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ADS1298 I want to read only one channel data over SPI

ramanjulu koneni39
Prodigy 70 points
Other Parts Discussed in Thread: ADS1298

Hello,

I am using ADS1298 in my device to measure evoked potentials. I have connected my electrodes to CH1_P, CH1_N and RLD

When I issue continuous read mode,  I am getting all channels data along with status bits

I need only one channel data, Please let me know, how to configure it

Thanks,

Ramanjulu

  • 0
    TI__Mastermind 38745 points
    Hello Ramanjulu,

    The data from the ADS1298 is shifted out on MISO in the following words:

    STATUS (24-bits) | CH1 (24-bits) | CH2 (24-bits) | CH3 (24-bits) | CH4 (24-bits) | CH5 (24-bits) | CH6 (24-bits) | CH7 (24-bits) | CH8 (24-bits)

    Total this is 216 bits. To get only channel 1, only toggle SCLK 48 times. That way the device will only shift out status and channel 1 data. You can then discard the status word if it is not of interest to you.

    Brian
  • 0 in reply to Brian Pisani
    Prodigy 70 points

    Thanks. It is working

    I have one more question:

    I have three electrodes: One for positive(IN1P), one for negative(IN1N) and other for reference (RLIN). Currently, I am using config register like below

    I want to measure evoked signal with respect to reference electrode. Please let me know, my configuration register values are correct or not?

    My register settings:

    //CONFIG1 0x0001
    0x0082,
    //CONFIG2
    0x0010,
    //CONFIG3
    0x00DC,

    //CH1SET (PGA gain = 6)

    0x0000,

  • 0 in reply to ramanjulu koneni39
    TI__Mastermind 38745 points
    Ramanjulu,

    There is no way to measure the signals with respect to the RLD with any internal routing. In the configuration you have, you will just measure the voltage between the positive and negative inputs. If instead you wanted to measure both the electrode voltages with respect to a single voltage, you' have to route that voltage to the negative channel inputs of 2 separate channels and route the respective electrodes to the positive inputs of the respective channels.

    Brian