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ads1256 DRDY and timing

Gerald Faulhaber
Prodigy 20 points

Other Parts Discussed in Thread: ADS1256

Hello,


i have a general question regarding the /DRDY.

Does this pin always toggle  so that i can use it as trigger for sending data via SPI to the ADC.

I want to simplfy my commication via SPI, and as i read in other threads, there was often the hint to look at the DRDY.

I think of the following:

If DRDY = 1, ADC is busy -> do no communication via SPI

if FallingEdge(DRDY) then ready for communication via SPI.

In general, it is save to trigger always on the falling edge of the DRDY and then start SPI communication?

Or are there situations where DRDY stays low (no falling edge) and does not toggle?

An other question is,

on page 6 in the timing characteristics for figure 1.

t11 describes the waiting time to the next command. How long do i have to wait after command SDATAC?

Regards Gerald

  • 0
    TI__Mastermind 44780 points

    Hi Gerald,

    Welcome to the TI E2E Forums!

    Gerald Faulhaber said:

    In general, it is save to trigger always on the falling edge of the DRDY and then start SPI communication?

    Or are there situations where DRDY stays low (no falling edge) and does not toggle?

    In general, when the ADC is converting, DRDY will be toggling. If you read the data or send other commands, DRDY will return HIGH. If you do not read the ADC data before the next conversion completes, then DRDY will create a short pulse to indicate new data. Sending/triggering SPI commands after a DRDY falling edge should be okay.

    Regarding the SDATAC timing, I don't think you need to add a delay. If you want to be safe, use the same delay as the RDATAC command. I'll see if I can find out more information about this.

    Regards,

    Chris

  • 0 in reply to Christopher Hall
    TI__Mastermind 44780 points

    Hi Gerald,

    I'm just following up on this open E2E issue. Were you successful in communicating to the ADS1256?

    I recently learned that the SDATAC command does require a small delay. I am not sure exactly how many clock cycles; however in my experience interfacing to the ADS1256, I have never encountered an issue with sending a command immediately after SDATAC. Usually, the microcontroller will have some inherent delay between SPI commands which is sufficient.

    I would be curious to know if you added a delay and how long it was!

    Best Regards,
    Chris