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I2C Commmunication depends on OSS_Sel of DS90UB914A?

Lars Tischendorf
Prodigy 110 points

I want to remote configure an DS90UB913A in an camera over DS90UB914A.

The ICs are connected over Coax.

Now, I observed, that the remote communication is not possible, if the OSS_Sel Pin is high. If OSS_Sel is high, I don't get any ACK.

The I2C communication with DS90UB914 directly works everytime. If OSS_Sel is low, I get an ACK from DS90UB913A.

I don't understand this correlation.

I have read out the SER ID register in 914. There is the correct ID (0xB0). But in DES ID Register of 913 (If I read direct over I2C), there is a Zero, if OSS_Sel of 914 is high.

  • 0
    TI__Expert 5210 points
    Hello Lars,

    I have a feeling that upon powering-up the system you are leaving one of the configuration pins floating (OSS_SEL, OEN, BISTEN, RES, or SEL).

    Are you ONLY toggling OSS_SEL when you try to make the ACK issue reappear? Also, have you probed the OSS_SEL pin to ensure that it is HIGH or LOW depending upon your configuration?

    Please also check register 0x0C[0] when the issue reappears. This will well us back channel LINK detect status and whether there is even back channel communication when you are sending/receiving I2C data in regards to the 913A device.

    -Sean
  • 0 in reply to Sean Thornton1
    Prodigy 110 points

    All this Signals are Pullup/Pulldown at powering up.

    I think, I have an emi problem.