Dear All,

I have a circuit based on the old DSP chip from analogue devices ADAU1701. It communicates over I2C with the address 0x34. Now, if I use an arduino or ESP32 I get an ACK from the board, but ONLY if I power the ADAU1701 board via the USB port on my macbook pro. If I use a LiPo battery pack (designed for charging phones and tablets) or a usb phone charging plug (straight into the mains) I get an I2C timeout!?!?

I have used the typical application section from the datasheet to design the circuit, including voltage regulators, and all the decoupling and bulk caps.
Any ideas of what is going on? How can I make the circuit more robust so that it can handle different sources of power (which should all be 5V and perfectly adequate supplies)?

Many thanks in advance,

Tim

 

I would use a scope single shot qualified trigger by pulse width and
look at pins on interface and ESP32/Arduino to see if you are getting
transient coupling into a pin. Inputs or outputs. Also just look at I2C
interface for overshoot/undershoot. And to see if buss decodes properly.

What value pullups are you using ? If they are too high could be subject
to coupling, too low not meeting logic level specs for interface.

http://www.ti.com/lit/an/slva689/slva689.pdf


Regards, Dana.

 

Everyone can’t read a .sch file. Please post a clear screenshot or image of the schematic. Make sure it’s large enough to be able to read.

Is the ground of your circuit connected to ground of the microprocessor!

 

The grounds weren't connected!!! Of course!

Thanks djfantasti for the solution (next time I'll upload a screenshot), and thanks Dana for showing me that i2C busses can be quite complicated and need designing carefully.

Many thanks,

Tim