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.
Budget temporary drawing surfaces from their actual dimensions, format, stride and overlapping lifetimes. A small changed rectangle on the display does not establish the size of the intermediate surface used to composite a transformed widget. The useful evidence is a scene-to-layer allocation map, followed by a peak-live-surface trace. Applicability: this article pins LVGL v9.3.0 with…
Prove fallback with three pieces of evidence: the operation is declined by the accelerated draw unit, a supported alternative actually executes it, and the resulting pixels satisfy the reference. An enabled software renderer alone proves none of those things. Keep unsupported-by-every-unit cases in the test plan so missing pixels cannot masquerade as successful completion. Applicability:…
Diagnose an alpha halo by tracking what RGB means at each stage. Straight RGB stores the unattenuated color; premultiplied RGB already includes multiplication by alpha. A consumer using the wrong interpretation can darken an edge twice or add too much color. Compare known pixels over at least two backgrounds before adjusting the artwork. Applicability: this…
Use the canvas buffer’s actual format and row stride for every CPU write. Width describes visible pixels; stride describes the byte distance between row starts. They are interchangeable only in a deliberately tightly packed layout. Packed index formats also need bit selection and palette handling, so a generic bytes-per-pixel loop is not sufficient. Applicability: this…
Define Back from the user’s navigation history, not from a menu page’s current object parent. In LVGL, pages move between display containers and internal storage as navigation changes. Reusing a page or hiding its entry does not automatically establish which previous destination remains valid. Applicability: this procedure pins LVGL v9.3.0 with a main-area menu and…
Map a selected table coordinate to a logical cell owner before looking up the application action. In LVGL v9.3.0, a visually merged span does not make every touch in that span report its leading column. Custom drawing adds another identity channel: the cell currently being drawn is not necessarily the cell selected by input. Applicability:…
Test an arc as three separate things: a numeric mapping, a rendered angle and a history-dependent pointer interaction. Unwrap the permitted sector across zero degrees before calculating its value range. Then test the invisible sector explicitly; a gap in the drawing is not automatically an exact, zero-tolerance prohibition on setpoint changes. Applicability: this guide pins…
A two-handle slider needs a numeric contract before it needs a visual treatment. Define low ≤ high, decide whether equality is valid, and identify which endpoint the current interaction owns. Test both user movement and programmatic pair updates: the widget’s endpoint clamping can make setter order significant. Applicability: this procedure uses LVGL v9.3.0 in LV_SLIDER_MODE_RANGE,…
Choose the integer unit first, then derive the spinbox range, displayed decimal position and editable digit steps from that same unit. A decimal point changes presentation; it does not convert the stored value. Verify sign crossings and rollover explicitly before treating the widget as an engineering setpoint editor. Applicability: this article is pinned to LVGL…
A hold-to-adjust control should have an explicit action session that can be canceled without waiting for an ordinary release. Admit repeat commands only while that session still owns the current view and input interaction. Treat press loss, input reset and navigation as cancellation paths, and ensure the eventual release cannot add a surprise final step….