MCU & RTOS Firmware

Measure raw-flash amplification with separate ledgers for useful application payload, filesystem program requests, and erase operations by block. A single “bytes written” counter cannot explain whether a settings workload creates extra programming, repeatedly erases a small region, or merely repeats unchanged application requests. This method uses littlefs v2.11.2 callbacks as one observation boundary. It targets…

A flash ring log needs an explicit erase-eligibility rule before it wraps: a sector may be reclaimed only when every record it contains is eligible for removal. If an incident pins even one record in that sector, ordinary rotation must stop or use a separately qualified retention path. Finite storage cannot guarantee unlimited recording and…

Recover an append-only log by accepting a contiguous prefix of fully validated records and stopping at the first incomplete or invalid frame. Return both the accepted records and the exact stop offset. Do not search for the next familiar marker and silently join data across an unexplained gap. This article defines an original, synthetic framing…

Deleting an NVS ID removes its current logical value; it does not guarantee that every previous payload byte has been erased. A factory-reset claim must say whether it means resetting application behavior, clearing a particular storage region, or meeting a separately defined sanitization requirement. Those outcomes require different evidence. This article examines direct Zephyr v4.2.0…

Before calling a failed flash write “filesystem corruption,” capture the exact request at each layer: device, offset, length, buffer, return code, and whether any physical command was issued. A driver rejecting an invalid request is a different event from a chip accepting a command and storing unexpected bytes. This diagnostic method uses the Zephyr v4.2.0…

Treat each persistent NVS record ID as an assigned product interface. Once shipped, its meaning must remain stable or be retired explicitly. Reusing an old ID for a different setting can make intact, readable bytes become the wrong instruction to new firmware. This article targets direct use of Zephyr v4.2.0 NVS and the application’s record-ID…

Choose a counter checkpoint policy from an explicit loss budget, then verify the resulting storage workload. “Save less often” is incomplete until you state how many accepted events may disappear after a sudden reset, how commit failures are handled, and whether the recovered total may move backward. This article concerns a cumulative event count whose…

nvs_read_hist() selects an older stored entry for one NVS ID. It does not reserve that entry against reclaim, identify an application generation, or promise a fixed number of backups. Use it for qualified historical inspection, and make missing or unsuitable history an explicit application outcome. This article targets Zephyr v4.2.0 and a single NVS region….

Size an NVS region for the live record set, record overhead, and the space needed to copy live records during reclaim. Raw partition bytes are not all available to application values. A configuration that stores every setting once can still fail after repeated replacements because its steady-state reclaim path has no useful headroom. This worksheet…

A failed mount tells you that the current software did not establish a usable filesystem. It does not tell you that the storage is empty or that its contents may be discarded. Stop automatic reinitialization, preserve evidence, and classify the failure before choosing recovery or an explicitly authorized format. This procedure uses littlefs v2.11.2 as…