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https://github.com/k0rventen/avea

Control Elgato's Avea bulb using python3 !
https://github.com/k0rventen/avea

bluepy bluetooth-low-energy elgato-avea hacktoberfest python3 reverse-engineering

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Control Elgato's Avea bulb using python3 !

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# Control of an Elgato Avea bulb using Python



[![PyPI](https://img.shields.io/pypi/v/avea.svg)](https://pypi.org/project/avea/)

[![Language grade: Python](https://img.shields.io/lgtm/grade/python/g/k0rventen/avea.svg?)](https://lgtm.com/projects/g/k0rventen/avea/context:python)

[![Build Status](https://travis-ci.com/k0rventen/avea.svg?branch=master)](https://travis-ci.com/k0rventen/avea)



The [Avea bulb from Elgato](https://www.amazon.co.uk/Elgato-Avea-Dynamic-Light-Android-Smartphone/dp/B00O4EZ11Q) is a light bulb that connects to an iPhone or Android app via Bluetooth.



This project aim to control it using a Bluetooth 4.0 compatible device and some Python magic.



Tested on Raspberry Pi 3 and Zero W (with integrated bluetooth). 



- [Control of an Elgato Avea bulb using Python](#control-of-an-elgato-avea-bulb-using-python)

  - [TL;DR](#tldr)

  - [Library usage](#library-usage)

  - [Code documentation](#code-documentation)

  - [Reverse engineering of the bulb](#reverse-engineering-of-the-bulb)

  - [Communication protocol](#communication-protocol)

    - [Intro](#intro)

    - [Commands and payload explanation](#commands-and-payload-explanation)

    - [Color command](#color-command)

    - [Brightness command](#brightness-command)

  - [Walkthrough & Example](#walkthrough--example)

    - [Brightness](#brightness)

      - [Color](#color)

  - [Python implementation](#python-implementation)

    - [One-liner for color computation](#one-liner-for-color-computation)

    - [Bluepy writeCharacteristic() overwrite](#bluepy-writecharacteristic-overwrite)

    - [Working with notifications using Bluepy](#working-with-notifications-using-bluepy)

  - [TODO](#todo)



## TL;DR



The lib requires [bluepy](https://github.com/IanHarvey/bluepy), so we must install the following dependancy, wheter we use pip or install from source.



**Dependancies**



```

sudo apt install libglib2.0-dev

```



**Then install from pip3**



```bash

sudo apt install python3-pip

sudo pip3 install --upgrade avea

```



**or if you prefer installing from source**



```bash

git clone https://github.com/k0rventen/avea

cd avea

sudo python3 setup.py install

```



## Library usage



You can check the example script `example.py`, to try it directly onto your bulbs :



```bash

sudo python3 example.py

```



Below is a quick how-to of the various methods of the library.



**Note : the discover\_avea\_bulbs() function needs root privileges, due to bluepy's scan(). From your user, you can use sudo -E.**



```python

import avea # Important !



# Get nearby bulbs in a list, then retrieve the name of all bulbs

# using this method requires root privileges (because of bluepy's scan() )

nearbyBulbs = avea.discover_avea_bulbs()

for bulb in nearbyBulbs:

    bulb.get_name()

    print(bulb.name)



# Or create a bulb if you know its address (after a scan for example)

myBulb = avea.Bulb("xx:xx:xx:xx:xx:xx")



# You can set the brightness, color and name

myBulb.set_brightness(2000)                 # ranges from 0 to 4095

myBulb.set_color(0,4095,0,0)                # in order : white, red, green, blue

myBulb.set_rgb(0,255,0)                     # RGB compliant function

myBulb.set_smooth_transition(255,255,0,4,30)   # change to rgb(255,255,0) in 4s with 30 iterations per second

myBulb.set_name("bedroom")                  # new name of the bulb



# And get the brightness, color and name

print(myBulb.get_name())                # Query the name of the bulb

theColor = myBulb.get_color()           # Query the current color

theRgbColor = myBulb.get_rgb()          # Query the bulb in a RGB format

theBrightness = myBulb.get_brightness() # query the current brightness

theAddr = myBulb.addr                   # query the bulb Bluetooth addr

theFwVersion = myBulb.get_fw_version()  # query the bulb firmware version

```



That's it. Pretty simple.



Check the explanations below for more informations, or check the sources !



## Code documentation



## Reverse engineering of the bulb



I've used the informations given by [Marmelatze](https://github.com/Marmelatze/avea_bulb) as well as some reverse engineering using a `btsnoop_hci.log` file from an Android device and Wireshark.



