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ADS1262: No convresion, /DRDY stay high

Vincent Kerbaul
Prodigy 40 points
Part Number: ADS1262

Hello,

I'm trying to read some data, but I don't get anything.

First, I'm able to read and write the registers.
I'm using the ADS1262 on Bipolar mode (+2.5/-2.5), and at 2400SPS PGA:1.

But I don't get any data, even using the continuous mode or pulse mode with start pin or command.
When I send a read data command, I get the status 0x21, so no new data on ADC1 (bit 6), and then DOUT stay low.

The /DRDY stay high all the time, so I suppose that there is no conversion made and I don't get why.

What can be the cause ?

Thank You,

V.Kerbaul

  • 0
    TI__Mastermind 44680 points
    Hi Vincent,

    It's very odd that you are able to read and write to the devices registers but don't ever see /DRDY go low...

    For /DRDY to start pulsing, all you need to do is power the device (AVDD & DVDD supplies), provide a clock (either externally or by grounding XTAL1 to enable the internal oscillator), and set the GPIO pins (nRESET/nPWDN = high, START = high) to ensure the device is active.

    If you have done that and still don't see /DRDY pulsing, then I would check the IC pin voltages to see if perhaps there is an open or shorted pin connection. When probing the IC pins, check to see if there is are any voltages on the BYPASS (2V) and REFOUT (2.5V) pins, as these are internal voltages that should be observable on their respective output pins.
  • 0 in reply to Christopher Hall
    TI__Mastermind 44680 points
    ...Also, do make sure that the analog and digital grounds are connected together, in case you have split grounding on your board.
  • 0 in reply to Christopher Hall
    Prodigy 40 points

    Thank you for the answer Chritopher,

    So I've try with both internal and external clock, on continue conversion mode with start pin, keep at high level.
    nRESET/nPWDN is high and /DRDY stay high also.

    I'm using bypolar alimentation, AVDD = +2.5V, AVSS = -2.5V and DVDD = +3.3V. So BYPASS = 2V and REFOUT = 0V

    I've also check ground connections.

  • 0 in reply to Vincent Kerbaul
    TI__Mastermind 44680 points
    Hi Vincent,

    OK...What about the START pin; is this pin being held high? If not, then you won't see any /DRDY falling edges without sending the START SPI command. For troubleshooting purposes you might try send START commands periodically to see if that triggers any activity on /DRDY.

    If you still having issues after checking the START pin, would you be able to share a schematic with me to help you look for other possible causes?
  • 0 in reply to Christopher Hall
    Prodigy 40 points

    Hi Christopher,

    I've already try different schem with the start pin.

    I'm using the ADS126xEVM (but without the mother board, one component is dead on).

    I've check the Onboard clock (7.3728MHz Crystal Oscillator) and I just get a continious signal at 1.5V.
    So maybe there is something with that (even if I got same result with the internal clock and with the Onboard clock).

    I want to try with an external clock with a fonctions generator, what is the carateristic signal that I can use?

    Thank you in advance

  • 0 in reply to Vincent Kerbaul
    TI__Mastermind 44680 points

    Hi Vincent,

    Here are requirements for an external clock signal:

    Notice that the clock signal amplitude should go below 0.3*V_DVDD and above 0.7*V_DVDD (with respect to DGND). Either square and sine waves should work.