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AD7381-4: Changes in the configuration register shows no effect / soft reset resets register

Category: Hardware
Product Number: AD7381-4

I am using the AD7381-4  ADC with a STM32F4 microcontroller. The end goal is, to use quad SPI to get all the data I need.

At the moment, I try to communicate with the ADC using SPI only.

I am able the read and write the configuration register.

But it seems, that the changes I've made in the configuration register show no effect.

Here are some measurement I've done on the data lines:

Channel 0 is the CS line

Channel 1 is the SPI clock (SCLK)

Channel 3 is the MOSI line (SDI)

Channel 2 is the the MISO line (SDOA)

Channel 4 is the SDOB line

Hard reset and config register read.

Write to the register (enable 1-wire conversion in configuration register 2).  Reread the configuration register.

Initiate a soft reset. A nop command was send beforehand.

register read after soft reset. As you can see, the register have been reset.

Finally. Reading the ADC value.

As you can see in my measurement, I still get data on both SPI lines (as 2-wire conversion is the default value) after changing to 1-wire only.

I've tried to do a software soft reset, to see if that helps. But the soft reset also resets all the registers (according to the datasheet it shouldn't).

 I also tried to change the baudrate but with no different outcome.

Any pointer in the right direction is apprichiated.


  • Hi Eeteler,

           Apologize for late reply. When a write to register and the device does not reflect the value written, I normally double check on the timing. But in your case writing to register seems working fine as you mentioned the reset function is enabled when writing to do Reset. I saw that you wrote 0xA300. Can you try writing 0xA100 instead. 



  • Hi Jonathan

    Thanks for the reply.

    I turned out it was some sort of chip issue. I built  a second board with the same firmware and it worked fine.

    I don't know where this comes from, but ESD-damage seems the most likely.


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