PocketMage SD Card Formatting Guide

WARNING
These steps will ERASE the SD card. Back up your data first.

This guide ensures SD cards are formatted in a way that is compatible with the PocketMage device.

Supported SD Card Requirements

  • Card size: 2 GB – 32 GB microSD
  • Filesystem: FAT32
  • Partition scheme: MBR (Master Boot Record)
  • Partitions: Single primary partition
  • Cluster (allocation unit) size: 32 KB
  • Sector size: 512 bytes (default)

X exFAT is NOT supported
X GPT partition tables are NOT supported
X 64 GB+ cards are NOT recommended unless you explicitly force FAT32 + MBR

Step 1 — Open diskpart

  1. Insert the SD card
  2. Open Command Prompt as Administrator
  3. Run:
    diskpart

Step 2 — Identify the SD card

list disk

Find the disk number that matches your SD card size.

Make sure you select the correct disk.

Step 3 — Format the card (MBR + FAT32)

select disk X
clean
convert mbr
create partition primary
format fs=fat32 unit=32k quick
assign
exit

Step 4 — Verify (optional)

  • Open Disk Management
  • Right-click the disk → Properties → Volumes
  • Partition style must say Master Boot Record (MBR)

macOS (Terminal — NOT Disk Utility)

macOS Disk Utility often creates GPT layouts that do not work.

Step 1 — Identify the SD card

diskutil list

Find the disk number (example: disk2).

Step 2 — Erase and create MBR + FAT32

diskutil eraseDisk FAT32 PM_SD MBRFormat /dev/disk2

Step 3 — Force 32 KB cluster size

sudo newfs_msdos -F 32 -c 64 /dev/disk2s1

Explanation:
-c 64 = 64 × 512-byte sectors = 32 KB clusters

Step 4 — Verify

diskutil info /dev/disk2 | grep “Partition Map”

Must say:
Partition Map Scheme: Master Boot Record

Linux

Step 1 — Identify the SD card

lsblk

Example device: /dev/sdb

Step 2 — Remove existing partition data

sudo wipefs -a /dev/sdb

Step 3 — Create MBR partition table

sudo parted /dev/sdb --script mklabel msdos
sudo parted /dev/sdb --script mkpart primary fat32 1MiB 100%

Step 4 — Format FAT32 with 32 KB clusters

sudo mkfs.fat -F 32 -s 64 /dev/sdb1

Step 5 — Verify

lsblk -o NAME,SIZE,PTTYPE

PTTYPE must be dos.

Final Checklist

Before using the card in PocketMage, confirm:

  • FAT32 filesystem
  • MBR partition table (not GPT)
  • One primary partition
  • 32 KB cluster size
  • Card size ≤32 GB

If any of these are incorrect, the card may not be detected.

If issues persist after following this guide, the SD card itself may be incompatible.

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