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Why doesn't my SGTL5000 respond to I2C write commands from FRDM-K22F?

Question asked by Don Turner on Aug 9, 2016
Latest reply on Aug 10, 2016 by Michael Galda

I have a FRDM-K22F wired to a Teensy Audio Shield which is essentially an SGTL5000.

 

Whenever I attempt an I2C write I get a strange result - instead of getting an ACK I get a NACK. Checking with a logic analyser I can see that the I2C SDA line is pulled down only halfway. See the attached screenshot showing the analog output of Channel 2 which is I2C SDA - the problem point is marked at 1.902 V. What could be causing this strange behaviour?

 

Screen Shot 2016-08-09 at 22.22.16.png

I'm pretty sure it has to do with my K22F board configuration - perhaps I need to disable a pull up resistor somewhere?

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