Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Issues with interfacing two boards via I2C through cable

Status
Not open for further replies.

stanislavb

Advanced Member level 4
Joined
Jun 8, 2008
Messages
116
Helped
2
Reputation
4
Reaction score
2
Trophy points
1,298
Activity points
2,021
Hi,
The system include two boards connected each other with 1.5 - 2meter cable. The interface is I2C. Do I have to implement any impedance matching or standard pull resistor enough to get good signal shape?
Thank you
 

betwixt

Super Moderator
Staff member
Joined
Jul 4, 2009
Messages
14,859
Helped
4,854
Reputation
9,726
Reaction score
4,640
Trophy points
1,393
Location
Aberdyfi, West Wales, UK
Activity points
126,485
i2c cable length

The simple answer is yes. But, it depends on the I2C speed you are using and to some degree on the number of loads you are placing on the bus.

I2C does not have a minimum speed so you might be able to go slower if the cable length becomes a problem, that depends on how quickly you need to pass information around the system.

All I2C lines are open-collector (or open-drain) so you absolutely must use pull-up resistors, preferably at the slave end of the cable where they can help to dampen reflections. The value again depends on the bus speed. Lower value resistors will give sharper rising edges on the waveform, allowing higher speed to be used, but also need more current to be sunk by the driver to pull the signal lines down again. You should refer to the manufacturers data sheet for optimal values.

Try to use low capacitance screened cables if possible and remember that the ground potential between the two boards will appear as noise to the slave so keep it as low as possible.

Brian.
 

treitmey

Member level 1
Joined
Jan 22, 2008
Messages
38
Helped
4
Reputation
8
Reaction score
0
Trophy points
1,286
Activity points
1,510

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top