it's been a while, do-178 is concerned with software while do-254 is hardware (both for aviation, FAA standards). Depending on the criticality of the component (e.g. engine control vs radios vs entertainment system) they will abide by different levels (ie DO-178A ... DO-178E).

For both software and hardware there will be requirements for documentation, design, verification, and testing. Some even go as far as to requir the implementation of certain functional logic in multiple ways and having concensus logic (eg hardware logic to interpret GPS accuracy/confidence That ends up being broadcast externally).

There's also DO-160 that's concerned with environmental requirements (eg temperature, humidity, lighting).

This is what makes a radio that should cost $300, cost $5000, and why FAA certified aviation components are expensive compared to uncertified components (eg hobby airplane builds).