https://embeddedera.com/notes/ Notes from the bench on PCB design, firmware, and obsolete-part redesign — practical, written by the engineer who does the work. en-US Sat, 31 Oct 2026 00:00:00 GMT https://embeddedera.com/notes/why-a-load-cell-reading-drifts-with-an-hx711/ https://embeddedera.com/notes/why-a-load-cell-reading-drifts-with-an-hx711/ Sat, 31 Oct 2026 00:00:00 GMT Why load cell readings creep or jump with an HX711, and the wiring, reference, filtering and calibration checks that separate real drift from noise. pcb-design design-for-test firmware https://embeddedera.com/notes/why-a-current-monitor-reads-wrong-at-1-ma/ https://embeddedera.com/notes/why-a-current-monitor-reads-wrong-at-1-ma/ Fri, 30 Oct 2026 00:00:00 GMT Why an INA226-class shunt monitor misreads small currents, how to size the shunt, and when to switch ranges or measure sleep current another way. design-for-test pcb-design firmware https://embeddedera.com/notes/why-an-e-paper-display-ghosts-after-partial-refresh/ https://embeddedera.com/notes/why-an-e-paper-display-ghosts-after-partial-refresh/ Thu, 29 Oct 2026 00:00:00 GMT Why e-paper ghosts after repeated partial refreshes, what the vendor docs say to do about it, and the firmware rules that keep the panel readable and healthy. firmware pcb-design https://embeddedera.com/notes/why-a-thermocouple-reading-is-off-by-a-few-degrees/ https://embeddedera.com/notes/why-a-thermocouple-reading-is-off-by-a-few-degrees/ Wed, 28 Oct 2026 00:00:00 GMT Where cold-junction error comes from on a thermocouple input, how to place the sensor and connector, and what to check before you trust the reading. pcb-design layout design-for-test https://embeddedera.com/notes/why-a-pt100-or-pt1000-reading-is-wrong-by-a-degree-or-two/ https://embeddedera.com/notes/why-a-pt100-or-pt1000-reading-is-wrong-by-a-degree-or-two/ Tue, 27 Oct 2026 00:00:00 GMT How lead wires, a drifting excitation current and the reference resistor throw off an RTD reading, and the front-end checks that fix each one. pcb-design layout design-for-test https://embeddedera.com/notes/why-a-humidity-sensor-reads-wrong-inside-an-enclosure/ https://embeddedera.com/notes/why-a-humidity-sensor-reads-wrong-inside-an-enclosure/ Mon, 26 Oct 2026 00:00:00 GMT Why humidity and temperature sensors read off once the case is closed, and the placement, venting, duty-cycle and test checks that fix it before tooling. pcb-design layout manufacturing https://embeddedera.com/notes/why-a-usb-c-board-works-on-usb-a-but-not-c-to-c/ https://embeddedera.com/notes/why-a-usb-c-board-works-on-usb-a-but-not-c-to-c/ Sun, 25 Oct 2026 00:00:00 GMT Why a board powers from a USB-A to C cable but dies on C-to-C, plus the CC resistor, receptacle and bench checks that find the cause before respinning. usb-c pcb-design design-for-test https://embeddedera.com/notes/why-a-boost-converter-fails-when-the-wi-fi-radio-starts/ https://embeddedera.com/notes/why-a-boost-converter-fails-when-the-wi-fi-radio-starts/ Sat, 24 Oct 2026 00:00:00 GMT Why a battery ESP32 design browns out or kills its boost converter at Wi-Fi transmit, and the inductor, capacitor and layout checks that find it. pcb-design layout power-delivery https://embeddedera.com/notes/swapping-an-out-of-stock-part-without-missing-a-pin/ https://embeddedera.com/notes/swapping-an-out-of-stock-part-without-missing-a-pin/ Fri, 23 Oct 2026 00:00:00 GMT A checklist for replacing a sold-out IC on a finished board: pinout, quiescent current, output capacitors, land pattern and what to test before you rebuild. obsolescence pcb-design eol https://embeddedera.com/notes/reverse-polarity-protection-for-a-dc-power-input/ https://embeddedera.com/notes/reverse-polarity-protection-for-a-dc-power-input/ Thu, 22 Oct 2026 00:00:00 GMT Series diode, P-channel MOSFET or ideal-diode controller: what each costs the board, and the datasheet checks that stop a wrong plug from killing it. pcb-design power-delivery design-for-test https://embeddedera.com/notes/debugger-can-t-connect-to-a-new-board-over-swd/ https://embeddedera.com/notes/debugger-can-t-connect-to-a-new-board-over-swd/ Wed, 21 Oct 2026 00:00:00 GMT A short checklist for 'no target found' on a custom ARM board: power, wiring, reset, sleeping firmware and locked chips, plus what to put on the PCB. firmware design-for-test pcb-design https://embeddedera.com/notes/membrane-switch-overlay-design-checklist/ https://embeddedera.com/notes/membrane-switch-overlay-design-checklist/ Tue, 20 Oct 2026 00:00:00 GMT What to settle before a membrane switch overlay goes to a fabricator: tail exit, venting, domes, material, shielding and enclosure fit, with reasons. pcb-design manufacturing design-for-test https://embeddedera.com/notes/i2c-bus-stuck-low-after-a-reset/ https://embeddedera.com/notes/i2c-bus-stuck-low-after-a-reset/ Mon, 19 Oct 2026 00:00:00 GMT Why an I2C sensor holds SDA low after the MCU resets, how the nine-clock bus clear works, and the board and firmware changes that prevent a hang. firmware design-for-test pcb-design https://embeddedera.com/notes/why-a-crystal-oscillator-won-t-start-or-runs-off-frequency/ https://embeddedera.com/notes/why-a-crystal-oscillator-won-t-start-or-runs-off-frequency/ Sun, 18 Oct 2026 00:00:00 GMT How to pick load capacitors, check startup margin and layout for an MCU crystal, so the board boots every time and the clock stays on frequency. pcb-design layout design-for-test https://embeddedera.com/notes/where-to-put-esd-protection-on-a-usb-or-connector-port/ https://embeddedera.com/notes/where-to-put-esd-protection-on-a-usb-or-connector-port/ Fri, 16 Oct 2026 00:00:00 GMT Where the TVS diode goes next to the connector, how to ground it with short stitched vias, and what to keep out of the path so a static zap at the connector… pcb-design layout compliance https://embeddedera.com/notes/setting-a-lead-free-reflow-profile-from-the-paste-datasheet/ https://embeddedera.com/notes/setting-a-lead-free-reflow-profile-from-the-paste-datasheet/ Thu, 15 Oct 2026 00:00:00 GMT How to turn a solder paste datasheet into an oven profile, where to put thermocouples, and which defect points at which part of the curve. manufacturing pcb-design https://embeddedera.com/notes/first-power-up-of-a-new-prototype-board-step-by-step/ https://embeddedera.com/notes/first-power-up-of-a-new-prototype-board-step-by-step/ Wed, 14 Oct 2026 00:00:00 GMT A bring-up order that finds shorts, bad rails and dead debug links before they cost you a board: what to check on a current-limited bench supply, in what… design-for-test pcb-design firmware https://embeddedera.com/notes/writing-the-software-for-a-production-test-fixture/ https://embeddedera.com/notes/writing-the-software-for-a-production-test-fixture/ Tue, 13 Oct 2026 00:00:00 GMT What a functional test script should do on a small production run: program, verify, measure, log, and fail loudly. Existing open-source tools to build on. design-for-test test-fixtures manufacturing https://embeddedera.com/notes/what-test-points-and-programming-pads-a-board-needs/ https://embeddedera.com/notes/what-test-points-and-programming-pads-a-board-needs/ Mon, 12 Oct 2026 00:00:00 GMT Which signals to bring out for programming, debug and production test, so a board can be flashed and checked on a fixture without a respin. design-for-test test-fixtures firmware https://embeddedera.com/notes/checking-kicad-fabrication-files-before-you-send-them/ https://embeddedera.com/notes/checking-kicad-fabrication-files-before-you-send-them/ Sun, 11 Oct 2026 00:00:00 GMT A pre-release check for KiCad Gerbers, drill files, BOM and placement data, so the fab or assembler doesn't email back with questions or build the wrong board. kicad manufacturing pcb-design https://embeddedera.com/notes/ble-module-or-chip-down-for-a-new-product/ https://embeddedera.com/notes/ble-module-or-chip-down-for-a-new-product/ Sat, 10 Oct 2026 00:00:00 GMT How to decide between a certified Bluetooth LE module and a bare SoC: what each choice does to certification, antenna work, supply and schedule. pcb-design compliance https://embeddedera.com/notes/finding-why-a-device-resets-in-the-field/ https://embeddedera.com/notes/finding-why-a-device-resets-in-the-field/ Tue, 06 Oct 2026 00:00:00 GMT How to read the reset-cause register, capture a fault record before reboot, and tell a power problem from a firmware bug on STM32, ESP32 and nRF52. firmware design-for-test https://embeddedera.com/notes/when-smt-parts-that-sat-open-need-baking-before-reflow/ https://embeddedera.com/notes/when-smt-parts-that-sat-open-need-baking-before-reflow/ Sun, 04 Oct 2026 00:00:00 GMT How to tell whether an opened reel or tray of moisture-sensitive parts is still safe to reflow, why popcorning happens, and what a bake resets. manufacturing pcb-design https://embeddedera.com/notes/when-a-pcb-needs-conformal-coating/ https://embeddedera.com/notes/when-a-pcb-needs-conformal-coating/ Sat, 03 Oct 2026 00:00:00 GMT How to decide if a board needs coating, which chemistry to pick, and what coating does to test, rework and the layout you hand the assembler. manufacturing pcb-design design-for-test https://embeddedera.com/notes/moving-a-legacy-altium-or-eagle-design-into-kicad/ https://embeddedera.com/notes/moving-a-legacy-altium-or-eagle-design-into-kicad/ Fri, 02 Oct 2026 00:00:00 GMT What KiCad's importers convert, what they silently drop, the checks that prove the new files match the old board, and what to export before a license dies. kicad pcb-design obsolescence https://embeddedera.com/notes/when-a-chip-revision-changes-but-the-part-number-doesn-t/ https://embeddedera.com/notes/when-a-chip-revision-changes-but-the-part-number-doesn-t/ Thu, 01 Oct 2026 00:00:00 GMT How to read a die-revision PCN, find the silicon revision in firmware and on the package, and decide what to requalify before new parts ship. obsolescence firmware manufacturing https://embeddedera.com/notes/provisioning-serial-numbers-and-keys-on-the-production-line/ https://embeddedera.com/notes/provisioning-serial-numbers-and-keys-on-the-production-line/ Wed, 30 Sep 2026 00:00:00 GMT Where per-unit serials, keys and debug locks go on STM32, nRF52 and ESP32, what is irreversible, and how to plan the programming step. firmware manufacturing security https://embeddedera.com/notes/checking-a-chip-s-longevity-commitment-before-you-design-it/ https://embeddedera.com/notes/checking-a-chip-s-longevity-commitment-before-you-design-it/ Tue, 29 Sep 2026 00:00:00 GMT How to read ST, NXP, TI, Microchip and Nordic longevity programs, what each one actually promises, and the checks to run before a part goes on the schematic. obsolescence eol pcb-design https://embeddedera.com/notes/adding-a-rechargeable-lithium-cell-to-a-product/ https://embeddedera.com/notes/adding-a-rechargeable-lithium-cell-to-a-product/ Mon, 28 Sep 2026 00:00:00 GMT The charger, protection and gauge a lithium-powered product needs on the board, what to ask the cell supplier for, and what to test before it ships. pcb-design firmware compliance https://embeddedera.com/notes/pcb-layout-mistakes-that-only-show-up-at-assembly/ https://embeddedera.com/notes/pcb-layout-mistakes-that-only-show-up-at-assembly/ Sun, 27 Sep 2026 00:00:00 GMT Fiducials, courtyards, polarity marks, panels and placement files: the layout details an SMT line trips on, and how to check each one before you send the job. pcb-design manufacturing layout https://embeddedera.com/notes/choosing-between-bare-metal-and-an-rtos-on-a-small-mcu/ https://embeddedera.com/notes/choosing-between-bare-metal-and-an-rtos-on-a-small-mcu/ Wed, 23 Sep 2026 00:00:00 GMT How to decide when a superloop is enough, what an RTOS actually costs in RAM and debugging effort, and the checks to run before you commit to one. firmware security https://embeddedera.com/notes/how-to-design-a-firmware-update-that-cannot-brick-the-device/ https://embeddedera.com/notes/how-to-design-a-firmware-update-that-cannot-brick-the-device/ Wed, 23 Sep 2026 00:00:00 GMT Plan firmware updates around recovery: image validation, rollback, application confirmation, compatible data, and failure tests on shipped hardware. firmware security https://embeddedera.com/notes/second-sourcing-the-spi-flash-on-a-microcontroller-board/ https://embeddedera.com/notes/second-sourcing-the-spi-flash-on-a-microcontroller-board/ Wed, 23 Sep 2026 00:00:00 GMT A practical review of SPI NOR flash substitutions: check the package, boot path, driver behavior, programming tools, and qualification evidence. obsolescence firmware eol https://embeddedera.com/notes/what-to-send-for-a-pcb-assembly-quote/ https://embeddedera.com/notes/what-to-send-for-a-pcb-assembly-quote/ Wed, 23 Sep 2026 00:00:00 GMT Prepare a clear PCB assembly quote package: fabrication data, a parts list, placement files, drawings, quantities, and revision checks before upload. pcb-design manufacturing https://embeddedera.com/notes/browser-based-firmware-flashing-without-an-installer/ https://embeddedera.com/notes/browser-based-firmware-flashing-without-an-installer/ Tue, 22 Sep 2026 00:00:00 GMT Check whether Web Serial or WebUSB can replace your firmware installer, which browsers support the workflow, and what drivers and recovery paths remain. firmware design-for-test manufacturing https://embeddedera.com/notes/ceramic-capacitor-long-lead-time-substitution/ https://embeddedera.com/notes/ceramic-capacitor-long-lead-time-substitution/ Mon, 21 Sep 2026 00:00:00 GMT The checks that decide whether a backordered ceramic capacitor can be swapped: DC bias, dielectric, voltage rating, ESR, height and board flex. obsolescence pcb-design manufacturing https://embeddedera.com/notes/sleep-current-higher-than-datasheet/ https://embeddedera.com/notes/sleep-current-higher-than-datasheet/ Sun, 20 Sep 2026 00:00:00 GMT The usual causes of sleep current far above the datasheet figure: debug probes, pins, pull-ups, regulators, sensors, and a bench method to find them. firmware pcb-design design-for-test https://embeddedera.com/notes/ble-provisioning-for-devices-with-no-screen/ https://embeddedera.com/notes/ble-provisioning-for-devices-with-no-screen/ Sat, 19 Sep 2026 00:00:00 GMT How to get Wi-Fi credentials onto a screenless BLE device: what pairing really protects, per-device secrets, phone quirks, and failure paths to design. firmware security https://embeddedera.com/notes/reverse-engineering-a-board-with-no-schematic/ https://embeddedera.com/notes/reverse-engineering-a-board-with-no-schematic/ Fri, 18 Sep 2026 00:00:00 GMT What it actually takes to turn a bare circuit board into a working schematic and BOM, and when the process is worth starting. obsolescence pcb-design reverse-engineering https://embeddedera.com/notes/kicad-autorouter-when-it-works/ https://embeddedera.com/notes/kicad-autorouter-when-it-works/ Thu, 17 Sep 2026 00:00:00 GMT What FreeRouting and newer GPU autorouters actually handle well in KiCad, where manual routing still wins, and the checks to run before trusting either. pcb-design kicad layout https://embeddedera.com/notes/pogo-pin-test-fixture-design/ https://embeddedera.com/notes/pogo-pin-test-fixture-design/ Wed, 16 Sep 2026 00:00:00 GMT Pin choice, tip style, pitch, and alignment decisions that determine whether a bed-of-nails fixture gives repeatable results or wears out fast. test-fixtures design-for-test manufacturing https://embeddedera.com/notes/usb-c-power-delivery-sink-for-non-phone-products/ https://embeddedera.com/notes/usb-c-power-delivery-sink-for-non-phone-products/ Tue, 15 Sep 2026 00:00:00 GMT How to add USB-C PD input to a product that needs more than 5 volts: controller choices, negotiation gotchas, and where a bare bit-banged sink breaks. firmware power-delivery usb-c https://embeddedera.com/notes/cyber-resilience-act-firmware-architecture/ https://embeddedera.com/notes/cyber-resilience-act-firmware-architecture/ Mon, 14 Sep 2026 00:00:00 GMT The EU's first CRA deadline landed this month. What it actually requires from firmware, and why retrofitting it later costs more than designing for it now. firmware compliance security https://embeddedera.com/notes/microcontroller-end-of-life/ https://embeddedera.com/notes/microcontroller-end-of-life/ Fri, 11 Sep 2026 00:00:00 GMT What an MCU EOL or NRND notice actually means, the four ways to respond, and how to qualify a replacement without a firmware rewrite going sideways. eol firmware obsolescence