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Info about fanout of I2C bus

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ragabs

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Dear all,

i will use the serial port to interface with more than one of mc68hc908 controller and the distance between them will be 20 cm and the distance between the pc and the first controller will be about 100 cm
is this applicable?? and if yes how can i calculate the max number of controllers can i attatche them to serial port.
(i.e i ask about the fanout of the i2c bus )

thanx for help
 

alzomor

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Re: fanout of i2c bus

Hi

Max no of IC is limited by max bus capacitance of 400Pf

The fan out depends on and affect many factors

1-supply voltage
2-load capacitance of SCL and SDA which depends on distance , no of drriven ICs and track width and PCB material .
3-The speed of operation
4-Pull up resistor used


you can check the attached pdf
 

gidimiz

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Re: fanout of i2c bus

Hi,
A serial port in P2P ( Peer 2 Peer ) i.e. can talk to someone else and thats all.
Thinking about what you are trying to do, i can only suggest that you will use transistors to increase the line comunication thous you will be able to increase the distance to 100cm. you will also have to use low speed 100K data and not 400K.
To connect to the a serial port, you will have to put an MCU that will be the bridge between the serial port and your I2C.

Good luck.
 

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