i2c connection

Thread Starter

kppp

Joined Apr 23, 2008
14
hell everyone;
i want to know that how many devices can we interface on i2c.
and this is dependent upon which factors??
thank u all.:)
 

Caveman

Joined Apr 15, 2008
471
Even though there are 128 possibilities for addresses, the actual limitation is typically due to the loading each device adds to the line. This is due to the capacitance each gate adds. So, the answer is, it depends. It depends on the devices' electrical properties.
 

Papabravo

Joined Feb 24, 2006
13,972
Even though there are 128 possibilities for addresses, the actual limitation is typically due to the loading each device adds to the line. This is due to the capacitance each gate adds. So, the answer is, it depends. It depends on the devices' electrical properties.
The length and type of cable will also have an effect on the properties of the signal. You can get an idea of what is possible by looking at the transmitter characteristics in terms of "what is a 1" and "what is a 0". then look at the receiver characteristics to see what it would take for a "0" to change to a "1" and vice versa.

You also need to look at how the nodes are powered and weather their grounds are at different levels. It's complicated stuff, and guys get paid big bucks for figuring this kind of stuff out.
 

Caveman

Joined Apr 15, 2008
471
You should remember that I2C means Inter-IC bus. It is not designed to be used for cabling between boards. CAN is a more appropriate bus for that application.
 

Papabravo

Joined Feb 24, 2006
13,972
That was the original intention, but there was a variation called Access Bus that envisioned going longer distances. I guess if you're thinking about 128 nodes you must be thinking more than a board.

CAN was not originally envisioned by Bosch as more than an on-vehicle network, but look at what it evolved into.
 
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