The Raspberry Pi Compute Module 4 (CM4) takes everything that makes the Pi 4 great and repackages it into a compact, industrial-grade form factor designed for embedding into custom products. While the standard Raspberry Pi 4 is designed to sit on your desk with a display and keyboard, the CM4 is designed to disappear inside your device — whether that’s a CNC machine controller, a digital signage display, an industrial gateway, or a medical monitoring device.
The CM4 pairs a System-on-Module (SoM) with an interchangeable carrier board, giving designers complete flexibility to break out exactly the peripherals their project needs. It’s the bridge between the Pi ecosystem’s simplicity and the demanding requirements of embedded product development.
CM4 Overview and Variants
The CM4 is available in 32 variants — every combination of the following options:
RAM Options
- 1GB LPDDR4
- 2GB LPDDR4
- 4GB LPDDR4
- 8GB LPDDR4
Storage Options
- Lite (no eMMC): Uses a microSD card via the carrier board
- 8GB eMMC
- 16GB eMMC
- 32GB eMMC
Wireless Options
- With WiFi/Bluetooth: CM4 includes 2.4GHz/5GHz 802.11ac + BT 5.0
- Without wireless: For EMI-sensitive applications, industrial environments, or designs with their own wireless module
The naming follows: CM4[RAM][eMMC][W] — so CM4104000 means 4GB RAM, 0GB (Lite), no wireless. CM4108032 means 8GB RAM, 32GB eMMC, with wireless.
Key Hardware Features
The CM4 uses the same BCM2711 SoC as the Raspberry Pi 4, so software compatibility is identical. What changes is the physical interface and peripheral access.
Dual High-Density Connectors
The CM4 interfaces with carrier boards via two 100-pin high-density (Hirose DF40) connectors. These expose all of the BCM2711’s peripheral interfaces:
- PCIe Gen 2 x1 (this is the killer feature — not available on standard Pi 4)
- HDMI 0 and HDMI 1 (dual 4K@60fps output)
- 2x MIPI DSI display connectors
- 2x MIPI CSI camera connectors (4-lane)
- USB 2.0 (2x) — no USB 3.0 (see note below)
- Gigabit Ethernet PHY
- 28x GPIO, multiple UART/SPI/I2C interfaces
Important note: The CM4 does NOT have native USB 3.0. The Pi 4’s USB 3.0 ports come from a VIA Labs USB hub chip on the Pi 4 board, which is not included in the CM4 module itself. CM4 carrier boards can add their own USB 3.0 via PCIe.
PCIe: The Industrial Differentiator
The PCIe Gen 2 x1 interface exposed on the CM4 connectors is what makes it genuinely industrial-capable. Carrier boards can use this to add:
- NVMe SSD: 400–900 MB/s storage (vs 40 MB/s on SD card)
- USB 3.0/3.1: SuperSpeed USB for high-bandwidth peripherals
- SATA controller: 2.5″ or 3.5″ hard drive connectivity
- AI accelerator: Hailo NPU, Coral TPU, or custom inference chips
- Custom ASICs: Product-specific hardware via PCIe lanes
Carrier Boards: IO Board and Custom Designs
The CM4 is nothing without a carrier board — the module provides the compute, the carrier provides the I/O that specific applications need.
Official CM4 IO Board
The official Raspberry Pi CM4 IO Board is the reference carrier for development. It provides:
- Full-size HDMI connectors (2x)
- Gigabit Ethernet
- 2x USB 2.0 Type-A
- PCIe x1 slot (M.2 with adapter)
- MicroSD slot (for Lite modules)
- 40-pin GPIO header (Pi-compatible)
- Camera/display flat cable connectors
- USB-C power input
Third-Party Carrier Boards
The CM4’s ecosystem includes dozens of carrier boards for specific applications:
- Waveshare CM4 boards: Various form factors — mini-ITX, PoE, router, NAS, and industrial variants
- DFRobot Beetle CM4: Ultra-compact carrier for embedded products
- Router-format carriers: mPCIe slots for LTE modems, dual Ethernet for router/gateway projects
- Industrial carriers: DIN rail mounting, -40°C to 85°C operating range, RS-485, CAN bus
Custom Carrier Board Design
For volume production, designing a custom carrier board is the ultimate CM4 integration. Raspberry Pi provides the CM4 Datasheet and schematics under open hardware license. The BCM2711 peripheral design is well-documented, and community KiCad/Eagle templates exist for the Hirose DF40 connectors.
A minimal custom carrier needs only: power regulation (5V input → 3.3V + 1.8V for module), the two DF40 connectors, and the peripherals your product uses. This lets you build a production PCB with exactly what you need and nothing you don’t.
eMMC vs SD Storage and NVMe
Storage choice has major implications for CM4 performance and reliability in embedded applications.
eMMC (Recommended for Production)
eMMC (embedded MultiMediaCard) is soldered directly to the CM4 module:
- Reliability: Far more reliable than consumer SD cards. eMMC uses wear levelling, error correction, and industrial-grade NAND flash.
- Speed: eMMC 5.1 delivers 200–300 MB/s read, 100–200 MB/s write — 5-8x faster than SD.
- Vibration resistance: Soldered flash vs socketed SD eliminates connector failure under vibration (critical for vehicles, industrial equipment).
- Write endurance: eMMC typically rated 3,000–10,000 P/E cycles vs 1,000–3,000 for cheap SD cards.
