This blog post outlines a highly portable and convenient method for accessing the video output of Single Board Computers (SBCs), such as the Raspberry Pi, without needing a dedicated external monitor. The author, who frequently works in headless mode but occasionally requires direct physical access for configuration and maintenance, proposes using an HDMI to USB capture card (like the Elgato Cam Link 4k or cheaper alternatives). By plugging the capture card into a laptop, the SBC’s video feed can be displayed instantly using standard video playback software (e.g., VLC, FFplay, or Cheese on Linux). This technique effectively converts the laptop into a monitor, minimizing disruption and offering a crucial solution for on-the-go troubleshooting and setup.
Using a Laptop as an HDMI Monitor for an SBC: Summary
Problem Statement: The author, who works with numerous SBCs (including Raspberry Pi and BeagleV Starlight), finds it inconvenient to locate and set up an external HDMI monitor when physical access to the device (beyond headless mode) is required, particularly while traveling.
The Solution: The strategy involves utilizing an HDMI to USB capture card, which are typically designed for streaming video from DSLR cameras or gaming consoles, to capture the SBC’s video feed.
Mechanism & Hardware: Capture cards, such as the high-quality Elgato Cam Link 4k or less expensive Amazon variants, convert the HDMI output into a USB stream readable by the laptop.
Software for Display (Linux Examples): On a Linux operating system (specifically mentioned on a System76 daily driver), the output (/dev/video0) can be viewed using common video players:
VLC media player: vlc v4l2:///dev/video0
FFplay (FFmpeg): ffplay /dev/video0
Cheese: cheese v4l2:///dev/video0
Key Takeaway (Setup Convenience): This method effectively breathes new life into an old laptop or utilizes a current machine to serve as a portable monitor. While a separate USB keyboard must still be plugged into the SBC, the overall setup is considered minimally disruptive.
Advanced Control: For users needing to stream or record the SBC's output, OBS (Open Broadcaster Software) provides comprehensive control.
Alternative Consideration: If the user regularly needs to connect to multiple machines, investing in a KVM switch is suggested.