1 Reply Latest reply on Nov 19, 2020 5:30 AM by ShifangZ_26

    Can't read I2C from CYPD3177


      I am trying to use I2C to read the CYPD3177.  I am using the EZ-PD BCR Host Processor Interface Specification Doc # 002-26784.  In this document, it states to read the BCR, you need the following I2C transaction:



      The REG ADDR shown above is a 16-bit address of the register you would like to read according to the document.


      I am trying to read address 0x100D, which is the bus voltage register:


      My I2C transaction is shown below:


      As you can see the device address is properly ACK'ed, then the 16-bit address is properly ACK'ed, but then I do a restart(send the start sequence again), and do a read transaction to the same device address, but here the device NACKs.  What is the reason for the NACK?


      Here is a close up view of the restart and NACK:



      Also in the document listed above it states, the BCR device can operate in one of two modes, standalone and HPI mode, and certain writeable registers are only available in HPI mode.  Looking at the document and the datasheet it doesn't state how to get the device into HPI mode to perform the write operations.


      Thank you.