STM32WL Companion help packing, 23 October 2026

Small STM32WL USB Companions now use the existing packed help producer with a 256-byte history. Every command, option and terminal suffix is retained. The same feature-gated CompanionHelp.inc supplies the packed and ordinary output. nRF52 RAK Full keeps its 2,048-byte history; ESP32 retains its ordinary help printing path. Contact/channel limits and the application/filesystem boundary are unchanged.

Only the selected CompanionHelpPacked.cpp is compiled as C++17. A source-role policy registers that override for STM32WL Companion builds, excludes other roles and reuses the existing per-object helper without installing nRF52 trims. Other project sources and framework/library language standards remain unchanged. The final producer also requires the STM32WL platform and text terminal capability.

Native tests compare the STM32 output with the preceding ordinary-printing bytes, including both USB and network terminal suffixes. They exercise short, zero and invalid writes, overlapping matches, ring wrap, malformed tokens and a match farther back than the selected history. The STM32 profile's USB help remains 1,908 bytes including its terminal suffix. Its SHA-256 is 9e587ac9f287c8f8fe64fe5c899fe635b6de5d6cf436c4c43a27ffd4add42474. C++11 callers link and execute the actual C++17 producer under address and undefined-behavior sanitizers for both STM32WL and RAK Full.

The standalone Cortex-M4 object comparison saves 733 bytes including the decoder and its data, before whole-firmware LTO effects. Emitted producer and helper frames total 384 bytes; a 512-byte caller/output reserve keeps that local estimate at 896 bytes within the existing 1,024-byte minimum stack allowance. This is compiler frame accounting, excluding physical interrupt high-water. The complete firmware's linked size is a separate build check.

Complete builds at 5b20bf37 passed sequentially with the Cascade profile and unchanged flash boundaries. All four USB Companions also passed the canonical OTA packaging and runtime RAM checks:

Target	Linked flash used / limit	Flash remaining
RAK 3x72 USB Companion	228,920 / 229,376 bytes	456 bytes
Wio E5 Mini USB Companion	228,736 / 229,376 bytes	640 bytes
Wio E5 USB Companion	228,716 / 229,376 bytes	660 bytes
Tiny Relay USB Companion	228,784 / 229,376 bytes	592 bytes

The Wio E5 Mini repeater also passed its cable-only build and runtime RAM checks at 245,356 / 245,760 flash bytes, leaving 404 bytes. These integrated STM32WL targets expose no supported saved radio-switch tuning features; the unavailable machinery is omitted without changing their radio commands or stored profiles. These are build checks, not physical device qualification.