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ADS1292R 2 Electrodes ECG detection and CM noise cancellation (RLD) question

Yiwen Meng
Intellectual 500 points
Other Parts Discussed in Thread: ADS1292R, ADS1292

Hello,

I have implement the 2 electrode circuit for ADS1292R to detect ECG waveforms but the problem is that the signal is with common mode noise, so I refer to figure 47(page 50) on the datasheet of ADS1292R for applying RLD to cancelling CM noise. I just want to make sure my understanding is correct that I do not need add a third electrode for RDL input and the chip will automatically pick from the existed 2 electrodes, right? For the pin connection, I just need to connect RDLIN to RDLOUT and add 1Mohm resistance in parallel with 1.5nF capacitance between RDLOUT and RDLINV and set the the registers according the to figure, right?

Thanks,

Yiwen

  • 0
    TI__Mastermind 38745 points
    Yiwen,

    You hardware configuration is correct. The operation is actually not automatic. The register settings you make will configure the RLD for proper operation. I conveniently summarized them for you below:

    To enable the RLD amplifier, set bit 5 in the CONFIG2 register.
    To enable the electrode voltages to be fed to the RLD amplifier as inputs, set bits 2 and 3 in the RLD_SENS register. I assume the electrodes are connected to channel 2 since channel 1 is used for respiration on the ADS1292R.

    Regards,
    Brian Pisani
  • 0 in reply to Brian Pisani
    Intellectual 500 points

    Hi Brian,

    Thanks for your reply! I did set up the corresponding  registers and implement the whole hardware based on Figure 56 on the datasheet of ADS1292 and Figure 47 for Drive Right Leg, but I did not get the correct data, so I hope you could help me check my register setting is correct. Here is the code in Engergia:

    void setup_ADS1292 ()
    {
    send_command(SDATAC);
    write_byte(CONFIG1, 0x02);  //0b 0000 0010
    write_byte(CONFIG2, 0xA0); //0b 1010 0000
    write_byte(CH1SET, 0x40);  //0b 0100 0000
    write_byte(CH2SET, 0x07); //0b 0000 0111
    write_byte(RLD_SENS, 0x0C); //0b 0000 1100
    write_byte(RESP1, 0xF2); //0b 1111 0010
    write_byte(RESP2, 0x01); //0b 0000 0001
    write_byte(GPIO, 0x0C); //0b 0000 1100

    send_command(RDATAC);
    digitalWrite(PIN_START, HIGH);
    send_command(START);
    }

    Thanks,

    Yiwen

  • 0 in reply to Yiwen Meng
    TI__Mastermind 38745 points
    Yiwen,

    Have you been able to read the internally generated test signal? This is a good way to check your reading/writing pieces are correct. To enable the test signal, bit 1 and 0 of the CONFIG2 register must be set. Then mux the inputs to the test signal by setting the LSBs of the CH1SET and CH2SET registers to 0101. The output should be a 1 Hz square wave.

    Regards,
    Brian Pisani