb Python reader that reconstructs formatted messages from executables or core dumps. The result is readable post-processed logs with minimal runtime overhead.
Getting Started With Zephyr: Devicetree Bindings
This blog post shines some light on how devicetrees are used in The Zephyr Project. Specifically, we understand the mechanisms that enable us to use nodes in the devicetree in the C source files. We use a sample provided in the Zephyr repository itself and work our way through portions of the Zephyr codebase to get insight into the mechanisms that make this possible.
Mutex vs. Semaphores – Part 2: The Mutex & Mutual Exclusion Problems
Mutexes tackle many semaphore pitfalls by enforcing ownership and pairing lock and unlock operations, making mutual exclusion safer in RTOS code. This post explains how ownership enables recursion, priority inheritance and death detection, and why mutexes do not automatically solve circular deadlock or non-cooperative access. Read on for practical protocols such as Priority Inheritance and Priority Ceiling and a brief note on monitors.
You Don't Need an RTOS (Part 2)
In this second article, we'll tweak the simple superloop in three critical ways that will improve it's worst-case response time (WCRT) to be nearly as good as a preemptive RTOS ("real-time operating system"). We'll do this by adding task priorities, interrupts, and finite state machines. Additionally, we'll discuss how to incorporate a sleep mode when there's no work to be done and I'll also share with you a different variation on the superloop that can help schedule even the toughest of task sets.
Libgpiod - Toggling GPIOs The Right Way In Embedded Linux
Accessing GPIOs through sysfs is simple but fragile, causing race conditions when multiple userspace processes touch the same line. This post explains libgpiod, introduced in Linux 4.8, and shows concise Python examples on a Toradex Verdin iMX8M Plus for requesting lines, tagging the consumer, using active_low flags, and reading or driving values. Learn why libgpiod provides safer, atomic GPIO handling.
Finite State Machines (FSM) in Embedded Systems (Part 4) - Let 'em talk
No state machine is an island. State machines do not exist in a vacuum, they need to "talk" to their environment and each other to share information and provide synchronization to perform the system functions. In this conclusive article, you will find what kind of problems and which critical areas you need to pay attention to when designing a concurrent system. Although the focus is on state machines, the consideration applies to every system that involves more than one execution thread.
How to make a heap profiler
A heap profiler is surprisingly simple to build, and Yossi Kreinin walks through a compact working example called heapprof. The post shows how to intercept malloc/free, stash per-allocation metadata and call stacks into heap chunks, dump memory on crash or via JTAG, and map return addresses to source lines with addr2line or gdb. It also covers practical bootstrapping tricks for platforms without standard libc support.
Round-robin or RTOS for my embedded system
Manuel Herrera walks through the practical tradeoffs between bare-metal round-robin loops and adopting an RTOS for embedded projects. He outlines two round-robin styles, explains how an RTOS gives independent threads and synchronization primitives, and highlights added code, licensing, interrupt latency, and the learning curve. Read this to sharpen decision criteria around timing guarantees, reuse, and whether an RTOS truly adds value to your firmware.
How to Achieve Deterministic Behavior in Real-Time Embedded Systems
Ensuring deterministic behavior in real-time embedded systems is paramount for their reliability and performance. The ability to predict precisely how a system will respond to various inputs at any given time is crucial in critical applications such as medical devices, aerospace systems, and automotive safety mechanisms. Achieving deterministic behavior involves meticulous design, stringent testing, and adherence to strict timing constraints.
Linux Kernel Development - Part 1: Hello Kernel!
Skip userland and run code inside the kernel with a tiny "Hello Kernel" module that prints messages on load and unload. This introduction walks through required headers, the init and exit hooks, MODULE_* metadata, a kernel-friendly Makefile, and the basic workflow to build, insmod, rmmod and inspect messages with dmesg. It’s a hands-on first step into Linux kernel module development.
Understanding Yocto Project Layers: A Modular Approach to Embedded Systems Development
Managing metadata across embedded Linux builds gets messy fast, so the Yocto Project uses layers to keep things modular and reusable. This post walks through inspecting active layers with bitbake-layers, controlling overrides with BBFILE_PRIORITY, and creating a meta-yocto-splash-img layer that uses a .bbappend to replace psplash. It finishes by showing how to verify the custom splash screen in QEMU so you can test safely before deploying to hardware.
Getting Started With Zephyr: Kconfig
In this blog post, we briefly look at Kconfig, one of the core pieces of the Zephyr infrastructure. Kconfig allows embedded software developers to turn specific subsystems on or off within Zephyr efficiently and control their behavior. We also learn how we can practically use Kconfig to control the features of our application using the two most common mechanisms.
