import firebase_admin, time
from firebase_admin import credentials
from firebase_admin import firestore
from threading import Event
from serial import Serial
ser = Serial('/dev/ttyACM0', 9600)

cred = credentials.Certificate('insert-firebase-cert-here.json')
firebase_admin.initialize_app(cred)

db = firestore.client()

# Create a callback on_snapshot function to capture changes
def on_snapshot(doc_snapshot, changes, read_time):
    for doc in doc_snapshot:
        print(u'Received document snapshot: {}'.format(doc.id))
        packet = doc.to_dict()
        az = packet['AZ']
        el = packet['EL']
        sendstring = "W" + az + " "+ el + "\r\n"
        print("Moving to AZ=" + az + ", EL=" + el)
        ser.write(str.encode(sendstring))

doc_ref = db.collection(u'stations').document(specify-stationId)

# Watch the document
doc_watch = doc_ref.on_snapshot(on_snapshot)

Event().wait()