Sigh ... I've used PIC's for years.  But for this project I'm giving them up.  The reason is that PIC's are just not very open-source friendly.  I'm going to use Arduino Nano's from now on instead of PIC's.  They're just a few dollars each, and you can't beat the user-friendly programming.    Not so with using advanced PIC's under Linux...  I'll waste more time coming up to speed on Linux/PIC tool chains that it would take to simply replace the microcontroller.