The CM4 (Compute Module 4) is the fourth generation of the Raspberry Pi compute module. Unlike a standard Raspberry Pi (Model A or B), the CM4 is a System on Module (SoM) that lacks standard USB ports, HDMI ports, and SD card slots. Instead, it exposes the CPU, RAM, and eMMC via two high-density connectors (J1 and J2), designed to be plugged into a custom "Carrier Board."
While these sites often have "premium" tiers, they frequently offer older or common board schematics for free once you create a basic account. 4. Service Manuals cm4 94v0 schematics free
: An excellent guide on designing a custom CM4 PCB in KiCad is hosted on Instructables . The CM4 (Compute Module 4) is the fourth