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ADS1292: Stops interrupts randomly

Thermoos
Prodigy 50 points
Part Number: ADS1292
Other Parts Discussed in Thread: ADS130E08

Hello,

I am developing pcb board with ADS1292 and I am having issues with receiving data from ADS. 

Firstly, here's my ads schematic:

Both Voltages (VCC and AVCC are 3.3V).

I would like to use ADS1292 in 2 electrode configuration (that means without external RLD) , however I added both channels on pcb, because it's prototype and i wanted to test this chip.

Problem is, i can get it to work in any configuration I try (despite channel i chose). Is there anything particularly wrong in this schematic?

My software on STM board waits for DRDY signal and then reads 9 bytes of data. I try to read 15k samples (with 125SPS rate).

My problem is, chip acts kind of strangely. Sometimes it will read just a few samples (let's say up to 150), sometimes it won't even read 10 samples, and sometime's it will read everything (in that case, mostly zeros).

Thing that I would love to add is that I am successfully reading / writing registers or sending commands to ADS. 

This are my registers settings:

REG_CONFIG1, 0x00
CONFIG2, 0xA0
CH1SET, 0x81
REG_CH2SET, 0x60
RESP2, 0x07
RLD_SENS, 0x20
LOFF, 0x11
REG_LOFF_SENS, 0x00
LOFF_STAT, 0x10
RESP1, 0x02
GPIO, 0x0C

I hope I provided enough information!

Thank you in advance for help!

 

@Update:

Quick update, I managed to find out, that chip resets during data reading, because if I am able to receive 15k samples, the values of registers (checked after data reading) are different (they match reset values form datasheet p.39)

  • 0
    Prodigy 145 points
    Did you figure why the chip resets? I am having a similar behavior with the ADS130E08 chip, after few SPI Read requests, Data Ready does not go low anymore
  • 0 in reply to Jean Paul Talledo
    Prodigy 50 points
    I haven't, but I am trying to resolve issue.
    Whenever I find solution I'll post it here.
  • 0 in reply to Thermoos
    TI__Intellectual 2885 points
    Hi Thermoos,

    One thing I see is that could be causing the part to rest is your PWDN/RESET pin is tied to ground. If there is any fault or delay from the GPIO the pin will be grounded thus resetting the 1292. If there is any interrupt while you are sampling you can check this by probing the RESET pin and setting it to trigger if it falls below DVDD. Ideally the RESET pin should be held high and only pulled down when you want the part to reset.

    A hardware test would be to desolder the R49 from GND, rotate it and connect it with a wire to power, this will set the default state to active high (not reset). So if there is ever a delay or interrupt the part will not reset.
  • 0 in reply to Matt Mendez
    Prodigy 50 points

    Hi Matt,

    thanke You for replay. I managed to desolder R49 from GND and replaced it with 10k pull-up resistor.

    Unfortunately nothing has changed.

    Later on, i removed components from input 1 and input 2, here's schematic with removed parts:

    Unfortunately, nothing has changed again.

  • 0 in reply to Thermoos
    TI__Intellectual 2885 points
    Hi Thermoos,

    The only way the part can reset now is if the MCU sends a command to the RESET pin, overriding the hardware pull up. First, try and probe the reset pin, and see if the MCU is sending a signal pulling the reset pin low, if so something might be wrong with your code. Also, you can try completely disconnecting the RESET pin from the MCU so it is always active high.
  • 0 in reply to Matt Mendez
    Prodigy 50 points
    Hi Matt,

    Thanks for replay, I checked MCU and it's pulling reset pin down, I even disconnected RESET pin and used external 10k resistor as pull-up.
    Also, I don't send RESET command anywhere in my code and ADS still resets or stops converting in random places.
    The worst part is, there is no pattern to it's behavior and I have no clue what to do.

    Also, I re-soldered everything on 2nd pcb board (no changed whatsoever) and used 2nd copy of ADS1292. Nothing worked, chip acts the same, weird way.
  • 0 in reply to Thermoos
    TI__Intellectual 2885 points
    Hi Thermoos,

    A few more things you can try. Probe the digital supply pins. Makes sure they are operating properly. Also, probe the RESET pin even when it is disconnected from the MCU (IE just connected to the pull up). It should stay high the entire time. As you said, the register settings correlate to a RESET event. There's nothing else on the part that can cause this weird error other than the RESET pin. Let's be as thorough and redundant as possible.
  • 0 in reply to Matt Mendez
    Prodigy 50 points

    Hi Matt,

    I probed supply pins and reset pin and all seems fine. They stay high entire time.

    However, I measured voltage on VCAP2 pin (27) and it's equal 5.2V. Note that I use both supplies as 3.3V.

  • 0 in reply to Thermoos
    TI__Intellectual 2885 points
    Hi Thermoos,

    It's not mentioned in the datasheet but VCAP2 is a charge pump = AVDD + 1.8 V. This is why your seeing ~5.2 V.

    As for why the part is behaving abnormally. We've gone through every possible debug. If you want you can send us a board and we can look at it.