STM32L476 Interleave and opamp

[Stm325]

Hi, I am sampling high rate data using STM32L476 in Nucleo64 board in dual channel interleave mode. I am measuring very low voltage values so is it possible to use MCUs internal opamps together with interleave mode. It looks like I am not able to activate interleave mode when I activate opamp and I couldnt find information on whether or not they can be used together. What I would like to do is basically amplifying my signal before entering to ADC without any external component. I appreciate any advice.

[mƎALLEm]

Hello,

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@Stm325 wrote:

It looks like I am not able to activate interleave mode when I activate opamp 

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What do you mean by that? what is the issue? errors in ADC readings? enable to enable both ADC and OPAMP? or what? did you manage to make it works with a single ADC reading?

Please provide more details about the issue.

See the tips on posting.

[Stm325]

Hi, sorry for insufficient explanation. By "I am enable", I meant that the dual mode option was not there but I think I selected a wrong channel because I am able to select it now but I still have some questions. I enabled IN15 as OPAMP2 Output Single- Ended for both ADC1 and ADC2 and selected "Dual Interleaved Mode Only". I have 2 questions in mind:

1) As I said I want to capture low voltage signals so I figured it would be a good option to reduce reference voltage and I found this part in MCU datasheet: 

In ADC1 settings, there is a checkbox:

Is it enough to set it to shift Vref from 3.3 to 2.048 or how should I set my reference voltage to 2.048?

 

2) I am not sure how to configure OPAMP2, I need 2 things, one is to offset the signal for like 200mV(To shift it completely to positive side) and other is to amplify it. I understand that I should be able to do both from what is written in this document: https://www.st.com/resource/en/product_training/STM32L4_Analog_Opamp.pdf

I am not sure if I can set this with PGA not connected, also PB0 is for sampling the amplified signals but I am not sure what PA6 is for, I will not be amplifying my signal shifting it more than 1V so I think I also should be able to do it without giving an external bias. 

 

I have looked through some application notes but could not exactly figure out how to set these for my needs so I appreciate any advice. 

 

[mƎALLEm]

Need to close this thread as you solved your first question by adding what solved the issue and mark it as solution and open a new thread for the new question.

Thank you for your understanding. 

[Stm325]

The issue was that I was trying to enable dua ADC mode from ADC2 which is the slave ADC in dual mode but I did not realize I was checking the ADC2, mode options were available in ADC1 including Dual Interleaved Mode.