Once you have your PCB and schematic, perform these sanity tests:
Raspberry Pi Ltd. has released official "CM4 Carrier Board Schematics" (often called the "CM4IO" board). When you download these PDFs, here is what to look for: cm-4 94v-0 schematics
Common Mistake: Beginners often forget the "Disable eMMC Boot" jumper. The schematics show that pulling the eMMC_DISABLE_N pin (GPIO 40) low forces boot from an SD card. Once you have your PCB and schematic, perform
If you are designing from scratch, follow this workflow: Common Mistake: Beginners often forget the "Disable eMMC