This is an actively maintained, platform-agnostic C library for embedded UDS.
For developers looking to implement UDS without building the entire stack from scratch, GitHub hosts several highly reliable open-source libraries. These libraries handle SID parsing, negative response handling, and session timeouts. Popular Open-Source UDS Repositories iso 142291 pdf github new
There are several noteworthy open-source implementations and resources for ISO 14229-1 (Unified Diagnostic Services) This is an actively maintained, platform-agnostic C library