A Day with Philips Hue

I got a Philips Hue on the first day it was available at the Apple Store and had f.lux running 3 hours later. Here are my notes.

Some notes about Hue in general:

1. Color is great, whites look good
2. Bulbs are efficient (8.5W)
3. Brightness is good, useful as a regular bulb.

Negatives:

1. The controller rate-limits updates from the software. So if you wire up a slider to send messages at 10fps, it won't work. You can send 2-3 messages per second, and then it does some interpolation on its own, which might not give the "look" you want.
2. Powering down a bulb (like with a lightswitch) and restarting loses all the bulb's state! Depends on a client to restore it. The controller bridge really should do this automatically.
3. Range isn't so great -- Zigbee loses to my DECT phones and baby monitor and wireless network. So you really need a "mesh" of nodes, not two bulbs 50 feet away.
4. Minor: Bulbs have a front-facing distribution (put out less light to the side and back than the L-Prize bulb.)

Here are some notes about the interface to the Hue controller (I didn't look into the Zigbee side, just sniffed the iOS client.)

Discovery

Hue uses SSDP (like Roku and Sonos do). So, discovery is pretty standard. You can also walk your class-C network and look for a webserver responding to /description.xml, which is cheating (but it works.)

Authentication

Hue relies on client-generated secrets. Each client generates a secret (likely one of the device unique identifiers), and then uses that to talk to the hub.

So you'll see an http request like this:

GET /api/{secret}/lights HTTP/1.1

And the switch will respond "unauthorized user." The client will then start polling to make a user:

POST /api
{"username": "{secret}", "devicetype":"{name}"}

And Hue will respond (in JSON):
"link button not pressed"

Once the button is pressed:
"success"

Basic Controller

The current iOS client appears to poll /api/{secret} once per second, which gives the whole dump of settings. Most of these seem writable.

To change a light you do a PUT to /api/{secret}/lights/#/state (not POST).

(where # is a number you found from the main lights feed. On the default kit you'll have lights 1-3 available.)

Contents are JSON! For single brightness and color settings (not groups or scenes) you might see something like this:

{"bri": 128, "ct": 200, "on": true}

Brightness appears to go to 255, color temperature is 500 to 154 (which corresponds roughly to 2100K to 5800K, somewhat nonlinear.)

Or you can send xy coordinates to control the bulb in color (use your handy sRGB to XYZ matrix):

{"bri": 255, "xy":[0.4, 0.4], "on": true}

You must rate limit your client in the range of 2-3 updates per second, or the hub will send you a 503 and throw away your changes. It appears to be "worth it" to stay in this range, or the rate limits get a little more severe.

Advanced Controller [TBD]

The software has the ability to define groups and scenes. Have not investigated yet.