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ads1293-spi

Nazrul Khan
Prodigy 230 points

Other Parts Discussed in Thread: ADS1293

Hello,

I am using ADS1293 in my project to collect ECG signal. The microcontroller(PIC) is communicating with the ADS1293 through a 3 pin(SCLK, SDO, SDI) SPI interface. I am also using an I/O pin as CS. Through the SPI, I am writing the control registers within the ADS1293. But looks like these registers are not getting written. Through oscilloscope, I can see the control words are getting out of the microcontroller but whenever I read the same registers from the ADS1293, they are not same. I am using 4MHZ as the SCLK frequency. Can you please, tell me what is wrong here. Regards.

Nazrul

  • 0
    TI__Guru 50036 points
    Hi Nazrul,

    I am moving your post to the correct forum.
  • 0 in reply to Praveen Aroul
    TI__Genius 16890 points
    Hi Nazrul,

    Please check your CS, SCLK, SDI and SDO signals with an oscilloscope and make sure that the timing between the signal are within the timing specs listed in sections 7.6 and 7.7 and shown in Figures 1, 2 and 29.
    When you are writing make sure that it is not converting. Bit 0 of register has to be 0 in order to write to registers.
    Make sure that the VDDIO is the correct value and that the SPI signal maximum is VDDIO. The VDDIO should be set as shown in section 7.3.

    Mike
  • 0 in reply to Michael Stout
    Prodigy 230 points
    Hi Mike,
    Thanks for the reply. I have few queries on your reply.
    1. As you said, " when writing, make sure that it is not converting". What does it mean and how it happens? How to prevent that?
    2. Is it bit0 or bit7 has to be 0 in order to write that register?
    3. At what SCLK frequency, this AFE works best.
    Best regards.
    Nazrul
  • 0 in reply to Nazrul Khan
    TI__Genius 16890 points

    Hi Nazrul,

    1.  Not converting means that the ADC is not converting the analog signal to digital codes.  This is controlled by the START_CON bit (bit 0) in the CONFIG register (0x00).  Setting the START_CON bit to 0 will disable the ADCs.  When START_CON is set to 1 the ADCs will convert (as long as everything else is set up correctly).  Also when START_CON = 1 the registers 0x11, 0x12, 0x13 and 0x21 - 0x29 are locked and cannot be written to.

    2.  The START_CON bit is bit 0.

    3.  The SCLK can be up to 20MHz. 


    Mike