Could anybody explain me how many no of I2C devices can be connected in single bus.
How to calculate this.
What all parameters one should take care while designing.

Thanks in advance !!!

 

With I2C, device addressing will be the main limitation.
Bus speed is also a large factor.

Your other post regarding "overshoot and undershoot" -
What is important is that the logical thresholds are being met by the signals.
Overshoot and undershoot is not terribly relevant.

 

Thanks !!!

 

There is nothing to calculate. i2c is a standard, it is not a math/logic/life problem. You, the designer, adhere to the standard.
From wiki:
"The maximal number of nodes is limited by the address space and also by the total bus capacitance of 400 pF, which restricts practical communication distances to a few meters."
So the obvious restrictions is the address space and capacitance of the bus.
https://en.wikipedia.org/wiki/I²C#Reference_design

If you use the very basic i2c, that has 7 bit addresses for slaves and a master, you are looking at 2^7=128 devices total, 1 address for master and the rest of 127 addresses for slaves.

Then you start looking at the capacitance of the bus. You can probably do rough calculation.

Trobleshooting i2c 101 brought to you by AmpHour: https://theamphour.com/396-the-synergy-bus/
When having trouble with i2c, decrease pull up resistors.

 

https://www.nxp.com/docs/en/user-guide/UM10204.pdf

http://www.analog.com/media/en/technical-documentation/technical-articles/I2C-Cabling.pdf

https://electronics.stackexchange.com/questions/106265/maximum-i2c-bus-length

Regards, Dana.

 

There is nothing to calculate. i2c is a standard, it is not a math/logic/life problem. You, the designer, adhere to the standard.
From wiki:
"The maximal number of nodes is limited by the address space and also by the total bus capacitance of 400 pF, which restricts practical communication distances to a few meters."
So the obvious restrictions is the address space and capacitance of the bus.
https://en.wikipedia.org/wiki/I²C#Reference_design

If you use the very basic i2c, that has 7 bit addresses for slaves and a master, you are looking at 2^7=128 devices total, 1 address for master and the rest of 127 addresses for slaves.

Then you start looking at the capacitance of the bus. You can probably do rough calculation.

Trobleshooting i2c 101 brought to you by AmpHour: https://theamphour.com/396-the-synergy-bus/
When having trouble with i2c, decrease pull up resistors.

You really need to factor in the capacitance to the I2C devices. If you a 0pf on the bus and 127 devices, that would only allow 3 pf per device.

 

You really need to factor in the capacitance to the I2C devices. If you a 0pf on the bus and 127 devices, that would only allow 3 pf per device.

mishra does

 

Pardon me. I took "capacitance of the bus" too literally, meaning the bus only not counting loads.

 

Thank you all .