Sunrise Machine with the Tessel 2
lyzadanger 
Setup
If you'd like your Sunrise Machine to be able to tweet, you'll need to obtain Twitter API credentials. You'll have to fill out a little form, but the use of the API is free. Once you're signed up, you'll have access to an API/developer dashboard. You'll need to find the following four things to make your Sunrise Machine talk to Twitter:
- Consumer Key
- Consumer Secret
- Access Token (Key)
- Access Token (Secret)
Access Token (Key) and Access Token (Secret) may need to be generated (you just to have to click a button to do it). Each of the four credentials are long strings. Copy and paste them somewhere safe.
For my Sunrise Machine, I created an entirely new Twitter user, but you can use your main Twitter account if you prefer. Or, if Twitter isn't your thing, you can disable it completely with a configuration value (more on that soon).
Webcams and Calibration
In the course of building the Sunrise Machine, I discovered that some webcams require a period of "warmup" before capturing stills so that they can calibrate the correct exposure. This usually takes 2-3 seconds. Without calibration "warmup", images taken of bright scenes—like outside—would result in all-white images. Yikes! The Sunrise Machine's software can automatically calibrate your webcam before capturing images to help you get the best images possible. You can disable this feature if you like (see the configuration section below).
USB and the Tessel
Working with a USB thumb drive and USB camera on a Tessel is eerily easy.
For the thumb drive: make sure it is formatted as Fat32 or something similar (MS-DOS FAT, ExFat—not Mac OS Extended). The Sunrise Machine will write files (images, movies and GIFs) directly to your thumb drive. If you're curious, a mounted USB thumb drive can be accessed at /mnt/sda1 on the Tessel's file system. Use the t2 root command if you want to ssh in to your Tessel and have a look around the filesystem—the Tessel 2 runs OpenWRT Linux.
Similarly, plugging in a USB webcam to a Tessel makes the device available at /dev/video0.
The Tessel and Time
The Tessel 2 isn't an independent timekeeper. Once the Tessel has power and its OpenWRT Linux boots, it will attempt to connect to an NTP (Network Time Protocol) server to obtain the current time. There are a couple of things to note about this. One, dates and times on the Tessel are UTC times—it doesn't know about your local timezone. Second, the Tessel can't tell what time it is at all if it does not have a network connection (i.e. if it's only tethered to your computer over USB but is not connected to your LAN).
The command t2 list will show you all nearby Tessels and how they are connected, e.g. for my Tessel, which I've named ichabod after a local early settler of my town named, improbably, Ichabod Onion:
$ t2 list
INFO Searching for nearby Tessels...
USB ichabod
LAN ichabod
ichabod is, in this case, connected both to my USB port and my local WiFi network. Good. It'll know what time it is. In UTC, at least.