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ADS1298 RREG read register problem

leo casal
Prodigy 90 points
Other Parts Discussed in Thread: ADS1298

Hi

I'm trying to read any register without success.

I'm able to initialize in rdatac mode and receive status register plus 8 channels. When I send sdatac, the dout goes to zero as expected. Then, I send an rreg opcode (eg read only ID control register) but receive no answer. 

Start, -Reset and -PWDN are tied to +V through a pull up resistor.

Is this a problem? I can't find in the datasheet anything saying the contrary.

Thanks in advance

Leonardo

  • 0
    Prodigy 90 points
    Anyone can help?
    thanks again
  • 0
    Prodigy 90 points

    Now I have connected Start pin to a microcontroller digital output, but still got no answer when issuing rreg.

    more info:

    at power up Drdy toggles at 250 Hz = 2.048 MHz / 8192

    Clk_sel is tied to +V

    Schematics:

    the SPI clk is configured at 77 KHz

    Screenshot with SPI clk and dout at  RDATAC.

    Status Word: First 2 bits are ON, next bits are OFF.

    If I short input to GND I measure 0 V.

  • 0 in reply to leo casal
    Prodigy 90 points

    I received ID Control Register for ADS1298, but I was sending RDATAC command! If I asked for more registers or different register it didnt work. I couldnt repeat this experiment. Any idea? Timing problem? initalization?

    dout (ID Control Register):

    din (RDATAC):

  • 0
    Prodigy 90 points
    Solved!
    The problem was SPI communication:
    The Master SPI Output (MOSI or DIN) must change on transition from idle to active clock state.
    I had it configured the other way
  • 0 in reply to leo casal
    Prodigy 215 points

    Hi leo,

    Actually I am also working with ADS1298 with C5515 EVM.

    I am currently able to receive data in SDATAC mode by RREG command and i am able to get data of ID register. But when I give the command to ADS1298 to go in RDATAC mode, I am just getting zeros. Even the Lead-Off status value to coming zero. Is there any way to get the data of Status register and all the 8 channels in SDATAC mode ?

  • 0 in reply to Ketan Shirokha
    Prodigy 215 points
    I got the answer. In SDATAC mode, when I issue RDATA command, I do get the 24-bit value of status register as 0xC00008 or (1100 0000 0000 0000 0000 0100)b. But I am not getting anything after that. Ideally one should get the data of each channel after the status register bits, but in my case, I am getting all zeros whether i give an input signal to channels or use internal test signal.