You can prototype a handheld gaming console with a Raspberry Pi Compute Module 4 (CM4), but the module is not a complete, plug-in handheld computer: it needs a carrier board to connect power, display, USB and controls. Start with a CM4 on a development carrier, test the display and input hardware on the bench, then design the battery system and enclosure around parts that work together.
What a CM4 handheld needs
The CM4 is a system-on-module built around Raspberry Pi 4 core components, with optional eMMC flash storage. It connects to other hardware through two 100-pin high-density connectors; a carrier board exposes the interfaces a handheld needs. Raspberry Pi’s CM4 documentation lists 1GB, 2GB, 4GB or 8GB of RAM, and Lite (no onboard eMMC) or 8GB, 16GB, 32GB or 64GB eMMC variants. Wireless availability also varies by SKU, so check the exact module before planning networking or software setup.
Plan for six integrated subsystems:
- Compute and carrier: the CM4 and a development or custom board to connect it to the rest of the console.
- Display: an HDMI or MIPI DSI panel, cable or adapter, mounting and any required display configuration.
- Battery and charging: a protected battery, charger, voltage conversion and a way to shut down safely.
- Controls: buttons, a D-pad and, if needed, analog sticks, plus the GPIO or microcontroller electronics to read them.
- Audio: an amplifier and speakers, with a headphone connection if desired.
- Cooling and enclosure: thermal hardware, controls and screen mounts, and room for wiring and service access.
Choose the carrier before designing the case
A CM4 IO Board is useful for early bring-up because it provides accessible connections, including two HDMI ports, two MIPI DSI connectors, two USB 2.0 ports, GPIO, Gigabit Ethernet, PCIe and a fan connector. It accepts power through 5V GPIO or a 12V barrel jack. It is a development board, not a compact handheld carrier: its size and connector layout make it more suitable for testing than for a finished pocketable enclosure.
Once the module boots and the peripherals work, a smaller custom carrier can reduce size and place connectors where the enclosure needs them. The trade-off is that a custom board takes more design and debugging effort, and it is less convenient to rework than a development board.
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- Upgraded processor BCM2711, quad-core Cortex-A72 (ARM v8) 64-bit SoC, more powerful performance
- Faster eMMC Flash storage, up to 100 MBytes/s data rate, which is four times faster than the CM3+
- Adopts B to B connectors, more stable than the Goldfinger edge connector of previous generations
- Onboard new Gigabit Ethernet PHY supporting IEEE1588, suitable for network applications
- Onboard new PCIe Gen 2 x1 interface, allows connecting more useful modules
| Carrier choice | Useful for | Trade-off |
|---|---|---|
| CM4 IO Board | Initial boot, networking, display and peripheral tests; broad access to interfaces. | Bulky for a handheld enclosure and includes connections a finished console may not need. |
| Custom compact carrier | A smaller final layout tailored to the screen, battery, controls and enclosure. | Requires board design and validation; debugging and hardware changes can be harder. |
Select a display and verify its connection
For a handheld with physical controls, a 5–7-inch display is a practical starting range, not a universal requirement. Compare resolution, refresh rate, brightness, viewing angles, power draw, connector, driver support and whether touch is needed. Confirm the panel’s cable pinout and voltage before ordering; a connector that physically fits is not proof that its wiring is compatible.
| Display connection | Prototype considerations | Integration trade-off |
|---|---|---|
| HDMI | Often the simpler way to bring up a screen early. | Usually takes more board space and power than a directly connected DSI panel. |
| MIPI DSI | Needs a compatible panel, correct cable or adapter, and supported configuration. | Can be a more integrated fit, but wiring and display support need careful verification. |
Raspberry Pi’s CM4 IO Board instructions describe connecting a compatible display to DISP0/DSI0 or DISP1/DSI1 using a 22-pin-to-15-pin adapter. For the documented 7-inch display overlay, add dtoverlay=vc4-kms-dsi-7inch to the configuration and reboot. Confirm that the chosen panel and software setup match those instructions rather than assuming every DSI screen uses the same overlay.
Plan storage and software around the CM4 SKU
Choose the module and boot medium together. A Lite CM4 has no onboard eMMC and therefore needs separate storage for the operating system and games. An eMMC model has onboard storage; select a capacity that fits the system and intended library, and account for how you will install or update its software. The module’s RAM and wireless options also differ by SKU, so settle those choices before buying rather than treating “CM4” as one fixed configuration.
Rank #2
- 8GB RAM; 32GB eMMC Flash with WIFI
- Upgraded processor BCM2711, quad-core Cortex-A72 (ARM v8) 64-bit SoC, more powerful performance
- More options for RAM (1GB/2GB/4GB/8GB), competent for large-scale data compilation
- Faster eMMC Flash storage, up to 100 MBytes/s data rate, which is four times faster than the CM3+
- Option for fully certified radio module, the same one used on Pi4B, supports either PCB trace antenna or external antenna, more suitable for industrial applications
Raspberry Pi Magazine describes installing RetroPie and enabling its Samba share so files can be copied over the network to ~/RetroPie/roms. The exact installation steps can change as RetroPie, Raspberry Pi OS images and emulator packages are updated, so follow the current project documentation for the software release you use. Only use game files you are legally entitled to use; having a console emulator does not grant rights to copyrighted game files.
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Do not choose a battery solely by its advertised capacity. Cell chemistry and cell count determine the compatible charger, protection circuitry and voltage-conversion stages. Work out the power tree before fixing the enclosure dimensions, and include a controlled shutdown path so the system can stop cleanly when charge is low rather than abruptly losing power.
