Mayhem — The SD Card

The microSD card is not optional storage on a Mayhem device; it is where the firmware keeps almost everything that is not code. Capture files, decoder databases, frequency lists, per-app settings, logs, replay files and even the firmware images used for updates all live on the card, each in its own top-level folder. Understanding the layout is the difference between a device that “works” and one where half the apps silently fail because a folder or database is missing.

4.1 Format and capacity

The card should be formatted FAT32 or exFAT. Because the tooling and world map assume FAT32, the practical guidance is a card of 16 GB or smaller — capacity beyond 32 GB is not usable through the FAT32 path, so a large card gives no benefit and can cause problems. The reliable way to populate a fresh card is to extract a release’s ..._COPY_TO_SDCARD archive (the one that includes the ADS-B world map) to the root of the card; that single step creates every folder below and seeds the databases.

4.2 The folder layout

Every folder sits at the root of the card. The important ones:

Table 1 — Every folder sits at the root of the card. The important ones

Folder	Holds
FIRMWARE/	.bin firmware images used by the on-device Flash Utility
APPS/	external applications (.ppma / .ppmp) that appear in the menu
CAPTURES/	IQ recordings (.C16, .C8, .CU8) plus a .TXT metadata sidecar
FREQMAN/	frequency-manager database files, loaded by many apps
SETTINGS/	per-application settings (.ini files)
LOGS/	logs from ADS-B RX, ERT, TPMS, POCSAG and others
SUBGHZ/	.sub signal files for the FlipperTX app
SECPLUS/, KEELOQKEYS/, KEELOQREMOTES/	remote/rolling-code files and keys
PLAYLIST/	.PPL playlists for the Replay app
ADSB/, AIS/	decoder databases; the ADS-B world map lives in ADSB/
SSTV/, SPECTRUM/, BMP/	images for SSTV, Spectrum Painter and NOAA APT
WAV/, AUDIO/	Soundboard sources and recorded audio
SCREENSHOTS/, SPLASH/	screen grabs and custom boot splash images
LOOKINGGLASS/, WATERFALLS/, WHIPCALC/	presets for those utilities

Beyond these there are roughly two dozen more, one per app that reads or writes the card (BLERX, BLETX, CVSFILES, DEBUG, EPIRB, GPS, HOPPER, MACADDRESS, OOKFILES, REMOTES, SAMPLES and so on). The pattern is consistent: each app owns a folder named for it.

4.3 File formats worth knowing

• .C16 / .C8 / .CU8 — IQ captures. Raw complex samples written by the Capture app: .C16 is 16-bit signed I/Q, the others narrower. Each recording is paired with a .TXT metadata file recording the centre frequency, sample rate and related parameters, so the capture can be tuned correctly on replay or opened in host SDR software.
• .ppma / .ppmp — external apps. Standalone applications loaded from APPS/ at runtime rather than compiled into the firmware image.
• .sub — sub-GHz signals. The same format used by the Flipper ecosystem; FlipperTX replays these from SUBGHZ/.
• .ini — settings. Human-readable per-app configuration in SETTINGS/.
• .PPL — playlists. Ordered lists of files for the Replay app.
• .bin / .ppfw.tar — firmware. Update images placed in FIRMWARE/ for the Flash Utility; the .ppfw.tar bundle updates firmware and external apps together.

4.4 Data management and hygiene

• Keep the card in sync with the firmware. After a firmware update, missing or mismatched databases in ADSB/, AIS/ or FREQMAN/ are the usual cause of an app that launches but shows nothing. Re-extract the matching release’s SD archive when a release note calls for it.
• IQ captures grow quickly. A wideband recording is many megabytes per second of capture; CAPTURES/ is the folder to watch on a small card. The Wipe SD Card utility and the File Manager both help, but routine offload to a host machine (over SD Over USB or a card reader) is the sustainable approach.
• Treat captures and logs as data of record. IQ files and decoder logs can contain identifiable information from real transmissions in range. For any work beyond personal bench experiments, handle them accordingly and offload rather than leaving them on the device.

This completes the four-volume reference. Volume 1 covers what Mayhem is and its lineage, Volume 2 the capability set and the limits on transmitting, and Volume 3 installation and the update flow.