一个好的串行通讯协议/堆栈的嵌入式设备?

After writing several different custom serial protocols for various projects, I've started to become frustrated with re-inventing the wheel every time. In lieu of continuing to develop custom solutions for every project, I've been searching for a more general solution. I was wondering if anyone knows of a serial protocol (or better yet, implementation) that meets the following requirements:After writing several different custom serial p