How to capture 8 bipolar analog inputs simultaneously using STM32MP157D device?

[mrel22]

Since STM32MP157D requires positive analog input, I have added a fully differential amplifier to capture the negative inputs. STM32MP157D devices embed two analog-to-digital converters.

I have attached a diagram that explains my problem. I need to capture the 8 bipolar analog inputs simultaneously to get accurate phase information.

What is the best and optimal way of achieving this?

 

[Nigel Goodwin]

You can't as such, if there's only two A2D's, switched between the different inputs - then the most you could capture at the same time is two, assuming the processor has two cores, or DMA.

Exactly what are the inputs?, and why do you think you need to capture 8 at the same time?.

And why differential opamps?, why not just bias simple inverting or non-inverting ones?.

 

[danadak]

https://www.edaboard.com/threads/how-to-capture-8-bipolar-analog-inputs-simultaneously-using-stm32mp157d-device.402069/#post-1731893

Regards, Dana.

 

[mrel22]

Thank you all. Like you said, a few microsec delay won't have a significant effect on the phase.
I was thinking of starting from the sample design I attached and then go for other solutions like external ADC etc like you suggested.
I am using the differential amplifier to increase the input signal capture range.
Is there any problem with my design? If so, how can I make it better?
Any other simple and cost effective way to do this? Thank you again.

 

[rjenkinsgb]

What is the voltage range of the signals?
You can read +/- signals with an MCU DAC using nothing more than a resistor divider.

eg. Two equal series resistors from MCU V+ (or DAC REF) with the ADC fed from the junction gives you a range from V+ to negative the same value.

You can extend the range with a three resistor network.

 

[danadak]

There is a calculator (download) over here for translating - signals using resistor networks
tied to a positive Vref-

https://www.edaboard.com/threads/how-to-capture-8-bipolar-analog-inputs-simultaneously-using-stm32mp157d-device.402069/

Regards, Dana.