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ADS1299: No DRDY pulses

May
Genius 9880 points
Part Number: ADS1299
Other Parts Discussed in Thread: ADS1294

Hi Team,

Good day, we received query from customer and we would like to seek for your expertise regarding this. For me to not miss any information, I will copy the query below.

"
1. I am working on a board with ADS1299 chips and I am using the SPI Bus which is shared with an SD card. When I try to write to SD card, I don't see any DRDY pulses?

(please see attached waveform)

2.In ADS1294 / 6 / 8 datasheet: section 9.4.1.2 DRDY pin, it says that SCLK has to be gated externally, is it true for ADS1299 as well? I did not find any similar suggestion for ADS1299 chips (in datasheet)

"

Thank you and looking forward for your kind response.

Regards,

Maynard.

  • 0
    TI__Mastermind 49906 points

    Hello Maynard,

    The dependency of SCLK on DRDY is valid for ADS1299 as well i.e. regardless of the status of the CS signal, a rising edge on SCLK pulls DRDY high. and hence the recommendation to gate SCLK with CS hold true for ADS1299 as well.

    The DRDY pulses are probably still coming in but with the continuous SCLK pulses, the logic analyzer tool is unable to capture the short DRDY pulses. You may want to zoom into the section for SD card access or try with an oscilloscope with increased record length to capture.