Since you are going to use wind as your power source, you'll want to know both the direction and strength of the wind. You can do this with an analog wind sensor. Here is a picture of a wind sensor from https://moderndevice.com/product/wind-sensor/, that is fairly inexpensive:
You can mount it to the mast if you like; perhaps use a small piece of heavy duty tape and mount it to the top of the mast. In order for the BeagleBone Blue to talk with this, you need to connect it to the GPIO connector pins. The following is a close-up of the connections that the wind sensor requires:
You'll need a GND and +V
