RPM measurement on Omnibus F4 V3 does not work

I would like to connect the rpm out from my Hobbywing Platinum V3 ESC to PWM6 on my Omnibus F4 V3 to measure and log RPM.
The ESC puts out a valid 3.3V signal if not connected to the FC.
The signal disappears as soon as connected to the FC.
I assume the PWM6 is still configured as output.

I have set the following parameters following the Wiki.

RPM_PIN = 55
RPM_SCALING = 1 # for testing

ArduCopter-Heli 3.6.10

3.6.10-20190924.param (14.2 KB)

Do you know what type of signal the ESC is sending?.
I think it’s a PWM, so you need to change the input to that.
In any case, it’s worth sticking a scope on the output and see what type of signal it’s sending.

(Edit! I should learn to read…you did have set to PWM…still worth testing what type of signal you’re getting).

The ESC sends a 3.3V frequency signal, not pwm.
I have measured the signal with a scope already.

From the wiki:

The parameter RPM_TYPE should be set to 2 when using the AUX pins on Pixhawk type boards. It should be set to 1 in all other instances.

Oh hang on.
You need to use the GPIO pins for this. These are typically channels 9-14, depending on board. I’m not sure that the Omnibus F4 has any GPIO pins.

Also what do you mean by frequency signal? If it’s not a PWM signal, then it needs to be set to 2.

I have asked here if it’s possible to measure rpm with controllers other than pixhawk.
I assume if a pin is PWM or GPIO depends on the firmware, not hardware.

Every rpm sensor sends a frequency signal, not pwm.

Here is what the manual of my ESC says:

【Output Port for RPM Signals】
• Platinum V3 series of speed controllers have independent output ports for RPM signals.
• Specification for interface signals: It is the periodic signal with duty ratio of 17%, and 0V for low level, 3.3V for high level.
• It represents the electric rev of the brushless motor (electric rev means the rev of a 2-pole brushless motor). And here is the formula used for converting the actual rev of multi-pole brushless motor into the
electric rev of 2-pole brushless motor:
Electric rev = