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PCA9956 I2C clock frequency

Question asked by Dare Dare on Oct 8, 2018
Latest reply on Oct 8, 2018 by Dare Dare

Hello, 

I have built a LED controller for 24 LEDs and it works perfectly if I use I2C clock rate of 100kHz. If I try to use 400kHz, I cant see the LEDs powering up, the device doesn't work. I have tried to monitor I2C lines on the scope, they seem OK, my device do not add too much capacitance to the I2C bus.  I have tried it with two different microcontrollers, so I'd rule out slew rate control of the I2C pins or bad libraries...

 

My question is: do I need to follow some specific I2C initialization (such as sending 0001xxx I2C code) to work with 400kHz, or the problem lies elsewhere ?

Thanks in advance

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