Ledslie

Projects
Participants	Chotee, Thijs
Skills	electronics, microcontrollers, linux, mqtt, webservices, python, twisted, ansible
Status	Active
Niche	Electronics
Purpose	Infrastructure

Interface to display information

• It is a Grayscale display of 144x24 pixels that displays information.
• It lives at http://ledslie.ti/ and is accessible at the space via a website and MQTT.

Interfaces

• At http://ledslie.ti/ you to submit content, such as animated GIFs, from your browser.
• You can publish content by posting content to the web-service.
• You can publish content directly to the mqtt broker that lives on ledslie.ti:1883.

Known issues (and their solution)

• Symptoms: The screens network dependent screens are missing, time might be incorrect. http://ledslie.ti is not available.
• Problem: The DHCP server was not available when Ledslie started up, and is now in network-less mode. Likely there was a space power failure.
• Solution: Once the network is stable again, cycle the power of Ledslie, it should restart properly.

Content ideas (in no specific order)

• (Done-ish) Spacealert with message. Still missing working shardik code.
• IRC integration via shardik: .display [message]
• (Done) MPD songs: What are we listening to?
• Wifi SSIDs being broadcast / MAC count stats
  • https://arstechnica.com/information-technology/2014/11/where-have-you-been-your-smartphones-wi-fi-is-telling-everyone/
  • https://www.hak5.org/episodes/haktip-23
• (Done) Next and tram / metro / nightbuses
• (Done) Incoming rain alerts (https://www.buienradar.nl/overbuienradar/gratis-weerdata, https://br-gpsgadget-new.azurewebsites.net/data/raintext/?lat=52.35&lon=4.83)
• (Done) Clock
• (Done) Midnights ("Midnight in «City»")
• Days until Brexit
• Drama stats
  • Parse the ML archives, get stats from there --- https://techinc.nl/cgi-bin/mailman/listinfo/ + https://techinc.nl/cgi-bin/mailman/listinfo/discuss
  • Keep track of IRC stats --- https://gist.github.com/habnabit/5823693
• API/Interface for countdowns.
• (Done) Next TI events
• Space events
  • Next interesting rocket launch (SpaceX, Soyuz, etc...)
  • ISS flyovers
• (Done) Zonsopkomst en -ondergang tijden
• (Done) Maan standen. volle maan, nieuwe, etc.
• External content
  • (Done) Btc/Eth values --- https://www.cryptocompare.com/
  • https://radar.squat.net --- https://0xacab.org/radar/drupal-make/wikis/api/1.1/notes
  • Security.nl
  • http://www.apiblog.nl/
  • Theregister.co.uk
  • hackernews.
  • Radio Yerevan Jokes: https://duckduckgo.com/Radio_Yerevan_jokes?iax=1&ia=about
  • Random Jargon file entries

How it works

Wifi --RF> Getchip --USB2> Teensy --[data,clock,latch]> Led-pannel

The led-panel takes 20V DC as input. At full output it's pulling about 4A, or about 80W. There's a small switcher-board that supplies the 5v the the getchip and Teensy from those 20V.

The Teensy drive code is here: https://github.com/techinc/ledmatrix/tree/master/ledmatrix144x24

The Ledslie code can be found here: https://github.com/techinc/ledslie

Software

The system's software is available at https://github.com/techinc/ledslie , this repo contains code that's running on the Display.

Possible Hardware expansions

• Add another panel by adding a USB2 hub, and modding another of the led panels with the teensy taking over the driving logic.

FAQ

• Q: What's that noise? A: The panel is being driven at rates way beyond the original design and we're well in the audible frequencies with the refresh-rates and some components are merrily humming along.
• Q: Why are some points brighter then others? A: Turns out that LEDs do wear. In their previous life some LEDs were on for years, while others were always off. There's plans to compensate for this in software.