jamesh
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
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Re: Visible Light Communication using RasPi and a Smartphone

Thu Jun 04, 2015 3:18 pm

Two Raspi's, one with a camera, one with a Unicorn HAT. Run the Unicorn like a QR code, take images uses the camera and decode the image. If you are feeling particularly flash, you could also use the colour of the LED's to improve the bitrate, even just using R,G,B,W gives a 8x increase in speed.

Cost is cheaper than a Pi plus a Smartphone....
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procount
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Re: Visible Light Communication using RasPi and a Smartphone

Thu Jun 04, 2015 3:34 pm

This looks like it does the same thing:
http://shop.taxan.co.jp/id-rxs.html
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BMS Doug
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Re: Visible Light Communication using RasPi and a Smartphone

Thu Jun 04, 2015 3:58 pm

jamesh wrote:Two Raspi's, one with a camera, one with a Unicorn HAT. Run the Unicorn like a QR code, take images uses the camera and decode the image. If you are feeling particularly flash, you could also use the colour of the LED's to improve the bitrate, even just using R,G,B,W gives a 8x increase in speed.

Cost is cheaper than a Pi plus a Smartphone....
Perhaps the OP will consider your suggestion, he seems to have discounted my similar idea.
Kohime wrote:regarding the 8x8 matrix or the 7segment display, I have not really considered it. The solution I have been working on is really about sending binary code by blinking a led.
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boyoh
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Re: Visible Light Communication using RasPi and a Smartphone

Thu Jun 04, 2015 10:33 pm

This is only a suggestion for your VLC project
Use a ultra bright LED focused through
length of Fiber Optic to the camera lens,
Might work might not. This would only be
the hardware side of the project.
BoyOh ( Selby, North Yorkshire.UK)
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Kohime
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Re: Visible Light Communication using RasPi and a Smartphone

Wed Jun 17, 2015 9:50 am

Hello everyone and thank you for your help.

To continue this project I would like to create the cheapest possible device to blink a LED. Is it possible to create suck a device powered through the jack port of a phone ? I have found the project HiJack (university of michigan) that does something like that, but their system design seemed a lot more complex than what I am trying to do, a "simple" led blink peripheral.

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DougieLawson
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Re: Visible Light Communication using RasPi and a Smartphone

Wed Jun 17, 2015 9:56 am

Cheapest and simplest LED blinker is a 555 timer.
https://www.google.co.uk/search?q=555+led+flasher
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Kohime
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Re: Visible Light Communication using RasPi and a Smartphone

Wed Jun 17, 2015 11:28 am

Thanks ! Do you think the Jack port of a phone could power it ?

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procount
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Re: Visible Light Communication using RasPi and a Smartphone

Wed Jun 17, 2015 12:05 pm

From your previous posts, I thought you were using the smart phone as a receiver and the RPi was doing the transmitting from an LED.
Have you turned this around now or are you doing bi-directional communication?

Transmitting light from the headphone socket will require more power than simply receiving the data. The Hijack project harvests 7.4mW from the headphone socket using a 22KHz tone (AC-DC conversion, I guess). This might be enough to make an LED glow, but you I wouldn't think you'd be able to transmit over any great distance.
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toxibunny
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Re: Visible Light Communication using RasPi and a Smartphone

Wed Jun 17, 2015 5:10 pm

add a transistor and a couple of button cells then. no?

I don't see any reason the 555 is needed, personally.
note: I may or may not know what I'm talking about...

drgeoff
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Re: Visible Light Communication using RasPi and a Smartphone

Wed Jun 17, 2015 6:07 pm

toxibunny wrote:I don't see any reason the 555 is needed, personally.
That was just one of Dougie's irrelevant replies after he fell back into his bad habit of glancing at posts instead of reading them.

boyoh
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Re: Visible Light Communication using RasPi and a Smartphone

Thu Jun 18, 2015 8:57 pm

I'm getting a bit confused as what you are trying to do
Your first post was to transmitted a visible light signal
from a Pi to a Smart Phone camera.
Your post changed to flashing a LED from the phone.
I suggest you sort one problem out , before creating
other problems.

Am I correct that you want the Pi to transmitte a coded
signal ,using a pulsing LED to a Smart Phone camera
lens, to be de-coded by the Smart Phone
BoyOh ( Selby, North Yorkshire.UK)
Some Times Right Some Times Wrong

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