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.
When only one MCU has advanced, the product must enter a deliberately supported intermediate state or a defined restricted state. Do not let “both images downloaded” stand in for a coordinated update. Specify which version pairs can communicate, which functions remain available, and how the next transition proceeds after either processor resets. This article proposes…
Choose an MCUboot swap mode from flash geometry, usable image capacity, per-region erase cost, and interrupted-update recovery. A small scratch partition can save address space while concentrating erase cycles. Removing scratch does not remove flash wear; offset and move modes distribute work differently and impose their own layout requirements. This comparison is pinned to the…
Resolve touch conflicts by specifying which object may perform each application action, then replay complete press, movement, and release sequences while tracing events and scroll offsets. A finger moving over a button inside a scrollable list is one input stream. Treating every callback as an independent command can turn an attempted scroll into an unintended…
A screenshot test is useful only when the same application state produces the same pixels. Freeze the rendering inputs, advance simulated time deliberately, and separate ordinary comparison from reference-image approval. Otherwise a changed font package, a different animation phase, or an accidentally missing baseline can look like a product change. Applicability: this procedure targets desktop…
Create one timeout state and one remaining-ticks value for the logical operation, then update that pair before each additional wait. Do not restart the original timeout merely because some bytes, replies or resources became available. Partial progress can justify continuing the operation without granting it a new time budget. This guide pins FreeRTOS Kernel V11.1.0…
An interrupt can enter promptly yet encounter deferred floating-point context-saving work later, at its first FPU instruction. Measuring only the first GPIO transition inside the handler can miss that cost. Qualify the complete deadline-critical path under both floating-point-active and inactive interrupted contexts. This guide concerns Cortex-M4 processors with the optional FPU, commonly called Cortex-M4F, using…
A queue set works reliably when selecting a member and consuming one item from that member are treated as a single application-level obligation. Do not let a diagnostic task, a secondary worker or a recovery shortcut read a member independently. Otherwise, the set can retain a readiness event after the corresponding payload has disappeared. This…
Keep the month being browsed, the date being edited and the committed device value in separate application fields. An LVGL calendar displays and reports dates; browsing a month or marking “today” must not itself change the device clock. Validate a complete year-month-day snapshot, then submit it only through an explicit Apply action. Applicability: LVGL v9.3.0…
Choose an observer registration API according to the target’s lifetime, then give every subscription exactly one cleanup path. Widget-associated observers can be removed automatically when that widget is deleted. A generic target pointer has no such lifecycle hook, even when the pointer happens to contain a widget address. Applicability: LVGL v9.3.0 with LV_USE_OBSERVER enabled, one…
A draw callback should describe pixels from already-prepared state. It must not change widget properties, create or delete widgets, or request another invalidation while rendering is in progress. Being on the correct UI thread does not make those operations legal during the drawing phase. Applicability: LVGL v9.3.0, a serialized UI owner, the ordinary software draw…