@osmodia I'll try to write this down nicely at some point in the future
I have GND, 5v, and tx/rx connected between the pi and Heltec
Then you have to configure the pi to enable the serial port (I used raspi-config)
Then you can tell meshtastic or the bbs to use /dev/ttyS0 as the serial port (this port isn't tried by default for anything it seems)