https://danielmangum.com/posts/laptop-hdmi-monitor-sbc/

Daniel Mangum [ ]

  * [RISC-V Bytes]
  * [RISC-V Tips]
  * [Blog]
  * [About]

Using a Laptop as an HDMI Monitor for an SBC

October 9, 2025 2-minute read

Though I spend the majority of my time working with microcontroller
class devices, I also have an embarassingly robust collection of
single board computers (SBC), including a few different Raspberry Pi
models, the BeagleV Starlight Beta (RIP), and more. Typically when
setting up these devices for whatever automation task I have planned
for them, I'll use "headless mode" and configure initial user and
network credentials when writing the operating system to the storage
device using a tool like Raspberry Pi's Imager.

However, sometimes direct physical access to the SBC with a monitor
and keyboard is useful for initial configuration, maintenance
operations, or workloads that have a visual component. As someone who
doesn't use any external monitors^1 for my daily development, digging
up an HDMI monitor, finding somewhere to put it, and connecting it to
the device is an annoying process. Furthermore, if I'm on the go I
almost certainly don't have easy access to an external monitor.

laptop-hdmi-monitor-0


    Raspberry Pi boot logs shown in VLC media player.

Fortunately, I rarely ever do this because I have a handful of HDMI
to USB capture cards, ranging from extremely cheap variants from
Amazon, to the higher quality Elgato Cam Link 4k. These are typically
used for live streaming a video feed from DSLR / mirrorless cameras
or gaming consoles, but they also serve as a great option for
capturing video from any other device that has HDMI output. On my
System76 Linux daily driver laptop, I can use any number of different
video playback applications to display the HDMI output via the
capture card. For longer term use cases, I can breathe new life into
one of my old laptops, using the capture card to effectively convert
it into a monitor.

VLC media player:

vlc v4l2:///dev/video0

FFplay (FFmpeg):

ffplay /dev/video0

Cheese:

cheese v4l2:///dev/video0

If you do want to stream or record the SBC output, OBS will give you
even more control. You'll still need a USB keyboard, but I already
use one with my laptop, so temporarily plugging it into the SBC for
configuration while I use the laptop as a monitor is minimally
disruptive. However, if you find yourself regularly needing to
connect to multiple machines, it might be time to consider getting a
KVM switch.

---------------------------------------------------------------------

 1. Yeah, I just sit here with my one laptop screen. Can you believe
    that? -[?]

(c) 2025 Daniel Mangum * Powered by Hugo & Coder.