Omitting diacritics on a display with limited character set

Question

I have to display French on a display with fixed/limited character set. It is missing all the capital letters with diacritics. Specifically:

À Â È Ê Ë Î Ï Ô Ù Û

Do the graves only indicate pronunciation or or also semantics? Would it be fine to just substitute those chars with A I E O U or do I need to take special considerations?

PS: The context is pretty specific. The display is used on campsites to control devices like showers, door access etc. So it displays messages like "Remaining credits/time", "Access granted", "Press button to start/stop" and things like that. The display has two lines with 16 chars each, so text has to be kept brief.
It would be OK for me if it is just bad practice to omit the diacritics. It may not be OK, if chances are high, that people get confused by wrong meaning.

Answer 1

Diacritics are typographically mandatory on capital letters but you are in an obvious case where you have no other choice than missing them and use the unaccented letters. Dynamic traffic signals have the same issue, e.g.:

That should read "TRACÉ MODIFIÉ"

^{Image credits: https://www.ttsys.fr/library/catalogue/tts-catalogue-its.pdf}

It is very unlikely for it to be an issue in the context you describe. In fact, a lot of native French people were or are still taught at school diacritics aren't required on capital letters, so won't be surprised at all.

See anyway: Accentuation des majuscules — Accents on upper-case letters