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Author Topic: EMI (Radiated) caused by I2C. Need help.  (Read 22287 times)

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Offline guscrownTopic starter

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Re: EMI (Radiated) caused by I2C. Need help.
« Reply #25 on: March 31, 2011, 11:28:40 pm »
Quote from: scrat on March 31, 2011, 10:06:40 pm
You've still to try with common mode chokes, haven't you?

PCB Macro will not allow common mode choke coils unfortunately. PCB relayout at this stage is almost impossible I think.
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Offline scrat

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Re: EMI (Radiated) caused by I2C. Need help.
« Reply #26 on: March 31, 2011, 11:38:09 pm »
Quote from: guscrown on March 31, 2011, 11:28:40 pm
Quote from: scrat on March 31, 2011, 10:06:40 pm
You've still to try with common mode chokes, haven't you?

PCB Macro will not allow common mode choke coils unfortunately. PCB relayout at this stage is almost impossible I think.

It's one of the first options you had, by applying cores on the cables. Since the other solutions didn't work (but, of course, try with capacitive loading), it will be helpful to know if chokes work.
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Offline guscrownTopic starter

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Re: EMI (Radiated) caused by I2C. Need help.
« Reply #27 on: April 01, 2011, 02:24:08 am »
I think I have found the culprit. One of the lines in my cable is carrying a control line to powering an LED (typical green LED that indicates the equipment is ON). I disconnected this line and voila, noise gone.

This is a typical LED circuit, anode is connected to 3.3V, and I control the LED state via the cathode. Something ODD is going on. 
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