illuddc.py

#!/bin/python

# author: Claudio Bräuer
# mail: contact at cvbrauer dot de

# python dependencies: requests, subprocess, time, json, sys
# system dependencies: dccutil

import subprocess
import requests
import time
import json
import sys

# set your private home assistant rest token
token = "SECRETTOKEN"
# set the sensor name that you want to query
sensor = "sensor.balcony_light_illuminance_lux"
# set the relevant json field name
field = "illuminance_lux"
# set host ip and port
host = "192.168.0.1:8123"
# set illuminance value at which the monitor is set to maximum brightness
illuminance_max = 10000
# set illuminance value at which the monitor is set to minimum brightness
illuminance_min = 500
# set maximum monitor brightness
brightness_max = 100
# set minimum monitor brightness
brightness_min = 20
# set query interval in seconds
interval = 60
# get the id of the corresponding ddc brightness parameter, typically it is 10
ddcattr = "10"
# verify TLS certificate? Set to false because of reasons
verifyTLS = False

headers = {'Authorization': 'Bearer ' + token, 'Content-Type': "application/json"}
target = "https://" + host + "/api/states/" + sensor

while True:
    # lazy catchall
    try:
        response = requests.get(target, headers=headers, verify=False).text
    except:
        continue
    # json to dict
    responseJson = json.loads(response)
    # for debugging purposes, print json to understand structure:
    #print(responseJson)
    # set corresponding dictionary path to field here, e.g "attributes"-> "illuminance_lux"
    illuminance_cur = responseJson['attributes'][field]
    
    # clamping the values to min or max
    if illuminance_cur <= illuminance_min:
        illuminance_cur = illuminance_min
    if illuminance_cur >= illuminance_max:
        illuminance_cur = illuminance_max
    
    # linear interpolation for target value
    brightness_target = int(((illuminance_cur - illuminance_min) / (illuminance_max - illuminance_min)) * (brightness_max - brightness_min) + brightness_min)
    
    # get current brightness
    spargs = ['ddcutil', 'getvcp', ddcattr]
    ret = subprocess.Popen(spargs, stdout=subprocess.PIPE)
    output = ret.communicate()[0].decode('UTF-8').replace(" ","")
    # validate output
    try:
        brightness_cur = int(re.findall("currentvalue=(\d+),", output)[0])
    except:
        continue

    # do nothing if brightness stays the same
    if brightness_cur == brightness_target:
        time.sleep(interval)
        continue

    # smooth brightness transition
    steps = brightness_target-brightness_cur
    for i in range(0, abs(steps)):
        brightness_cur += -1 if steps < 0 else 1
        spargs = ['ddcutil', '--sleep-multiplier', '.1', 'setvcp', ddcattr, str(brightness_cur)]
        subprocess.call(spargs)

    time.sleep(interval)