Storage & SD¶

Apps live in the Cyber Fidget's internal storage, the companion page is built into its firmware, and app art is compiled into each app when it is built. The microSD card holds music, voice recordings, the companion's speech-recognition payload, and any optional companion page override; it does not hold apps or supply their art.

Draft section

THIS SECTION IS STILL IN DRAFT

Inserting and removing cards safely¶

Use the battery switch - software power-off is not enough

Slide the battery switch OFF before inserting or removing a microSD card. Powering the device off from the power app does not fully de-energize the card slot: on current firmware, some of the slot's signal lines can stay electrically active while the device appears off. A card inserted against active signal lines can be permanently damaged - current flows into the unpowered card through its protection diodes, which can corrupt the card's controller so badly that no computer will recognize it afterward.

The battery switch cuts power to everything, so with it OFF a card swap is always safe.

In short:

Safe: battery switch OFF, then insert or remove the card.
Not safe: swapping cards while the device is on - including on a "No SD card" screen - or after powering off through the power app.
Make sure the card is fully seated (it should sit flush in the slot). A partially inserted card can make contact on its signal pins without receiving power, which risks the same damage.

A firmware update that removes this hazard is in development; the battery-switch habit remains good practice even after it ships.

Recommended card specs¶

Spec	Recommendation
Format	FAT32 (required)
Size	1 GB – 32 GB (FAT32 max). Larger cards may need manual formatting to FAT32.
Speed	Class 4 or higher. Class 10 / UHS-I recommended for faster read/write.
Form factor	microSD (not full-size SD)

Tested brands

Phison-based cards in the 4–32 GB range work well. Avoid ultra-cheap no-name cards — they can have compatibility issues with SPI-mode access.

Formatting¶

Format your card as FAT32 before first use:

Windows: Right-click the drive → Format → FAT32. For cards > 32 GB, use a tool like Rufus or SD Card Formatter.
macOS: Disk Utility → Erase → MS-DOS (FAT).
Linux: mkfs.vfat /dev/sdX1

Use cases¶

Music - The card holds music files
Voice recordings - The card holds recordings made with Voice Notes
Phone companion - The card holds its speech-recognition payload and may hold a newer page override; the device already has the companion page in its firmware
File browsing - The WiFi web portal can list, upload, and download the card's files, which is the easiest way to move music and recordings on and off

Hardware details¶

The SD card connects to the ESP32 via SPI:

Pin	Signal
GPIO 5	SCK (clock)
GPIO 19	MOSI (data out)
GPIO 21	MISO (data in)
GPIO 8	CS (chip select)

The SD card shares the 3.3V_RGB power rail (GPIO 2 enable), so it is powered down when the AUX regulator is disabled in deep sleep. The SPI bus lines, however, live on the always-on 3.3V domain, and on current firmware they can remain driven during deep sleep (the ESP32's GPIO deep-sleep hold latches digital pads at their pre-sleep state) - which is why swapping cards requires the battery switch, not just software power-off. See Inserting and removing cards safely.