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Troubles with AD5142

Hi! I cann't control AD5142 with stm32f4 by SPI. I connect AD5142 like rheostat in feedback of op amp (for amplifing). Scheme in attach. But when I send some data via SPI to AD5142 it don't answer and Vout isn't change. For change resistance, I send b0001000000000001 (in 16bit mode SPI in stm32f4), then I change data to b0001000011111111 and there is no result, Vout isn't change. Oscilloscope picture correct and looks same like in datasheet. What am I doing wrong? Is it necessary to send some preparation data to AD5142, before set resistance? Could some one post tested sequential data for change resistance in AD5142?

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  • Are you sure you are activating the Reset and Sync pins correctly on the device to load the clocked in data?

    Are you using HW SS on the STM32? I have had issues before where the HW NSS pin did not behave correctly at the end of the bus transaction and remained low. 

    Have you checked your clock phase and polarity and how you are shifting out the data (MSB or LSB first)?

    I would start by trying to write a value to the EEPROM and then reading back the data before moving on to debug the opamp circuit

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  • Are you sure you are activating the Reset and Sync pins correctly on the device to load the clocked in data?

    Are you using HW SS on the STM32? I have had issues before where the HW NSS pin did not behave correctly at the end of the bus transaction and remained low. 

    Have you checked your clock phase and polarity and how you are shifting out the data (MSB or LSB first)?

    I would start by trying to write a value to the EEPROM and then reading back the data before moving on to debug the opamp circuit

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