Lite + MicroSD (Development/Low-Budget)
The Lite variant uses a standard microSD via the carrier board. Fine for development and light-duty applications, but:
- SD cards fail much more often in 24/7 embedded deployments
- Not suitable for high write-frequency applications (logging, databases)
- Use high-endurance industrial SD cards (e.g., Western Digital Purple, Kingston Industrial) if you must
Lite + NVMe SSD (Best Performance)
CM4 Lite modules on carrier boards with M.2 slots can boot from NVMe SSD via PCIe:
- 900+ MB/s sequential read — near PC-class storage performance
- Much higher write endurance than eMMC
- Larger capacity (128GB, 256GB, 1TB) without cost premium
- Ideal for applications requiring large databases, video recording, or fast data processing
Flashing and Programming the CM4
Flashing a CM4 with eMMC is different from Pi — you can’t just put an SD card in.
Using rpiboot
The CM4 eMMC appears as a USB mass storage device when the module is in flash mode. To flash it:
- Install
rpibooton your computer (available for Windows, macOS, Linux) - On the CM4 IO Board, install a jumper on J2 pins 1-2 (nRPIBOOT bridge)
- Connect the USB-C port to your computer
- Run
sudo rpiboot— the eMMC appears as a USB drive - Use Raspberry Pi Imager to write your OS image to the eMMC device
- Remove the jumper, reboot — the CM4 boots from eMMC
Production Flashing at Scale
For manufacturing 10, 100, or 1000+ units, Raspberry Pi provides the usbboot tool for automated flashing. Combined with a custom provisioning image that includes your application and configuration, you can flash a complete device in 2–3 minutes per unit.
Real-World Industrial Use Cases
The CM4 is in active production use across many industries. Here are common applications:
Digital Signage
The CM4 is arguably the most popular platform for commercial digital signage displays. Dual 4K HDMI output, reliable eMMC storage, custom carrier board with power over Ethernet — and a low enough BOM cost for large deployments. Companies like Screenly and Yodeck ship CM4-based players.
Industrial IoT Gateways
CM4 carrier boards with RS-485, Modbus RTU, CAN bus, and multiple Ethernet interfaces serve as Modbus-to-MQTT gateways, SCADA edge nodes, and Industrial IoT concentrators in factories and utilities. Running Node-RED or custom Python on Linux is far more capable than traditional PLCs for complex logic.
Thin Client / Kiosk
Point-of-sale terminals, kiosk displays, and customer-facing interactive screens use CM4 for its small footprint, quiet (fanless) operation, and manageable cost at volume.
3D Printer / CNC Controllers
Klipper (3D printer firmware) can run on CM4 for high-performance motion control. Custom CM4 carrier boards designed for 3D printing (like the Mellow Fly boards) integrate stepper drivers directly on the carrier, creating a tight printer controller board running full Linux.
Network Appliances
CM4 carrier boards with dual Gigabit Ethernet and optional LTE modem (via PCIe mPCIe) create capable router/firewall appliances running OpenWrt, pfSense (unofficially), or custom iptables configurations. The PCIe interface enables hardware switching chips for line-rate forwarding.
CM4 vs Raspberry Pi 5: Which Should You Choose?
| Factor | CM4 | Raspberry Pi 5 |
|---|---|---|
| CPU Performance | BCM2711 Cortex-A72 @ 1.5GHz | BCM2712 Cortex-A76 @ 2.4GHz (2.5x faster) |
| Form Factor | SoM — embeds in custom products | Standard PCB — standalone use |
| eMMC Storage | Available (8/16/32GB) | Not available (MicroSD or NVMe) |
| Carrier Board Flexibility | Full custom carrier possible | HAT ecosystem only |
| Ease of Setup | Complex (requires carrier board) | Simple — plug and play |
| Prototyping Speed | Slow (carrier design + PCB fab) | Fast — immediate use |
| Production Volume | Designed for volume production | Not designed for embedding |
Choose CM4 if: You’re building a product for volume manufacturing, need eMMC storage, require a custom carrier board, or need the compact SoM form factor.
Choose Pi 5 if: You’re prototyping, building a one-off project, need maximum performance, or want plug-and-play simplicity.
Frequently Asked Questions
Is Raspberry Pi CM4 still the current Compute Module?
As of 2024, CM4 is the current shipping Compute Module based on BCM2711 (Pi 4-class). A CM5 based on the Pi 5’s BCM2712 is expected but has not been officially released at time of writing. CM4 remains excellent for production deployments and is widely available from Raspberry Pi’s distributor network.
How do I get the CM4 if it’s out of stock?
CM4 stock has been challenging since 2021. Register for stock notifications with authorised distributors like Zbotic.in. The Lite variants (no eMMC) and less popular RAM configurations often have better availability. For critical production timelines, consider ordering 3–6 months ahead of your production schedule.
Can I replace a Raspberry Pi 4 with a CM4 in my existing project?
If your project uses the standard Pi 4 HAT connector and a display, you can use a CM4 on the official IO board as a drop-in replacement for testing. For production, you’d design a custom carrier. Software is fully compatible between Pi 4 and CM4 — the same Raspberry Pi OS image boots on both.
What operating temperature does the CM4 support?
The standard CM4 is rated 0°C to 85°C operating temperature. This is suitable for most industrial enclosures. For extreme environments (outdoor deployments, automotive, cold storage), industrial-grade CM4 variants are available from specialist distributors, rated to -40°C to +85°C with conformal coating for moisture resistance.
How do I update CM4 firmware in a deployed product?
Over-the-air (OTA) updates are critical for deployed embedded products. The recommended approach is to use a dual-partition setup (A/B partitioning) so you can flash the inactive partition and flip a bootloader flag to switch to it — if the new image fails, the system rolls back automatically. Tools like RAUC, Mender, or custom scripts on top of rpiboot’s network boot capability handle this professionally.
Start your embedded project today. Explore Raspberry Pi boards and compute modules at Zbotic.in. From CM4 to Pi 5, Pi Pico, and accessories — everything you need for industrial and embedded projects, with fast delivery across India.
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