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SN65DP159: not giving ACK, not detected in I2C probe

Jayakrishnan Menon
Prodigy 70 points
Part Number: SN65DP159

Hi 

We are working on a custom board based on the ZynqMP SoC.  Using the SN65DP159 retimer IC on the HDMI TX path.  The DP159 is connected to the i2c bus lines and controlled from the AXI-IIC soft IP.  We were able to detect the same chip on the development kit we were using, but when it comes to custom board we are facing an issue in detecting the chip.

Checked the relevant voltage lines, seem to be fine. Hope it should be working in the i2c-mode as the I2C_EN PIN is HIGH.

Tried probing the SCL SDA lines, and observed we are not receiving an ACK from the DP159. There is another EEPROM chip on the same bus to which we were able to do transactions.

But the DP159 is not detected even in i2cdetect on the same bus. 

Please provide any suggestions on the possible debug to root out the issue. 

Thanks & Regards,

Jayakrishnan 

  • 0
    TI__Guru**** 177446 points

    Jayakrishnan 

    Can I please take a look at your schematic?

    1. Please make sure the DP159 power requirement is met. The DP159 has an internal pull-up resistor on the OE pin, so you only need an external pullup capacitor, we typically recommend a 0.22uF cap on the OE pin

    2. I2C address, what I2C address does DP159 set to?

    3. I2C SDA and SCL pullup resistor, what is the value of the pullup resistor on SCL and SDA?

    4 I2C bus contention, can you remove the EEPROM from the bus and see if you are able to communicate to the DP159?

    Thanks
    David

  • 0 in reply to David (ASIC) Liu
    Prodigy 70 points

    Hi David, 

    Thanks for the quick response. 

    I can attach the schematic snippet with DP159 & EEPROM coming in the same bus. Please find the attached image.

    1. Please make sure the DP159 power requirement is met. The DP159 has an internal pull-up resistor on the OE pin, so you only need an external pullup capacitor, we typically recommend a 0.22uF cap on the OE pin

     We have checked the voltages on PINs 42 - OE( 3.3v), 10 (2.58v),21 (400mV) ,22 (20mV) ,27(20mV), but there is no 0.22uF as per the schematic of custom as well as the reference board. The OE is being routed to the respective SOM net basically.

    2. I2C address, what I2C address does DP159 set to?

        The address assigned to the DP159 is 0xBC .

         EEPROM ( M24C08-WDW6TP) is 0xA0 ( having 4 possible addresses with A8,A9 address pins).

        The current I2Cdetect dump gives the address 0x50,0x51,0x52,0x53. ( right shifted addresses of eeprom). We have checked the read/write to eeprom which is fine.

    3.  I2C SDA and SCL pullup resistor, what is the value of the pullup resistor on SCL and SDA?

    The pull-up resistors on SDA and SCL are both 2.2K, pulled upto 3.3v.

    4. I2C bus contention, can you remove the EEPROM from the bus and see if you are able to communicate to the DP159?

    we shall try this & see for any effect.

  • 0 in reply to Jayakrishnan Menon
    TI__Guru**** 177446 points

    Jayakrishnan 

    The last bit is the W/R bit, only the first 7-bit is the I2C address.

    For 0xBC, can you write to I2C address of 0x5E?

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    Prodigy 70 points

    THe i2cdetect shows only the eeprom addresses and not the dp159, so even when we try to access, not getting the ACK. 

    The same address is assigned on the reference board, where we read the 0x5e that is the address that the i2cdetect shows ( 7 bit address without the W/R bit in 0xBC that is 5E).

  • 0 in reply to Jayakrishnan Menon
    TI__Guru**** 177446 points

    Jayakrishnan 

    Looking at the schematic, the SCL_SNK and SDA_SNK need to be pulled to 5V, but this is a separate issue from the DP159 not seen on the I2C bus.

    Are you actively driving the OE pin? Is it possible to just have the 0.22uF pulldown cap on the OE pin? I want to make sure the power up sequence is not violated. The OE must go high after the VCC/VDD is high (min 100us).

    Thanks

    David