🛠 Premier démarrage d'un Compute Module 3 sur la carte CMIO3

Objectives

Understand that a Compute Module 3 (CM3) is a bare module: without a carrier board, it has no power connector, HDMI, Ethernet, or Wi-Fi. This tutorial assembles the official kit (CM3 or CM3 Lite module + Compute Module IO Board V3, also known as CMIO3) and performs the first boot of Raspberry Pi OS.

Hardware

• A CM3 module (4 GB eMMC) or CM3 Lite (no storage, boots from SD card via the SDX interface exposed on the SODIMM connector)
• Compute Module IO Board V3 (CMIO3) carrier board or compatible
• microSD card (8 GB min.) for the system image
• 5 V / 2.5 A power supply via micro-USB, HDMI cable, USB keyboard
• A PC to prepare the card with the 32-bit Raspberry Pi OS image (Raspberry Pi 3 images work on CM3, BCM2837 quad Cortex-A53 at 1.2 GHz, 1 GB LPDDR2)

Complete code

# Sur le PC : écrire l'image Raspberry Pi OS (32 bits, branche Pi 3) sur la microSD
unzip -p 2024-xx-xx-raspios-bookworm-armhf-img32.zip | sudo dd bs=4M of=/dev/sdX status=progress conv=fsync
# (ou utiliser Raspberry Pi Imager, cible : Raspberry Pi 3)

# Insérer la microSD dans la CMIO3, insérer le module dans le connecteur SODIMM
# (à 30°, contacts dorés vers la carte porteuse, pousser puis enfoncer), alimenter.

# Sur le CM3 démarré : vérifier l'identité du système
lsb_release -a
vcgencmd versionmap

Expected verification

The green LED on the CMIO3 blinks during boot and then stays on; the desktop (or the command prompt in the Lite version) appears on HDMI. lsb_release -a displays Raspberry Pi OS and vcgencmd versionmap responds, proving that the BCM2837 firmware is running. The CMIO3's Ethernet (USB chip) provides network access via DHCP.

Common errors

• A CM3 (with eMMC) inserted with a valid microSD card still boots from its empty eMMC: the BCM2837 has no EEPROM or configurable BOOT_ORDER, so eMMC takes precedence. See the tutorial "flasher-emmc-cm3-rpiboot".
• Forgetting that the module has no Wi-Fi or Bluetooth: network connectivity comes solely from the carrier board.
• Insufficient power supply: the CM3 requires up to 3.5 W on VBAT; a low-quality smartphone charger causes voltage drops.
• Module not fully inserted into the SODIMM: no display, LED off — the connector is fragile, never force it flat.