Below is a pretty thorough explanation of the BLE communication and the python implementation to communicate with the bulb.



As BLE communication is quite complicated, you might want to skip all of this if you just want to use the library. But it's quite interesting.



## Communication protocol



### Intro



To communicate the bulb uses Bluetooth 4.0 "BLE", which provide some interesting features for communications, to learn more about it go [here](https://learn.adafruit.com/introduction-to-bluetooth-low-energy/gatt).



To sum up, the bulb emits a set of `services` which have `characteristics`. We use the latter to communicate to the device.



The bulb uses the service `f815e810456c6761746f4d756e696368` and the associated characteristic `f815e811456c6761746f4d756e696368` to send and receive informations about its state (color, name and brightness). We'll transmit over this characteristic.



### Commands and payload explanation



The first bytes of transmission is the command. A few commands are available :



Value | Command

--- | ---

0x35 | set / get bulb color

0x57 | set / get bulb brightness

0x58 | set / get bulb name



### Color command



For the color command, the transmission payload is as follows :



Command | Fading time | Useless byte | White value | Red value | Green value | Blue value

---|---|---|---|---|---|---



Each value of the payload is a 4 hexadecimal value. (The actual values are integers between 0 and 4095)



For each color, a prefix in the hexadecimal value is needed :



Color | prefix

---|---

White| 0x8000

Red | 0x3000

Green | 0x2000

Blue | 0X1000



The values are then formatted in **big-endian** format :



Int | 4-bytes Hexadecimal | Big-endian hex

---|---|---

4095 | 0x0fff| **0xff0f**



### Brightness command



The brightness is also an Int value between 0 and 4095, sent as a big-endian 4-bytes hex value. The transmission looks like this :



Command | Brightness value |

---|---

0x57 | 0xff00



## Walkthrough & Example



Let say we want the bulb to be pink at 75% brightness :



### Brightness



75% brightness is roughly 3072 (out of the maximum 4095):



Int | 4-bytes Hexadecimal | **Big-endian hex**

---|---|---

3072 |0x0C00| **0x000C**



The brightness command will be `0x57000C`



#### Color



Pink is 100% red, 100% blue, no green. (We assume that the white value is also 0.) For each color, we convert the int value to hexadecimal, then we apply the prefix, then we convert to big-endian :



Variables | Int Values | Hexadecimal values | Bitwise XOR | Big-endian values

---|---|---|---|---

White| 0| 0x0000| 0x8000| 0x0080

Red | 4095| 0x0fff| 0x3fff| 0xff3f

Green | 0 | 0x0000| 0x2000 | 0x0020

Blue | 4095| 0x0fff | 0x1fff| 0xff1f



The final byte sequence for a pink bulb will be :



Command | Fading time | Useless byte | White value | Red value | Green value | Blue value

---|---|---|---|---|---|---

`0x35`|`1101`| `0000`| `0080`|`ff3f`|`0020`|`ff1f`



## Python implementation

Below is some python3 code regarding various aspects that are quite interesting.



### One-liner for color computation

To compute the correct values for each color, I created the following conversion (here showing for white) :



```python

white = (int() | int(0x8000)).to_bytes(2, byteorder='little').hex()

```



### Bluepy writeCharacteristic() overwrite

By default, the btle.Peripheral() object of bluepy only allows to send UTF-8 encoded strings, which are internally converted to hexadecimal. As we craft our own hexadecimal payload, we need to bypass this behavior. A child class of Peripheral() is created and overwrites the writeCharacteristic() method, as follows :



```python

class AveaPeripheral(bluepy.btle.Peripheral):

    def writeCharacteristic(self, handle, val, withResponse=True):

        cmd = "wrr" if withResponse else "wr"

        self._writeCmd("%s %X %s\n" % (cmd, handle, val))

        return self._getResp('wr')

```



### Working with notifications using Bluepy

To reply to our packets, the bulb is using BLE notifications, and some setup is required to be able to receive these notifications with bluepy.



To subscribe to the bulb's notifications, we must send a "0100" to the BLE handle which is just after the one used for communication. As we use handle 0x0028 (40 for bluepy) to communicate, we will send the notification payload to the handle 0x0029 (so 41 for bluepy)



```python

self.bulb.writeCharacteristic(41, "0100")

```

After that, we will receive notifications from the bulb.



## TODO

- Reverse engineer the `ambiances` (which are mood-based scenes).