One of the few things I don't like about the BeBoPr board is since it pre-dates the BeagleBone Black it conflicts with a bunch of pins that are now reserved for the new on-board HDMI and 2G eMMC.
Fortunately, Bas has released the BeBoPr-Bridge board, which is a set of boards that shuffles around the I/O pin-out and allows an otherwise stock BeBoPr to work with a BeagleBone Black without causing any pin conflicts. The Bridge board even solves the problem of how to access the serial boot console when using the BeBoPr!
Thanks to the folks at OSH Park, I was able to get three sets of the Bridge board fabricated and shipped to me for a total cost of $23.10 (including shipping), or about $7 each! Once the boards arrived and I got them built up, it was time to print something stand-alone using the BeagleBone Black and my $79 eBay special HDMI monitor:
If you want to follow along, make sure you're using my latest MachineKit image (with the -bone23 kernel), and do a git pull to grab the latest configuration files from the MachineKit branch of LinuxCNC. Launch LinuxCNC with the BeBoPr-Bridge configuration, and make sure you have not disabled the HDMIN cape in uEnv.txt. The latest image comes setup properly by default (HDMI disabled, and HDMIN enabled), but if you have been using a stock BeBoPr board you probably have both versions disabled.
Here are a couple still photos, you can find more on my G+ page.
Complete system with the BeagleBone Black mounted on top of the BeBoPr using the Bridge Board.
Bridge board mounted on my BeagleBone Black with serial cable, USB mouser/KB receiver, and HDMI cable connected.