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Original question:

ADS1298: The first data read after start is alway "0"

ADS1298: ADS1298, the 27 bytes in the first frame are all 0 after the first falling edge of DRDY

Feng Xu
Intellectual 380 points
Part Number: ADS1298

Hi,

    My device uses ADS1298, and everything runs OK. The data collect is OK. I have used it for several years.

    Recently, I find that when the ADS1298 is started by writing the ADS_START (0x08) command, the first data read after start is "0" for all of the 8 channels.

    After that, everything runs OK forever.

    That only happens at the first frame I got after writing the ADS_START (0x08) command.

And the status word in the first frame after falling edge of DRDY pin is not "1100", what I get is "0000".

In fact, the 27 bytes in the first frame are all 0 after the first falling edge of DRDY.

Is that common for ADS1298?

    Thank you.

  • 0
    TI__Genius 11550 points

    Hi Feng,

    The status word in the ADS129x data readback will always start with 0b1100, as shown in Figure 61 in the datasheet. Does this happen if you issue a STOP command (0x0A) following by the START command? It may be helpful if you can capture the SPI waveform with a logic analyzer or oscilloscope.

    Thanks

    -TC