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Length of I2C bus
Someone on here described their I2C bus as "long" when it was only 4 feet. I'm planning on using some MaxM LED units in a display that requires several meters of cable between the Arduino and the units. Will this work okay?
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Inappropriate?Hi Adam,
It's true that I2C is designed as a "chip-to-chip" protocol, not something going over cables. But I've had I2C cables as long as 20 feet with no problems. You need 4.7k pull-up resistors on the two data lines. When people want longer runs, they use I2C line driver chips. We're currently evaluating a few and when we have some recommendations we'll post them here.
Since you're driving MaxMs, I suspect the larger problem will be getting adequate power to them. If you're using the MaxMs in the Master+Blaster configuration, each MaxM draws 1/4 Amp and most ribbon cabling can't do more than one Amp. You might need to run separate power cables to each MaxM.
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Inappropriate?hey i'm going to have this same issue. I bought a master and 2 blasters for testing though i want to eventually drive up to 8 blasters when im done. I thought it could just daisy chain them like in the example in the PDFs and hang them from the ceiling spaced 5 feet apart.
I’m sad
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This answers the question
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link to 12c extender:
http://www.picbasic.co.uk/forum/showt... -
Inappropriate?Thanks for the response todbot.
I'm not so worried about the power consumption; I'll have individual power sources for each MaxM group and some heavy duty cabling to handle the current draw.
In terms of the I2C bus, would a simpler approach be to simply increase the distance between the MaxM Master board and the MaxM Blaster board, while keeping the I2C cable extremely short?
i.e. if I have a 50cm cable between the Arduino and all MaxM Master boards and ten metre+ extension between the Master and Blaster boards.
Let me know your thoughts!
(Great product BTW!)
I’m excited
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This answers the question
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I will have a I2c -> twisted pair converter available soon at FunGizmos.com that will allow you to connect two I2C busses with up to around 300M of twisted pair cable. With two of these you could separate the Arduino from your array of BlinkM's by quite a distance.
Will -
Thanks Will. Be sure to post here when it's available. I hope you ship internationally (Australia)!
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Inappropriate?I have a similar issue running 25 blinkMs along a 25 foot I2c bus. Its not working very well and I'd like to use a fast clock speed, can anyone recommend a good I2C line driver chip to make this work?
Thanks,
Aaron
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