Context: Coldcard is is my opinion the most secure bitcoin hardware wallet currently available.
Coinkite states that an SD card with a FAT32 or FAT12 partition is required for use with the Coldcard
Under windows this is only possible when the card is 32Gb or less,
Here are the steps to use with a larger SD cards.
- Press start, Type "Disk Part..."
Delete all volumes by right clicking the volume on your SD card,
Create a volume of less than 32gb to be able to chose FAT32
You can now use this partition to put the .dfu file and update your firmware. https://coldcardwallet.com/docs/upgrade