Fuel flow sensor using GPIO pins: pull-up voltage

Hello,

I am going to implement a fuel flow sensor that inputs the pulse signal to the GPIO / AUX ports on the standard carrier board (we have both Black and Orange cubes). I am following this documentation:
https://ardupilot.org/plane/docs/common-fuel-sensors.html

It is not 100% clear to me if the 3.3V pull-up is provided by the Cube as long as the AUX pin is configured correctly, or should I provide the voltage from somewhere else. The resistor has to be external, this is clear from the documentation.

Follow-up question: if external voltage for pull-up is required, can we use 5V, are the GPIO / AUX pins tolerant? Does it matter if Cube Black / Orange, if I remember correctly the PWM OUTPUT can be changed 5V with the Orange Cube (there is a parameter for this).

Best Regards,
Tomi

The servo rail on carrier board does not provide power. You have to supply voltage to it so that you could power any device connected there.
You may check the voltage range from docs.cubepilot:
https://docs.cubepilot.org/user-guides/autopilot/the-cube-module-overview#summary

For the PWM voltage level, you may have a look at this topic:

5v is possible from the cube Orange and yellow. On the IO pins, there is a parameter to switch between 3.3 and 5. All other Cubes and Pixhawks are 3.3v out

I understand this. I know how I am going to power the sensor. My question is only about the signal pin.

For the PWM voltage level, you may have a look at this topic:
Relay voltage? - #4 by Kravos

This topic concerns output functions, but it is not helpful to me, since I am using the GPIO / AUX signal pins as inputs. I think I will do some testing to see if the 3.3V is present in the pin after it is configured as an input.

When AUX OUT is being used as GPIO, it doesn’t need external pull-up.
3.3-5V is okay for the input PWM signal. There is a voltage converter inside which scales the input signals to 3.3V before feeding to MCU.

OK, Thank You. I think this should be explained in more detail in both ArduPilot and Cube documentation.

For future reference and interest I post the parameters I am planning to use:
BRD_PWM_COUNT = 4 (default) // AUX 6 & 5 reserved for GPIO or relay
RELAY_PIN = -1 (default 55) // disabled, AUX 6 is not relay
RELAY_PIN2 = -1 (default 54) // disabled, AUX 5 is not relay
BATT3_MONITOR = 11 (default 0) // fuel flow = 11
BATT3_CURR_PIN = 55 // AUX 6 used as input from fuel flow sensor