Kiwink: Visible Light Communication via phone camera/flash
kiwink.io
kiwink.io
> IrDA was popular on PDAs, laptops and some desktops from the late 1990s through the early 2000s. However, it has been displaced by other wireless technologies such as Wi-Fi and Bluetooth, favored because they don't need a direct line of sight and can therefore support hardware like mice and keyboards. It is still used in some environments where interference makes radio-based wireless technologies unusable.
> An attempt was made to revive IrDA around 2005[3] with IrSimple protocols by providing sub-1-second transfers of pictures between cell phones, printers, and display devices. IrDA hardware was still less expensive and didn't share the same security problems encountered with wireless technologies such as Bluetooth. For example, some Pentax DSLRs (K-x, K-r) incorporated IrSimple for image transfer and gaming.[4]
When I got my first Indiglo watch, I realized the backlight had such fast rise/fall times (as compared to its incandescent predecessors) that it could be used to transmit data. I imagined watches with photocells, held face-to-face, flickering their backlights at each other to "synchronize watches" before a special-ops mission or something.
A few years later, Timex DataLink came out, indeed using a photocell to receive data, but not using the backlight to transmit it! And in all the years since, nobody ever took advantage of that.
But here we seem to be, with phones, a million times more powerful and a million times less power-efficient.
https://studios.disneyresearch.com/2012/12/03/an-led-to-led-...
https://la.disneyresearch.com/publication/connecting-network...
The real application for these "last meter" contactless ideas that use stalwart built-in transducers like mic+speaker or LED+camera, are to send short codes, such as shortened URLs. There's a whole bunch of fun to had using them for surreptitious advertising and public steganography.
I also think this tech is entirely impractical for one single reason: flashing visible lights can easily induce seizures.
With BLE available in pretty much every OS (and even in many browsers), I don't see the added value of quickly flashing a smartphone flash light.
if they built a protocol around it that handles error correction and noisy/intermittent links as well as nice apis for both sides, then i'd say they have something interesting.
With no feedback channel though, one can't characterize the channel though, so you need to have super large margins to be sure it's going to work.
Or does the amplitude of the led vary continuously? I was assuming PCM.
Yikes.
Double yikes.
triple!
Also that if you want to emit in the mhz range you need permissions and specialist equipment, but in the ~500 THz range you can just use a sub-dolar part and go ham with it without needing to be a ham.
The fact that THz EMR is completely unregulated and never discussed by the media is a sign that politicians and the scientific community are complicit in protecting industry at the expense of people's health.