Hi, I managed to get the CAN portion working following this forum <http://forum.codesys.com/viewtopic.php?f=26&t=7331> . It is about the same cape. At this site <http://store.codesys.com/codesys-control-for-beaglebone-sl.html?___store=en>, you have a document named getting started and there are indicated steps on how to configure and test UART on that cape. I would suggest you to use codesys for your application as it has built in Modbus RTU, at least for the testing purposes. On their forum <http://forum.codesys.com/index.php> there are some interesting topics on beaglebone and raspberry, so you can try your luck there. As I never tried the UART portion of that cape, I can't give you exact steps, but I hope this will help you.