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Original question:

ADS1220: Interfacing ADS1220 with stm32

ADS1220: ADS1220 SPI connexion to STM32H7

Karcel Zabieru
Prodigy 65 points
Part Number: ADS1220

Dear TI,
this is always a great pleasure to use your product and namely the ADS1220 24-bits ADC to be used with RTD 3-wires.
Actually this thread is a follow-up of the [1] thread about the ADS1220-EVM tests.
This time we want to validate the hardware connexions between the ADS1220 and a STM32H7 MCU following the below attached schematic

AVDD=DVDD=3V3
SPI_MOSI, MISO and CLK connected over 47ohms resistors to the SPI1 of the STM32H7 (3V3 signals).
CS connected to a GPIO_OUT on the STM32H7
DRDY connected to a GPIO_IN on the STM32H47

With this schematic currently we cannot read values or detect the device on the SPI1 bus.

Beforehand with different tests (CS to low, monitor DRDY pulses to see if AVDD and DVDD are correctly connected) I wanted to check the schematics with you.

Is there a simple way to validate that the SPI connexions is correct from the ADS1220 point of view ?

Much regards,

Zabieru.

[1] : e2e.ti.com/.../ads1220evm-rtd-pt100-3-wires-test-with-ads1220evm-configuration

  • 0
    TI__Expert 4680 points

    Hi Zabieru,

    Will take a closer look and get back to you early next week.

    Best Regards,

    Angel

  • 0
    TI__Expert 4680 points

    Hi Zabieru,

    You won't see DRDY toggle until the issue START/SYNC, and the default mode is single-shot so this will only happen each time after the START/SYNC unless they configure to continuous mode.

    The schematic appears to be ok, so in these types of cases it is best to suggest they compare the communication to the timing diagram in the datasheet, using a logic analyzer or oscilloscope would be useful for this. 

    Most common issues are with clock phase and CS framing as CS must be held low throughout the entire communication transaction.

    Best Regards,

    Angel

  • 0 in reply to Angel Rodriguez de San Miguel Bermudez
    Prodigy 65 points

    Hi Angel,

    thanks for your feedbacks.
    1.single-shot, continous or other mode
    We need to set the mode we wish to use from the mcu. I believe using the DRDY signal as an IRQ to trigger a measure would be nice ? We want to sample regularly (like 10SPS) to be observe the changes on the RTD PT100 sensor quite often.
    Which mode would you recommand ?
    2.schematics validation
    Thanks a lot for that and we will have 8 ads1220 in parallel on the same SPI bus but at 10SPS I don't see an issue yet for a 1MHz SPI bus, don't you ?

    Best regards,
    Zabieru.

  • +1 in reply to Karcel Zabieru
    TI__Expert 4680 points

    Hi Zabieru, 

    1) Either mode will work fine.

    Writing to the configuration registers starts a conversion regardless of the mode the device is in.  If the device is already converting, the conversion will restart once the register has been written. If the device is in single-shot mode, the device will take one conversion and stop.

    The following diagram shows the timing diagrams for reading data for both continuous conversion mode and single-shot mode.

    Section 8.5.4 to 8.5.6 of the data sheet talks in detail about how to communicate with the device and shows example timing diagrams.

    2) This should work ok.

    Best Regards,

    Angel

  • 0 in reply to Angel Rodriguez de San Miguel Bermudez
    Prodigy 65 points

    Dear Angel,
    thanks a lot for your feedbacks on the schematic and the different mode in regard to the timings.
    I will now implement everything and get back to you once the system is in place if I have any issue.
    Please take care of your self and thanks a lot for your help.
    Regards,
    Zabieru.