How to enable measurement with 3 operational amplifiers and 3 ADCs in Motor SDK 5.Y.3 for STM32G431CB microcontroller?

[DTort.1]

I am making my custom board based on the B-G431B-ESC1 board and do not understand how to make the same analog measurement with 3 op-amp and ADC channels. For some reason, there is no choice of 3 op amps from the drop-down list, only 2.

[cedric H · Accepted solution]

Hello @DTort.1​,

The B-G431B-ESC1 is a bit special because it uses a new feature of the G4 that allows to connect an OPAMP output directly on an ADC channel without going through a Pin.

The B-G431B-ESC1  uses 3 Opamps but only 2 ADCs. The Opamp3 output goes alternatively to ADC1 and ADC2 with the use of ADC2 VOPAMP3 channel. This is doable only because we use internal gain. Otherwise you always need the OPAMP output available on the external pin.

So to make the story short, if you want to use exactly the same configuration than the ESC, you have no other choice than starting with the ESC.

The MC Workbench has been designed far before the availability of the STM32G4, and all these new configurations offered by these new MCUs have a very limited support. We are working on a new workbench to fix all these issues.

Regards

Cedric

[DTort.1]

Thanks for the answer! Yes, I am doing this now, changing the design of the B-G431B-ESC1 board.

[cedric H]

Ok, Just be careful you must use an internal gain. If you want to use an external gain, you can do it, but you need an external wire between OPAMP output and ADC pin, and small software modification. And another point if you design your own board, the polarization of our amplification circuit is not the state of the art in this schematic. You could improve it to reduce the common-mode noise rejection.

Cedric

[DTort.1]

Yes, I get it, I am using internal Opamps, my circuit in this respect is almost identical to the B-G431B-ESC1.

Tell us more about improving polarization, I have already assembled the first version on STM32G431CBT and it works well and is assembled from the Motor SDK for STM32G431CBU, but I am still thinking about improving this design.