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I2C Interface between TM320DM368 and TCA9517

Chee Wooi Cheok
Prodigy 190 points
Other Parts Discussed in Thread: TCA9517

TCA9517 data sheet (page 2/21) stated that

"Because of the buffered low voltage from the B side, the TCA9517 cannot be connected B side to B side and to ensure clock-stretching support the B side should not be connected to a device with rise time accelerators."

 

Question 1

Please refer to the attached file on the I2C interface. 

Is it ok to use TCA9517 as level shifter to interface with only 1 of the 3 devices, and the other 2 devices are directly interfaced to DM368 (as I2C master)?

(All the 3 devices can support fast mode up to 400kbps)

 

 

Question 2

From the link below:

http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/100/p/227663/800566.aspx

Renjith is saying that "I don't think it's possible to do I2C clock stretching in DM36x."

 

In this case, can DM368 still work with TCA9517 without clock stretching support on the B side?

Or is there a need of clock stretching implementation for SCL up to 400 kHz max?

Kindly enlighten

Regards

 

  • 0
    TI__Intellectual 2020 points

    Hi Chee,

    Is it ok to use TCA9517 as level shifter to interface with only 1 of the 3 devices, and the other 2 devices are directly interfaced to DM368 (as I2C master)? Yes this is a valid implementation 

    In this case, can DM368 still work with TCA9517 without clock stretching support on the B side? The TCA9517 does not require clock stretching support it just will support clock stretching if it exists in the system. What you do need to ensure is that your slaves (device 1-3) do not attempt to clock stretch if your master does not support it.

    Regards,
    Chris Kraft 

  • 0 in reply to Chris Kraft
    Prodigy 190 points

    Dear Chris,

    Thanks for replying.

    Unfortunately, it seems like one of the 3 devices (and it's the device connected to DM368 through TCA9517) is stretching the clock.    

    Based on your comment "What you do need to ensure is that your slaves (device 1-3) do not attempt to clock stretch if your master does not support it." does it mean that interface between DM368 (does not support clock stretching) and the device (which is stretching the clock) is not possible even they are connected through TCA9517?

    Could you please advise any TI devices that will act as a medium to enable the I2C interface between DM368 & a device that is stretching the I2C clock?

    Thanks & regards