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ADS131E08: ADS131E08IPAG

Bilal Canturk
Prodigy 20 points
Part Number: ADS131E08


Hi,

I have a problem about SPI interface, spesifically DOUT line. I was able to read and write registers of ADS131e08  but when i put the device into continious read mode i can't get the data at DOUT line into my MCU through MISO line. As you can see in Figure-2, when i don't connect DOUT to MISO and observe the DOUT line , it seems DOUT transmits data. When i connect  DOUT and MISO ADS131e08 stops. After connection i send a reset and put device into continious read mode and observe Figure-3. DRDY works but there is no data on DOUT line.

I applied power-up sequence in datasheet Figure:53.

Analog Supply:5V Digital Supply:3V (Unipolar Supply)

CS is tied low after reset pulse. (I didn't selectively Pulled Low Before sending commands or reading data)

SPI Baud Rate : 1.5 MHz 

MCU SPI mode is Full-fuplex master. (cpol=0, cpha=1)

MCU MISO pin is "alternate function push pull mode".

MCU GND is connected DGND.

You can see schematic in Figure-1 (Designed according to ADS131e08 user guide)

Any help or offer or information about DOUT line will be appreciated. 

Thank you. 

Figure-1 : Schematic of ADS131E08

Figure-2 : BEFORE  (ADS131E08) DOUT--------> (MCU) MISO  connection

 BUS (Green) : DOUT

Digital 0 (white) : DRDY

Digital 1 (orange) : SCLK

 

Figure-3 : AFTER  (ADS131E08) DOUT--------> (MCU) MISO  connection

 BUS (Green) : DOUT

Digital 0 (white) : DRDY

Digital 1 (orange) : SCLK

  • 0
    Prodigy 20 points
    As an additional information In Figure-3 when i remove DOUT- MISO connection i can observe same situation in Figure-2. It means DOUT can pull itself high when no connection, but can't pull itself high with connection.
  • 0 in reply to Bilal Canturk
    TI__Guru 67206 points

    Hello Bilal,

    Thanks for your question.

    The fact that DOUT is functioning normally upon removing the DOUT->MISO connection indicates that the ADC is functioning properly. This might be an issue with your MCU MISO pin configuration instead. Does "alternate function push pull mode" mean that the MCU MISO pin is always configured as an input? Make sure that the MCU MISO pin is not accidentally driving the DOUT pin on the ADS131E08.

    Best Regards,