Look at the pretty lights...
...whilst I'm invading your private lives and stealing your freedom.
The news that Rob Joyce, former head of the NSA's elite hacking squad and now White House cybersecurity coordinator, was giving a talk at the Shmoocon infosec conference raised hopes he would offer up some juicy insights into the surveillance state or Donald Trump's cyber policies. Instead Joyce talked about his very unusual …
Possibly the most already-done-a-million-times and boring thing you could do as a geek/hacker.
I mean, yeah, sure, it's fun for him. But even with the FM bit this isn't new to anyone. There are guys all over the Internet doing this, and a million times better, and with the same kind of local broadcasting of accompanying music.
My first question is not about the radio, as such, but: Did he pay for the broadcast rights and the right to use the Peanuts imagery? Probably not a good idea to tell everyone at a conference / on the Internet that you did that stuff as there's almost certainly a rightsholder waiting to complain somewhere once they see that.
I was much more intrigued by the DVDs you can get and project on-loop onto a thin bit of fabric in the window to do everything from showing a mystery Santa leaving presents to scary ghosts walking past the window every now and then - all synced together for each window in the house.
I thought that the Raspberry Pi wasn't suitable for driving addressable LED displays - as it is non-deterministic? Arduino controllers are able to be deterministic when driving the critically timed serial data streams.
My display this year had nearly 9000 LEDs. According to the inline power meter it was averaging about 160 watts at 250vac.
The PiDP-8 that I saw at the National Museum of Computing last thusday had another IC to drive the LED's used in the 'Blinkenlights' display.
Here is the explanation as to why this is.
Another point: the GPIO of the Raspberry Pi cannot deliver much current. As long as each led's current is limited by a 1K resistor, all is well. But that only delivers 1mA of current through the leds. Bright enough for a front panel, but just barely so. To let the leds burn brighter, all the ledRow pins on the GPIO connector are buffered through a UDN2981A driver chip. That way, resistors of around 390K can be used to light up the leds much brighter. The UDN2981A has 8 inputs, connected to the GPIO, and switches its 8 outputs based on the signal it receives from the 8 GPIO pins. This driver chip can deliver much more current, and is fed on the 5V power line from the GPIO connector (note that everything else on the Pi and on the front panel is 3.3V). The voltage drop from this chip, and from the leds behind it means the GPIO pins on the other end of the schematic do not get exposed to the dangerous 5V levels - in fact, no more than 1.7V or so reaches them.
"Another point: the GPIO of the Raspberry Pi cannot deliver much current. "
Addressable LED strips don't need much drive from the controller. WS2812B LEDs are fed 5vdc from several power supplies - each psu delivering about 3A to a single 5 metre strip (150 LEDs). The LEDs' data/clock signals are daisy-chained in series.
The controller just has to supply enough power to drive the data/clock signal line for the first LED. Each LED then draws its power from its strip's psu - and propagates the data/clock signal to the next in series.
Basically it is loading a large shift register - operating fast enough that each LED gets its own individual colour/brightness setting without noticeable flicker. The controller then creates the patterns by choosing the appropriate mixes of colours, intensities, and changes.
The length of a daisy-chain is limited by the number of shifts before the process becomes visible. The usual cheap controllers handle chains of up to 2048 LEDs
Only important for multiple Pis working asynchronously.
If it really burns your toast, switch to Baeglebone Black hardware. You get two microcontrollers a-la Arduino AND a Linux computer with which to push stuff at them on every motherboard. Also Multiplexors and other good stuff.
But for a garden light display? A bit of overkill.
By the time the legal eagles get into action, he will have removed the lights. Just as well. Given that Disney routinely sends in the troops when day care centres put Disney characters on their walls without permission, it would be only a matter of time before the owners of the rights to Peanuts characters came after this guy.
The FCC allows you to broadcast on both the FM and AM band provided the emitted power doesn't exceed a maximum value and doesn't cause noticeable interference to a licensed station. Back in the day I used to use a small FM transmitter to broadcast music around the house and yard during parties (you'd just grab a few old boomboxes and put them in strategic locations to play the music). I still have the kit but its fallen into disuse because analog radio has largely been supplanted by digital feeds, feeds that include WiFi connected loudspeakers.
(The transmitter itself is quite high quality; its basically a single chip that has a frequency synthsizer and stereo modulator. I'd guess a real FM transmitter is just this chip plus an audio limiter and R/F power amplifier.)
In Oz we have similar restrictions. At one charity event I work with we had some people working in the AV control room who supply Clubs and licensed venues with transmitters for In-House TV on a public access channel. We setup one of the transmitters in the AV centre to transmit to the TVs (and large screens) we had around the venue. We attached the transmitter to a small domestic TV antenna. When the local community radio station wanted to rebroadcast the audio from our feed using their OB setup we gave them a HD Set-top box and indoor antenna to tune into the broadcast. The set-top box wouldn't find the channel using the Auto-scan function so we manually tuned it in. The signal was so strong it was overpowering the auto-tune function. The set-top box was 200m away from the transmitter and was able to clearly pickup the signal without the antenna attached.
We worked out that anyone in the immediate area (several Km square) who auto-tuned their TV or Set-top while we were broadcasting would have been able to view our feed.
There's a guy in our town who does this. My kids wanted me to do it this year and I seriously considered it. I decided not to on the grounds that last time I put up any significant number of Christmas lights they stayed up for three years. Kinda like how my parents tend to have a nativity scene in their front yard from the beginning of December till around Easter every year.
"I decided not to on the grounds that last time I put up any significant number of Christmas lights they stayed up for three years."
A nearby house has a garden full of Xmas figures which haven't been lit for a couple of years now. It is difficult to see where they would have had the space to store them
I resist leaving things up too long as the sunlight tends to destroy any plastic. Some light sets include iron that rusts quite quickly - and copper suffers from electrolytic corrosion in the damp. IP65/7 ratings seem to be rather optimistic.
Next year will be time to downsize my Halloween/Xmas decorations from quantity to a few custom driven effects. It is starting to be a time consuming exercise from the middle of September until the end of January. I now understand how the people behind the Blackpool Illuminations must feel. I blame them for influencing me in my childhood.
Even the Halloween decorations are not all packed away yet. However a neighbour's 3 year old would be very disappointed if the dropping spiders were removed. Every time the door is opened he wants to see them drop in response to a hand clap. He always backs away in apparent horror - followed by a big grin. We have reached a count of 1-2-3 - so it will be interesting to see how well his counting progresses.
Yesterday a neighbour asked me if I could build some light decorations for a school's Valentine's Day party. Then at Easter she will want the childrens' barbeque set up and decorated as usual.
Sometimes it feels like the Flanders and Swann song about "the gas man cometh" - or the task of Sisyphus.
How about, instead of telling us how to light up LEDs, you tell us how you went about securing the nation's most critical national security networks from foreign adversaries?
Oh... that's right... you didn't, and they got right in, and spread your tools onto the darknet, allowing for endless numbers of cyber attacks against a global population of systems with zero protection thanks to the NSA's lack of disclosure to OS vendors, opting rather to weaponize flaws instead of securing systems. Maybe I should be the one doing his job. From the sound of his presentation, I've got all the credentials I need, and more skills to boot!
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