ADC_6V6 on a Holybro Pixhawk 6X,

We have some Holybro Pixhawk 6xs (abbreviated after this to “AFC” - autopilot flight controller). I have been asked to attach a sensor to the ADC1_6V6 input on the AD&IO port (line 7).

I looked in the forums and it seemed that in the past some of the boards weren’t 6V tolerant on any of their ADC inputs.

I’m asking for someone to reassure me before I attach stuff and damage the AFC.

I looked at the document “DS-012 Pixhawk Autopilot v6X Standard-3.pdf” found here Pixhawk-Standards/DS-012 Pixhawk Autopilot v6X Standard.pdf at 8b904c75e3a7aa62c074cc7721b944df4efb9d1a · pixhawk/Pixhawk-Standards · GitHub – and It looks like the ADC1_6V6 goes right into the STM32H753IIK6 chip.

I found a datasheet for the STM32H753IIK6 – it seems that the ADC inputs take max 3.3V. I found the datasheet on this page: Buy STM32H753IIK6 - ST Online Store

Given that the AFC is advertised as 6.6V tolerant, I assume there’s a voltage divider in there not shown on the block diagram.

I emailed Holybro but haven’t heard back from them. I looked for a schematic for the Holybro Pixhawk 6X - and couldn’t find one - but I read that the schematics are proprietary and aren’t online.

I did connect a low voltage (< 3V) to the ADC1_6V6 input. I believe the system is able to read it - I could change the input and the value displayed changed. I didn’t go over 3.3V.

As I don’t want to damage my AFC, I got myself a nucleo devboard from STM with a similar chip (STM32H753ZI). I assume I need to build a voltage divider to use that board with the sensor - at least then I’d have a similar board I could experiment with more freely.

So it looks like I’ll need to build a voltage divider to test the same sensor - likely with some noise filtering. If anyone has done this before, I would appreciate any tips. This is the sort of thing I found Voltage Divider into ADC - Page 1 – I would prefer to copy whatever someone has done that worked.

Let me ping @Vincentpoont2 here. He might be able to help.

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