- Account for the CM4 under load, display backlight, audio amplifier, fan and any USB devices when estimating consumption.
- Use charging and protection hardware appropriate to the selected cell configuration; do not connect a bare cell directly to the module’s supply rail.
- Check that regulated rails can supply the load without excessive heat or voltage drop, including startup and peak demand.
- Measure current draw during an emulator workload and at the screen brightness and audio level you expect to use.
- Test low-battery detection and shutdown behavior before relying on the device to protect its storage.
A single-cell boost design and a multi-cell buck or buck-boost design involve different charger, conversion and safety requirements. The right choice depends on the selected cells and load; the supplied evidence does not establish one circuit as best for every build.
Rank #3
- Upgraded processor BCM2712, quad-core Cortex-A76 64-bit SoC, more powerful performance
- Faster eMMC Flash storage, up to 200 Mbps data rate
- Adopts B to B connectors, most compatible with Compute Module 4
- Onboard Gigabit Ethernet PHY supporting IEEE1588, suitable for network applications
- Onboard PCIe Gen 2 x1 interface, allows connecting more useful modules
Choose how the controls and audio connect
Simple buttons can be read through GPIO, while a microcontroller can handle button scanning and analog sticks, and can potentially report battery status or request a safe shutdown. The latter can simplify the CM4-side input design but adds firmware, another component to power and another subsystem to debug. Choose based on the controls and battery features you actually need, then test input behavior before packaging the electronics.
The Retro Lite CM4 reference design connected its controls through an Arduino input and added a USB hub because the internal USB connection was occupied and the design needed additional USB connectivity. This is a useful reminder to count internal as well as external USB devices when choosing a carrier and planning wiring.
Audio also takes space and power. Decide whether the build needs stereo speakers, a headphone jack, or both, then test the amplifier and switching behavior with the chosen power supply. In the Retro Lite build, an I2S WM8960 audio amplifier drove stereo speakers, and the headphone jack switched automatically.
Rank #4
- The power of Raspberry Pi 4 in a compact form factor for deeply embedded applications. Raspberry Pi Compute Module 4 incorporates a quad-core ARM Cortex-A72 processor, dual video output, and a wide selection of other interfaces.
- Raspberry Pi Compute Module 4 4GB RAM 0GB (Lite) CM4104000 comes with Gigabit Ethernet, 2.4GHz and 5.0GHz IEEE 802.11b/g/n/ac wireless, Bluetooth 5.0, BLE, with onboard and external antenna options.
- H.265 (HEVC) (up to 4Kp60 decode), H.264 (up to 1080p60 decode, 1080p30 encode),Energy-efficient Raspberry Pi runs silently and uses far less power than other computers.
- Broadcom BCM2711 quad-core Cortex-A72 (ARM v8) 64-bit SoC @ 1.5GHz,more powerful than earlier models.
- Package Includes: 1x Raspberry Pi Compute Module 4 CM4104000 4GB RAM 0GB (Lite) Single Board,1x Aluminum Alloy CNC Heat Sink with PWM Fan for Raspberry Pi CM4 Module
Budget for cooling and a serviceable enclosure
Emulation loads the processor for sustained periods, so check temperatures and performance inside the intended enclosure rather than relying on an open-board test. Leave space for the chosen heatsink and fan, airflow and battery wiring. A fan also adds a power draw and a potential noise source. Raspberry Pi’s CM4 datasheet lists H.265/HEVC decoding up to 4Kp60 and H.264 video capabilities; those video specifications do not establish how well a particular emulator or game will run.
Keep access to storage, connectors and fasteners in mind while laying out the case. A design that can be opened for cable changes or battery service is easier to debug and maintain than one that permanently traps the electronics behind the screen and controls.
Prototype in stages before committing to a custom build
- Select a CM4 SKU: choose the RAM, wireless configuration and Lite or eMMC storage arrangement for your software and library.
- Bring up the module: use a CM4 IO Board or compatible carrier to verify boot, networking, USB and basic operation before working on a handheld enclosure.
- Validate the display: test HDMI or DSI, confirm cable compatibility, and apply the appropriate display setup for the chosen panel.
- Add controls and audio on the bench: test button, stick and sound behavior before integrating them into a compact assembly.
- Measure the load: run the intended software and measure power use with the display, audio and cooling operating as expected.
- Integrate battery and cooling: validate charging, protection, regulated power, thermal behavior and controlled shutdown.
- Design the compact carrier and enclosure: finalize their dimensions after the electrical interfaces, cable routes and component positions are stable.
What the Retro Lite CM4 demonstrates—and what it does not
Raspberry Pi’s project report dated 28 March 2022 describes the Retro Lite CM4, a completed handheld reference using a 5.5-inch LCD, a 4000mAh battery, a custom control and audio PCB, a copper heatsink and fan, and a USB hub. The makers reported about four hours of battery life and full-speed Dreamcast and PSP emulation on that build. These are results reported for that specific console, not guarantees for another CM4 handheld.
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Runtime and emulation performance can change with battery capacity, display brightness, workload, volume, cooling and power-conversion efficiency. The CM4’s video decode specifications should not be treated as a promise of emulator speed: results also depend on emulator software, settings, the game and thermal limits. The available evidence does not provide an independent benchmark that would make the Retro Lite figures a general prediction for other builds.
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