A freshly flashed signage card that shows one small boot drive of about 250 MB on an 8 GB card is not a failed write. Windows cannot read the Linux data partition that holds the rest of the card, so it shows no second drive and offers to format. When the screen still shows nothing, check the image's minimum hardware requirement first.
You flash a signage image to an 8 GB microSD card, slide it back into the PC to check, and Windows shows one drive called boot with 252 MB total and 205 MB free, then offers to format the disk. The gigabytes are not missing and the write has not failed. The image splits the card into a small boot partition plus a data partition on a Linux filesystem Windows cannot read, so the rest of the card sits there without a drive letter. That is the normal look of a correctly written card.
When the screen still shows nothing, the cause is usually a mismatch between the image and the board: the build written here, a kiosk player image at version 0.0.15, needs a newer board generation than the one it went into. This page explains the two partitions, what Windows is really telling you, and the check that finds the actual fault.
What the two partitions are
The imaging utility does not copy files onto a formatted card. It writes a picture of a whole disk, partition table included, sector by sector, and the picture in a player image carries two partitions.
The first is a small FAT boot partition at the size Windows reported, holding the start-up files: the loader and firmware the board reads before anything reaches the screen. The second takes the rest of the card and carries the player system itself, on a Linux filesystem, ext4 in this image.
The split is deliberate. The board's start-up code is built to read FAT, and the player software runs on Linux and lives on the filesystem Linux uses. One card, two partitions, each doing one job.
What Windows shows and why
Windows mounts the FAT partition and gives it a letter: D:, with 205 MB free on the first look after the write. The ext4 partition gets no letter. Windows carries no driver for ext4, so Disk Management lists the partition but cannot mount it or show its contents, and Explorer omits it from the drive list entirely.
That unidentified partition is what triggers the format offer. Decline it. Accepting erases both partitions and leaves the board nothing to load.
The card looked different before the write: one plain drive of about 7.8 GB, a volume Windows could read, because a formatted blank card is a single volume. After the write that volume is gone, replaced by the image's two. The imaging utility still reports the device at 7.7 GB on every attempt, because it reads the raw device, partitions and all. The card has not shrunk; only the visible letter has.
Why the screen stays blank
With the write off the suspect list, a blank screen points at the board. That is what happened with the build in question: the card went into a board several generations older than the minimum the image lists. The board never started the image, and the screen reported no signal. A second image from a different maker gave the same silence on the same board, which is the giveaway that the fault sits with the hardware pairing, not the card.
Every player image is built for one board or one board generation, and the page you download it from lists the minimum hardware it supports. Read that list before writing the card. An image built for a newer generation will not start on an older board, and no number of re-flashes changes that; use an image built for the board you have.
Sort the symptoms this way:
- The screen reports no signal and shows nothing at all: the board is not starting the image. Check the board model against the image's minimum hardware list first.
- A splash screen appears and nothing after it: the board boots but the player never takes over. Showing only a splash screen on an embedded Linux kiosk boot covers that stage.
- The show starts but the screen goes black on the videos: a playback fault, not a boot fault. A black screen on video is the article for it.
A blank boot medium announces itself differently on some machines. An HMI panel given an empty CF card at least says so, booting to a no-user-program message on a blank CF card; a small player board that fails its boot simply stays dark.
Example: reading an 8 GB card that shows one small boot drive
The inputs, each with its source:
- Card as sold: 8 GB microSD, the card itself.
- Drive after the write: D:, total as Windows reported it, 205 MB free, from the drive properties.
- Device size: 7.7 GB, as the imaging utility reported it, before and after the write.
- Build written: kiosk player image version 0.0.15.
The rule in words: a player image fills the whole device, a boot partition whose size the image fixes, about 250 MB on this build, plus a data partition over the remainder on a filesystem Windows cannot mount. A healthy write therefore shows exactly one small drive, with the balance of the card present but invisible.
The arithmetic:
- Boot files in use: the drive's reported total minus the 205 MB free, which is 47 MB. That is loader plus firmware, a few tens of megabytes, as this stage should be.
- Data partition: 7700 MB minus the 252 MB boot drive leaves 7448 MB. The absent second drive holds about 7448 MB of player system.
- Sum check: the 252 MB drive plus the 7448 MB data partition is 7700 MB, exactly the device size the imaging utility reports. Every megabyte of the card is accounted for.
The result: the write succeeded. The format offer is Windows reacting to a partition type it cannot read; the absent drive letter is a missing driver in Windows, not missing data on the card.
The decision it leads to: for this build, a boot drive near 250 MB with tens of MB in use, plus a device size of 7.7 GB in the imaging utility, means the card is good, so stop re-flashing and turn to the board. A boot drive showing 0 MB, or no drive at all after a completed write, is a genuine failure: write again and run the utility's verify pass before the card goes anywhere near the board.
How to verify the card
- Let the write finish, then run the verify pass most imaging utilities offer. It re-reads the card and compares it against the image, which settles the question the drive list cannot.
- Re-insert the card and look for one small drive called boot, with about 47 MB of start-up files in use and roughly 205 MB free.
- Decline any format prompt.
- Open Disk Management and confirm the card carries two partitions: the small FAT one, healthy, and one Windows cannot mount. That is the expected picture.
- If the card comes up read-only or fails to refresh after a write, run a RESCAN in DiskPart; if the object stays stuck, exit DiskPart and restart it, or restart the PC. Those steps come from the imaging utility's own troubleshooting documentation, so check yours for the exact wording.
- Then check the pairing: the image's download page lists the minimum hardware it supports, and the board must meet it.
What to do
If the sign you want is a promotion or notice loop, not a kiosk you assemble from parts, skip imaging altogether. The panel-mount player range plays images and MP4 straight from a microSD card or USB stick with no subscription, and keeps a copy in internal memory, so the show carries on when the card comes out. For the smallest screens, playing video from an SD card on a small SPI TFT covers the storage side of a bare module. And if the build is heading for the shop floor as a status board, where a small screen fits on an andon board is worth a read before you pick the screen.
Recommendation: Treat one boot drive of about 250 MB on a freshly flashed 8 GB card as success: decline the format prompt, leave the card alone, and move to the board. Before writing any player card, read the image's documentation for the minimum board revision it supports and match the image to the hardware you have; an image built for a newer generation will not start on an older board, however many times you re-flash. Reserve a re-flash for a boot drive that shows 0 MB, or no drive at all, after a completed write.
Questions
Why does an 8 GB card show only about 7.7 GB?
An 8 GB card holds 8,000,000,000 bytes, because card makers count in decimal. Windows displays binary gigabytes of 1,073,741,824 bytes, and 8,000,000,000 divided by 1,073,741,824 is about 7.45. So roughly 7.45 GB shown for an 8 GB card is the card's real size. Imaging utilities count and round in their own units; one flashing session reported 7.7 GB on the same card, and that too is a healthy card.
Should I format the card when Windows asks?
No. Windows asks because the card now holds a partition type it cannot identify, and accepting the prompt erases both partitions, leaving the board nothing to load. To start over, write the image again with the same imaging utility; it re-creates the boot and data partitions in one pass. Format the card only when you want it empty for ordinary storage again.
Does the boot drive stay small on a bigger card?
Yes. The image fixes the boot partition's size, so it stays about 250 MB whether the card is 8 GB or 64 GB, and the data partition takes the rest. A larger card shows the same small drive, a bigger unrecognised remainder, and the same format prompt. Card size changes nothing about whether the write succeeded; the boot drive's used space and the utility's device size do.
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