addressable I2C i/o chip recomendation?

Hi,

Can any one recommend an addressable I2C chip for driving an LED.

My requirements are: set the address (0-127), drive a single LED (on /off), low cost.

(I found this http://uk.farnell.com/jsp/displayProduct.jsp?sku=1564917&CMP=e-2072-00001000&gross_price=true, which I think would be suitable except I do not believe you can set the address)

cheers.

something like - http://www.sparkfun.com/products/8130 - ? datasheet - http://www.ti.com/lit/ds/symlink/pcf8575c.pdf -

Thanks for the suggestion but the datasheet says:

Address by Three Hardware Address Pins for Use of up to Eight Device

I ideally need up to 127 devices

you can add 8 of such chips, every one can control 16 lines (=16 leds)

8 x 16 = 128 , so you have one to spare.

Another option might be the centipede shield - http://macetech.com/store/index.php?main_page=product_info&products_id=23 - IIRC there can be two on the I2C bus (eight in fact but the library only support 2, but you may fix that ;)

2 x 64 = 128

hopes this helpes,

update: removed wrong info :blush:

Only 8 MCP23017 chips per bus, and each Centipede has 4 chips :slight_smile:

Use MAX6953. One chip. Control 140 LEDs. I2C interface. One current set resistor. http://datasheets.maxim-ic.com/en/ds/MAX6953.pdf

sorry I should of been more clear - I need around 120 individual units, after further research I guess maybe ATtiny45's might be the solution (creating BlinkM clones) although a little overkill for my application, as I only really need a single colour LED (possibly with with PWM).

Here is an alternative to BlinkM: http://www.seeedstudio.com/depot/grove-chainable-rgb-led-p-850.html?cPath=156_157 You can build it yourself, but it won't be much cheaper. Plus, I think you may get a discount when you buy 120 of them.

Do you have to be able to set an address for each LED? What if it's just a 2-wire communication where you shift data out to the entire string?

Take an RGB LED - $0.12 (1000 minimum) with a WS2801 - $0.16 (1 to 1000) 1x 0.1uF cap - $0.03 (100 - 499) 3x resistors - $0.02 (100 - 499) PCB - $0.72 (12 - I created my own through fab house)

And you end up with a pixel cost of $1.09 - multiply that by however many you want. Your Arduino just needs to provide a DATA and CLK source and you're done. You can either provide VCC/GND from the Arduino (3.3V up to 5.5V), or from an external supply.

Worth nothing: this is the exact same thing that many 5V addressable RGB strips are made of, except for the flexible and adhesive backing.

Actually, never mind. You indicated you're creating BlinkM clones, so these might not be sitting together in a long string.

thanks for the replies guys, yes the reason I'm thinking blinkM style devices is because my project requires a tree/branching style layout - and so chainable units would make for somne ugly wiring.

Then, if you're talking each unit being on its own, what does it matter if they're addressable or not? Just program each one and go to town with them.

As I need to be able to turn each unit of and on independently, from the control application.

So they will be wired together then, just not in a long continuous string, correct?

You could still do strings, just several of them going to individual branches. Each one would need 2 wires from the controller (NOT including VCC/GND). I get what you're saying though.