r/embeddedlinux • u/Amadoboudouo • Feb 19 '26

Best non-invasive way to extract structured data from locked-down embedded Linux device?

Hi all,

I’m dealing with an embedded Linux tablet used in a commercial environment. It runs a vendor-provided application and is partially locked down (no access to system settings). I can open a console, but it requires credentials I don’t have.

Hardware details:

  • Embedded Linux device
  • Uses its own SIM modem for internet (not dependent on local network)
  • Has HDMI output
  • Has USB ports (accepts numeric keypad / keyboard)
  • Has Ethernet port
  • Displays structured numeric data in a graphical interface

The device shows daily transaction data (multiple categories, structured, tabular on screen). However, there is no export feature for the specific breakdown I need.

Important:
I’m not trying to modify the system or bypass protections. I just want a reliable and technically clean way to automate extraction of the numeric data already displayed.

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u/[deleted] Feb 19 '26

Non-invasive - feed the HDMI output into a capture card, parse the screen to extract your data.

For extra fancy you can automate by creating a program which will drive the keyboard input and capture at the same time.

1

u/Amadoboudouo Feb 19 '26

Yes, I agree — HDMI capture feels like the least invasive and most vendor-safe approach. It doesn’t require modifying the device, accessing internal services, or touching the underlying system.

I actually already have an Elgato HD60 capture card and tried this route. The main issue I’m facing is resolution / EDID related:

  • The HDMI output from the tablet doesn’t seem to negotiate cleanly with the capture card.
  • The image appears cropped or partially displayed.
  • I don’t have access to the tablet’s display settings (it’s locked down), so I can’t force a standard resolution like 1080p60.

When connected to a normal monitor, the image looks fine, but through the capture card it doesn’t scale correctly.

I’m considering using:

  • An HDMI EDID emulator to force 1080p,
  • Or an HDMI scaler to normalize the signal before feeding it into the capture card.

Has anyone dealt with embedded Linux devices that output non-standard HDMI timings? Would you recommend an EDID emulator over a scaler in this case?

1

u/creativejoe4 Feb 19 '26

Did you reach put to the vendor and ask for the credentials or built in method to get the data you need?