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Original question:

SM72442: Inductor size in SM3320 reference design

SM72442: Communication with SM72442 and Raspberry pi

Noman Bashir6
Prodigy 130 points
Part Number: SM72442

Hi Everyone!

I am trying to communicate between my Raspberry Pi Zero W and SM72442. 

I have made the connections and setup according to this tutorial: https://learn.sparkfun.com/tutorials/raspberry-pi-spi-and-i2c-tutorial

Additionally, as Raspberry Pi I2C works at 3.3V and SM72442 works at 5V, I have used this logic level converter: https://www.sparkfun.com/products/12009

However, as I run the i2cdetect -y 1 command, I do not see my device on the connected list. Can you please tell me what could be happening? 

  • 0
    TI__Guru* 78200 points

    0636.SM72445_USB2ANY_AN_melo_2018Mar.pdf

    Please refer to the attached guide for I2C programming.  You may contact the vendor Sparkfun for support.

  • 0 in reply to Youhao Xi
    Prodigy 130 points
    I am really sorry, but I am unable to understand how this solves my problem. This platform just provides a way to control an EVM device from PC and it has a dedicated software for it. I am looking to control the device from Raspberry Pi (using Python). Also, Sparkfun device is just a logical level converter and is working fine. Can you please guide me towards any troubleshooting for the basic circuit for SM72442? I have configured my circuit according to this application note: www.ti.com/.../sm72442.pdf. Is there any way to check if my SM72442 is up and responding or not?
  • 0 in reply to Noman Bashir6
    Prodigy 130 points
    Hi , can you please give you opinion on should the logic level conversion be used? Or atleast how to check if my SM72442 IC is working or not?
  • 0 in reply to Noman Bashir6
    TI__Guru* 78200 points
    I am going to ask one of my colleagues to see if any advice can be provided.
  • 0 in reply to Youhao Xi
    TI__Guru* 78200 points
    Here is the advice that I got from my colleague:

    According to the datasheet, it is OK to use 3.3V to I2C, so the level shift circuit is not required.

    -----Datasheet Quote-----
    SDA and SCL OPEN DRAIN OUTPUT
    SCL and SDA output is an open-drain output and does not have internal pull-ups. A “high” level will not be
    observed on this pin until pull-up current is provided by some external source, typically a pull-up resistor. Choice
    of resistor value depends on many system factors; load capacitance, trace length, etc. A typical value of pull- up
    resistor for SM72442 ranges from 2 kΩ to 10 kΩ. For more information, refer to the I2C Bus specification for
    selecting the pull-up resistor value . The SCL and SDA outputs can operate while being pulled up to 5V and
    3.3V.
    -----The End of Quote -----

    The customer should follow page 13, 14 to debug the circuit, measure the waveform in SCL and SDA to check if they meet the datasheet requirements.

    Hope this helps.

    Thanks.
  • 0 in reply to Youhao Xi
    Prodigy 130 points

    Thanks a lot for the response. I will do these steps and get back.