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Connection different I2C devices to the same bus.

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flote21

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Hello folks,

I am wondering about how many different I2C devices can I connect to the same I2C Bus?? Is there any limitation? Of course, considering that all the devices connected have different addresses.

Thanks in advance!
 

Hi,

It´s all given in the I2C specifications. Please read through them.

It´s mainly limited by:
* addresses
* capacitive load by the device inputs
* drive strength
* pull up resistor
* traces / wiring
* bus (clock) speed
...

Klaus
 

I2C bus have addresses are either 7 bits or 10 bits.
Ideal case:
For 7 bit: you can have up to 128 devices on the I2C bus, since a 7bit number can be from 0 to 127. Similarly, for 10 bits, 1024 devices.

Practical case:
The speed of operation and cable capacitance will affect the no of devices (to work properly) in the bus.

For 100kHz speed (Typical speed), the maximum supported cable capacitance is 400 pF. For fast mode, capacitance should be less than 200pF.

If your wire is 30pF/30cm and you have another 50pF of stray and input capacitance, you're limited to 1.5m of cable length (Theoretically!) for 100Khz mode.
 

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