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ADS1299 Evaluation !

Sankar Barua
Prodigy 50 points

Other Parts Discussed in Thread: ADS1299

Hi everyone,

I am evaluating ADS1299 using an ADS1299EEG-FE evaluation board. I am having trouble with acquiring a simple sine wave of 2 Hz of magnitude. I can observe a DISTORTED sine wave of magnitude of about 10uVpp.

if I increase the magnitude like 25uVpp, it seems it goes close to saturation and phase reversal happening a lot.

We measured the noise shorting all electrode together and found that the DC offset is about 1.4mV. The gain we are using is 24.

I just wonder if i am missing any  obvious setup issue here.

Thanks

Sankar

  • 0
    TI__Guru**** 182821 points

    Hi Sankar,

    Can you describe for us how you are connecting this signal source to the ADS1299 evaluation board?

  • 0 in reply to Tom Hendrick
    Prodigy 50 points

    Hi Tom,

    I am sorry for late reply. I have been trying different configurations. Here is the way  we connect signal to ADS board:

    I have 4 electrodes, which are Channel 1 positive (Ch1P) Channel 2  Positive (Ch2P) Reference (Ref)  and Ground (GND),  to connect to ADS. The Ch1P is connected to Pin 36 of J6; Ch2P connected to Pin 32 of J6; Ref connected to both Pin 34 and 30;  and GND connected to TP 11.

    We have a patient simulator capable of producing uV of differential/Referential signals. We drive the electrode with differential signal across Ref and Ch1 for Channel 1 and Ref and Ch2 for channel 2. Patient Simulator output ground is connected to GND electrode.

    Here is the register values i used to config the ADS:

                cADSINIT[0] = %10010100 //CONFIG1: baud rate 1000 SPS; DAISY_EN
                cADSINIT[1] = %11000000 //CONFIG2:
                cADSINIT[2] = %11100000 //CONFIG3:
                cADSINIT[3] = %00000000 //LOFF:
                cADSINIT[4] = %01010000 //CH1SET: Normal Operation; Gain = 12
                cADSINIT[5] = %01010000 //CH2SET: Normal Operation; Gain = 12
                cADSINIT[6] = %10000000 //CH3SET: Power down
                cADSINIT[7] = %10000000 //CH4SET: Power down
                cADSINIT[8] = %10000000 //CH5SET: Power down
                cADSINIT[9] = %10000000 //CH6SET: Power down
                cADSINIT[10] = %10000000 //CH7SET: Power down
                cADSINIT[11] = %10000000 //CH8SET: Power down
                cADSINIT[12] = %00000000 //BIAS_SENSP:
                cADSINIT[13] = %00000000 //BIAS_SENSN:
                cADSINIT[14] = %00000000 //LOFF_SENSP:
                cADSINIT[15] = %00000000 //LOFF_SENSN:
                cADSINIT[16] = %00000000 //LOFF_FLIP

                cADSINIT[0] = %00000000 //GPIO
                cADSINIT[1] = %00000000 //MISC1
                cADSINIT[2] = %00000000 //MISC2
                cADSINIT[3] = %00000000 //CONFIG4

    Now i am being able to acquire test signal of 1 Hz and 3.75mVpp by changing configuration in internal test signal mode. All gain setting  work but Gain 24. At Gain 24, the output does not correlate with input and Gain setting.

    Now  i am trying to input a pure sine wave and see the output. So far no luck. The frequency seems right but waveform are  completely DISTORTED.

    Any help will be appreciated.

    Thanks

    Sankar

  • 0 in reply to Sankar Barua
    Prodigy 50 points

    hi i want to buy ads 1299 for my project . do i have to buy ic or i should go with ads 1299 fe kit please help me out. the output signal from this kit is given to omap 3530. this is what i have in my mind please help me where should i start first

  • 0 in reply to pavan shet
    Intellectual 455 points

    hi EVERYBODY!!!

    I wanna to drive the ADS1299 with the pic18f452 across SPI comunication. but reading the data sheet of the ADC. it makes mention of some control registers.

    I don't have any idea how to write these registers.

    I hope somebody can help me!!!

    best regards!!!