Cutting Through the Confusion with ARM Cortex-M Interrupt Priorities
ARM Cortex-M interrupt priorities are famously confusing because numeric priority values are inverted relative to urgency and several different conventions coexist. This post cuts through the mess by explaining NVIC register bit placement, the CMSIS NVIC_SetPriority convention, preempt versus subpriority grouping, and when to use PRIMASK or BASEPRI. Read on for practical rules to avoid subtle priority bugs in real-time firmware.
Cortex-M Exception Handling (Part 2)
Exception entry and return on Cortex-M look simple, but the hardware does a lot to preserve context, enforce privilege, and pick the right stack. This post walks through the processor actions after an exception is accepted: which registers get pushed, how CONTROL, MSP and PSP affect stack selection, how EXC_RETURN encodes the return path, and why VTOR and vector table alignment matter for handler lookup.
Metal detection: beat frequency oscillator
Fabien Le Mentec walks through a practical beat frequency oscillator metal detector, from the LC oscillator theory to the Arduino-based frequency counter. He shows how changes in coil inductance reveal nearby metal, and why capacitor choice matters when you want a stable detector. The post focuses on the BFO sensing stage, with enough detail to help you build and test one yourself.
Analyzing the Linker Map file with a little help from the ELF and the DWARF
Running out of Flash or RAM is a familiar pain for firmware engineers, and the linker map only tells part of the story. This post shows how to combine the linker MAP with ELF symbol tables and DWARF debug info to recover static symbols, sizes, and source files that the map omits. It also describes a C# WinForms viewer that automates the parsing with binutils and helps you spot module and symbol-level memory waste.
Mounting plate for Arduino
While having a breadboard with your microcontroller is necessary, it is very cumbersome if the two aren't fastened together somehow. You can buy mounting plates, but I choose to make one.
Cortex-M Exception Handling (Part 1)
This article describes how Cortex-M processors handle interrupts and, more generally, exceptions, a concept that plays a central role in the design and implementation of most embedded systems.
Trust, but Verify: Examining the Output of an Embedded Compiler
Jason Sachs argues embedded engineers should read their compiler's assembly even if they rarely write assembly. He walks through Microchip XC16 output for dsPIC33 devices, showing how simple C variants and optimization flags produce very different code. The article demonstrates practical verification techniques and a tiny Python helper, pyxc16, to quickly inspect assembly for timing-sensitive firmware without rewriting everything in assembly.
Improving the Reload2 active load
Fabien Le Mentec takes a low-cost Reload2 active load and turns it into a programmable test tool. By swapping the manual setpoint for a Teensy 3.1 DAC and replacing the op-amp with a chopper amplifier, he gets software-controlled current profiles and lowers the minimum load current to about 7 mA. It is a practical hack for testing power supplies and Ethernet-powered boards under realistic startup and sleep conditions.
Slew Rate Limiters: Nonlinear and Proud of It!
Slew-rate limits are a small nonlinear detail that often decides whether a controller behaves nicely or wrecks hardware. Jason Sachs walks through why slew limits appear in electronics and actuators, then shows two practical digital ways to impose limits: constraining input increments and constraining input around the output. He compares performance on underdamped second-order systems, gives closed-form intuition for overshoot, and demonstrates simulations with scipy and ODE solvers.
Introduction to Microcontrollers - 7-segment displays & Multiplexing
Seven-segment displays can eat dozens of GPIO pins and dozens of resistors, but multiplexing trades pins for time and cuts component count dramatically. Mike Silva shows a hands-on AVR C implementation with segment encoding, a 100 Hz display scan ISR, several integer-to-digit conversion techniques, and software workarounds for messy pin mappings. He also demonstrates a timer "leapfrog" to reuse one timer for two tasks and compares performance so you can choose the best approach for your MCU.
Introduction to Microcontrollers - More Timers and Displays
Mike Silva walks through using a single hardware timer to create the illusion of parallel tasks, combining a millisecond tick, deadline checks, and a cyclic executive to run time-driven and event-driven work. He shows safe deadline code that handles timer rollover and ISR races, and provides practical STM32 examples including SysTick-driven delays, atomic GPIO BSRR writes for LCD control, and a button-driven display demo.
STM32 VS Code Extension Under The Hood
ST's STM32 VS Code extension hides useful CMake projects and VS Code tasks behind a friendly UI, but understanding what it generates lets you bend it to your needs. This video peels back the layers to show the generated CMake files, how to modify them, how to add a VS Code-invokable flash task, and how to enable C++ support alongside C. The STM32 F0 example and flash task are available on GitHub.
Arduino robotics #2 - chassis, locomotion and power
Lonnie Honeycutt walks through building Clusterbot's round differential-drive chassis, showing how a circular base and Tamiya gearbox simplify turning and torque tradeoffs. The post covers motor selection, wheel fit, balance issues, and a practical two-battery power arrangement with VMOT for the motors and a separate 9V for the Arduino. Expect hands-on tips and lessons learned from a first-time robot build.
3 Overlooked Embedded Software Elements
Jacob Beningo points out three often-overlooked elements that can make embedded projects less painful and faster to ship. He highlights model-generated code for off-target iteration, configuration-generated code to manage SKUs and avoid fragile conditional compilation, and automated test harnesses to catch regressions early. The post gives practical reasons to consider each approach and how they fit into modern embedded DevOps.
Arduino robotics #3 - wiring, coding and a test run
Lonnie Honeycutt walks through wiring, coding, and the first test run of Clusterbot, a budget Arduino robot build costing about $50. The post provides a clear pin-mapping to the TB6612FNG motor driver, ready-to-upload Arduino movement functions, and practical tips like tinning thin battery wires. You also get PWM calibration values and the measured RPM timing the author used to make reliable turns.
