ADC precision RAK 4270 and future RAK 3172

I’ve been using 4270 with an external i2c ADC with ADC internal Vref. Now with the new release of RAK 3172 i saw more ADC ports which is what i need. But without the exposed Vref pin of STM32 i can’t take accurate measurements with it. Right? Is there a workaround?

Many thanks in advance,

Pedro Dias

Hi @xistoso , welcome to RAK forum :slight_smile:

It is nice to hear that you use RAK4270 on your project.

Regarding RAK3172, it sad that there will be no external voltage reference. Vref+ pin is only available on UFBGA73 package of STM32WLE5. We are using UFQFPN48 package on RAK3172.

You can still use interval Vref though of STM32WLE5 via VDDA suppy.

VDDA pin though is directly connected to VDD of the module which is not configurable.

I suggest you evaluate the interval vref first. If the accuracy you needed is not achieved, then you have to use the same solution you have for RAK4270 which is external ADC.

Ty for the prompt reply @carlrowan . Guess i will have to test my buck-boost converter in a prototype, check vdd and see if it is stable during an adc reading. I can compare to the internal ref and it might work, i just checked and i only need 25 point resolution in the 12bit.

The cost saving in using the new product is to good to be true :slight_smile:

I see. I hope you’ll got good ripple readings on your buck-boost.

Btw, if there’s still anything you need to know on our new RAK3172 modules, just let us know :100: