A standard PCIe connector allows for expansion cards (like NVMe SSDs, AI accelerators, or extra network interfaces). 6. GPIO Header
The open-source KiCad EDA (Electronic Design Automation) suite is the go-to tool for creating new CM4 carrier boards. The Raspberry Pi Foundation itself released the official CM4IO board's schematic ( .kicad_sch ) and PCB layout ( .kicad_pcb ) files in KiCad format. This has inspired a massive ecosystem of community-led CM4 projects on platforms like GitHub. You can find numerous KiCad projects for minimal carrier boards, PCIe expansion boards, and specialized IoT carriers, ready for you to learn from or use as a starting point for your own design. cm4 94v0 boardview new