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ADS 1262 DRDY pin is always high

Shubhendra Singh
Intellectual 885 points
Other Parts Discussed in Thread: ADS1262, MSP430F6779

hi,

I am trying to communicate with ads1262 with msp430f6779.

Problem : DRDY pin is high (2 volt)  from the begining. is it okay?.

I loaded a blank program in controller. remove spi jumper connection from controller to adc and even i removed the AVDD supply of 5 volt.  only  3.3 volt   was going in the DVDD pin still the DRDY pin showing 2 volt. is it okay?.

it may be because datasheet says  that DRDY pin is active low.

if that is okay when i send start1 command and then wait for it to go low but it didn't go low??

even i tried it with default configuration of registers but it does not go low.

any help or suggestions

thanks

thanks

  • 0
    TI__Mastermind 44680 points

    Hi Sasuke,

    The /DRDY pin should go low to indicate that the ADC has completed a conversion. If you do not see /DRDY go low, then there is an issue.

    Make sure to supply both AVDD and DVDD power supplies - both are needed for conversions to start. After powering up the device, wait 50 ms before communicating with the device, then send the "start1" command.

    I would double check /DRDY on a scope to see if it is going low and perhaps the controller is missing the interrupt.

    Best Regards,
    Chris

  • 0 in reply to Christopher Hall
    Intellectual 885 points

    hello chris,

                                   thanks for the reply.

    1.                    both the  pins {AVDD & DVDD} are connected to supply.
    2.                    i also thought that controller is missing interrupt but then cross checked it by toggling a pin in ISR. but interrupt is not occurring.
    3.                    then i debug a little more i found that when send START1 command and wait for conversion to complete using a flag  while(!DRDY_Flag);  my      program stays at this instruction.
    4.                    then i cross check the /DRDY pin by monitoring it on oscilloscope then i found that it is not going low.

    what may be the cause ?? i am totally stuck :)

  • 0 in reply to Christopher Hall
    Intellectual 885 points

    hi chris,

                    one more thing is troubling me(high and low level value of drdy pin) .  my drdy pin is showing 1.88 volt ????? i think it should show near to 3.3V as high .

                  supply voltage ( AVDD =5 V,   DVDD=3.3V ).[using adc in single supply operation]

    can anyone please confirm what should be the voltage level. If the voltage level should be 3.3V then my pin is neither high nor low. 

    thanks

  • 0 in reply to Shubhendra Singh
    TI__Mastermind 44680 points
    Hi Sasuke,

    The ADC's logic high voltage should be nearly equal to DVDD, as you say.

    Are you measuring /DRDY with a multimeter?
    If so, perhaps /DRDY is toggling and the multimeter is providing you with the average DC voltage

    Additionally, you might want to double check that your respective microcontroller pin (connected to /DRDY) is not configured as a GPIO output. This should be an GPIO input to the micro.

    Best Regards,
    Chris
  • 0 in reply to Christopher Hall
    Intellectual 885 points

    hello chris,

                        i am measuring the voltage level on oscilloscope. why it is  1.8 Volt. what it actually means.?

    Today i was trying to read the default configuration of registers and try to watch it in debugger . but all 21 register shows 0x00 value.

    how can i cross check that my communication is successfully established between my controller and ADC.

  • 0 in reply to Christopher Hall
    Intellectual 885 points

    Hello Chris,

    i want to reduce noise in my measurement.  i tried almost all data rates from 38k sps to 400sps with different filter configurations.


    i can't tolerate error above 10 micro volt in my application.

    how can i get more accurate result?????

    my input signal is 0-5 volt single ended signal. i am using precise external reference of 5 volt using REF 02.

                                 the below pic contain continuous sample of precise 2.5008 volt input signal at 4800 sps with sin4 digital filter

    why my count is varying that much when my reference is precise and input signal is precise