Arduino robotics #4 - HC-SR04 ultrasonic sensor
Lonnie Honeycutt shows how to turn a $50 mobile platform into a simple autonomous robot by adding an HC-SR04 ultrasonic sensor to an Arduino. The post walks through wiring, a minimal test sketch and the integration code used on Clusterbot, plus practical tips on range limits, motor choices and library options to make obstacle avoidance reliable for hobby builds.
Introduction to Microcontrollers - Button Matrix & Auto Repeating
Wiring every button to its own GPIO gets expensive fast, so Mike Silva shows how to read a 4x4 keypad with only eight pins using matrix scanning. He then builds the raw scan into a debounced state machine, adds auto-repeat, and even extends it to a two-stage repeat rate. The result is a practical, code-heavy walkthrough for turning a keypad into clean button events on AVR and STM32.
My friend, the compiler
Modern compilers were given great powers, but we don't always know where and when they'll use them. This may cause us to either worry needlessly or trust unjustifiably, as demonstrated by a little example in this post.
OOKLONE: a cheap RF 433.92MHz OOK frame cloner
Fabien Le Mentec built a pocket device that listens to and clones 433.92MHz OOK frames, automating the tedious reverse engineering of cheap wireless outlets. The prototype uses a Moteino with an RFM69 to sample demodulated OOK data, stores pulse durations in SRAM, and replays frames; the code and hardware notes are available on GitHub along with limitations and next steps.
Introduction to Deep Insight Analysis for RTOS Based Applications
Debugging can consume over 40% of a development cycle, and Jacob Beningo argues RTOS projects need more than breakpoints and assertions. He presents deep insight analysis as a trio of techniques—RTOS-aware debugging, run-time analysis, and profiling with coverage—that expose what the system is actually doing. These methods help engineers cut guesswork and speed verification of complex embedded applications.
Are We Shooting Ourselves in the Foot with Stack Overflow?
Most traditional, beaten-path memory layouts allocate the stack space above the data sections in RAM, even though the stack grows “down” (towards the lower memory addresses) in most embedded processors. This arrangement puts your program data in the path of destruction of a stack overflow. In other words, you violate the first Gun Safety Rule (ALWAYS keep the gun pointed in a safe direction!) and you end up shooting yourself in the foot. This article shows how to locate the stack at the BEGINNING of RAM and thus point it in the "safe" direction.
Learning A New Microcontroller
Learning a new microcontroller becomes manageable with a repeatable, stepwise process that focuses on common peripherals, tools, and example programs. This post lays out hands-on exercises from blinky and UART echoes through I2C/SPI, PWM and ADC to DMA and RTOS variations, and shows how to evolve prototype code into reusable HAL and OSAL layers. Practical tips cover hardware setup, logic analyzers, and keeping an engineering notebook.
Trust, but Verify: Examining the Output of an Embedded Compiler
Jason Sachs argues embedded engineers should read their compiler's assembly even if they rarely write assembly. He walks through Microchip XC16 output for dsPIC33 devices, showing how simple C variants and optimization flags produce very different code. The article demonstrates practical verification techniques and a tiny Python helper, pyxc16, to quickly inspect assembly for timing-sensitive firmware without rewriting everything in assembly.
Understanding Microchip 8-bit PIC Configuration
The second post of a five part series picks up getting started developing with Microchip 8-bit PIC Microcontroller by examining the how and why of processor configuration. Topics discussed include selecting the oscillator to use during processor startup and refining the configuration once the application starts. A walk through of the code generated by the Microchip IDE provides a concrete example of the specific Configuration Word and SFR values needed to configure the project specific clock configuration.
Getting Started With Zephyr: Saving Data To Files
In this blog post, I show how to implement a Zephyr application to mount a microSD card, create a new file on the microSD card, and write data to it. The lessons learned from such an application can be helpful for devices out in the field that need to write data to off-board memory periodically, especially in cases where Internet access may be sporadic.
Cutting Through the Confusion with ARM Cortex-M Interrupt Priorities
ARM Cortex-M interrupt priorities are famously confusing because numeric priority values are inverted relative to urgency and several different conventions coexist. This post cuts through the mess by explaining NVIC register bit placement, the CMSIS NVIC_SetPriority convention, preempt versus subpriority grouping, and when to use PRIMASK or BASEPRI. Read on for practical rules to avoid subtle priority bugs in real-time firmware.
Arduino robotics #3 - wiring, coding and a test run
Lonnie Honeycutt walks through wiring, coding, and the first test run of Clusterbot, a budget Arduino robot build costing about $50. The post provides a clear pin-mapping to the TB6612FNG motor driver, ready-to-upload Arduino movement functions, and practical tips like tinning thin battery wires. You also get PWM calibration values and the measured RPM timing the author used to make reliable turns.
Working with Microchip PIC 8-bit GPIO
The third in a series of five posts looks at GPIO with PIC 8-bit microcontrollers. After a detailed review of the registers for configuring and managing GPIO on the PIC18F47Q10 processor, a basic application is stood up programming those registers to blink external LEDs at 0.5Hz.
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.
Choosing a Microcontroller for Your Vehicle
Picking the right microcontroller can make or break an autonomous vehicle project, and this post gives a practical checklist to help. It walks through voltage and power needs, memory and IO planning, cost and availability tradeoffs, and when to step up from an 8-bit MCU to a 32-bit controller or single-board computer. Real-world board examples illustrate the choices.
