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ADS1299 EVM board, AGND is high

qi wang
Intellectual 480 points
Other Parts Discussed in Thread: ADS1299

Hi,

I am using tiva C board to acquire data from ads1299, and the connection is like:

ADS1299 mother board ----->(used all 10 pins of J4 connector for power supply, etc)-----> ADS1299 daughter board --> (J3 connector for SPI) --> TIVA C board.

The issue is that, tiva C can not control the SPI pins on the daughter boad via the GPIO. One obvious problem is the (~cs) SPI select pin (pin 1 of J3 of the daughter board) is always high, even driven by a low level signal from GPIO pin on tiva C board. So the SPI can not start to wok.

The question is why ‘the (~cs) SPI select pin (pin 1 of J3 of the daughter board)’ is always high, i.e. non-controllable? I tried to connect the AGND of the daughter board (pin4 of J3) to GND pin of the tiva C board, but the LEDs on the mother board are off (I think the mother board stopped supplying power because of some issue).  Is it 

Thank you!

Qi

  • 0
    TI__Mastermind 38745 points
    Hey Qi,

    TI will not provide support for radical changes to the EVM board, but it's possible that another community member helps you with this issue. What I can say from what you've stated about the issue is that there should not be an electrical problem tying the grounds of the daughter board and the Tiva Launchpad together, as long as both are powered independently. The grounds must be at the same potential for SPI to work, so I'd work out that issue first. Get a multimeter and probe some of the voltages to see which supplies are good and which are still bad and that will likely give you some insight to the problem. I apologize that we will not be able to support you directly on this.

    Regards,
    Brian Pisani
  • 0 in reply to Brian Pisani
    Intellectual 480 points
    Thank you, Brian!