A step-by-step guide to saving data to a microSD card using Zephyr RTOS v3.5 on the Nordic nRF52840 development kit. Covers the required Kconfig options (disk access, FAT filesystem, exFAT, SPI, GPIO), a devicetree overlay to configure SPI pins and CS line via the SparkFun Transflash breakout board, and the application code using the disk_access and fs APIs to mount the card, create a file, and write data to it. Useful for field-deployed embedded devices needing local data storage when internet connectivity is unreliable.
Table of contents
IntroductionQuick LinksHardwareEmbedded SoftwareKconfigDevicetree OverlayApplication SourceSummary1 Impression