Firmware requirements, peripheral integration, task coordination, fault diagnosis and verification for microcontroller products. Start from the actual hardware and acceptance conditions before choosing an implementation.
A latest-state input callback can miss a complete tap that begins and ends between reads. Preserve ordered press and release records, return one record per callback, and request another read while the permitted batch still has data. When the queue is empty, report the last admitted state rather than inventing a release. Applicability: this design…
Define an interactive shape explicitly, then reject points that are inside the object’s rectangular click area but outside that shape. A transparent corner or hole is a rendering property; it should not be assumed to make the corresponding input region transparent. Verify target selection separately from the pixels you draw. Applicability: the source boundary is…
A composite control needs one command owner even when several callbacks observe its click. Use the original event target to identify the source, the current target to identify the receiving object, and an explicit routing policy to decide who may issue the command. Bubbling distributes an event; it does not deduplicate application work. Applicability: this…
After mutating a shared lv_style_t, notify LVGL that the style changed. Changing the style’s stored property and repainting one widget are different operations. A correct update must reach every relevant consumer and refresh the layout or extended drawing information affected by the changed properties. Applicability: this article pins LVGL v9.3.0. The fixture attaches one shared…
Resolve an unexpected style one property, part, and current state at a time. First discard selectors that cannot match, then compare state precedence and equal-state ordering. Inspect local styles and active transitions separately. Reordering every style or adding another default-state override often hides the real conflict without changing the winning rule. Applicability: this procedure pins…
Check the limits stored in the existing littlefs superblock before reducing firmware’s name, file or attribute limits. An image can be incompatible with a smaller build even when every current filename and file happens to be short. The stored capability contract matters independently of today’s contents. This guide is pinned to littlefs v2.11.2. It qualifies…
Apply a default only when the setting’s documented policy permits it. A missing record, a malformed or integrity-failing record, and an explicitly cleared value carry different information. If firmware maps all three to the same fallback, it can silently undo an operator’s choice or conceal a storage fault. This article defines an original six-byte application…
Programming internal flash can block execution that still needs the affected flash bank. Moving one programming function to RAM is not enough if an interrupt vector, handler, helper function or constant remains in that bank. Qualify the complete access dependency path and the exact device’s concurrent-operation rules. The concrete example is a 2-Mbyte STM32F429 dual-bank…
Copying an existing filesystem image to a larger device preserves the image’s logical layout. Extra physical bytes become usable only when every intervening boundary permits them: driver addressing, region ownership, filesystem geometry, and application policy. Diagnose the first unchanged boundary before attempting a resize. The concrete filesystem example is littlefs v2.11.2 with unchanged logical block…
Gate the first storage read on the external flash’s actual exit-from-power-down sequence, not merely on the MCU’s wake event or the SPI controller becoming available. The device may still ignore ordinary commands while the software considers the system awake. The concrete example here is Microchip SST25PF040C, datasheet DS20005397E, with a separate Zephyr v4.2.0 SPI-NOR driver…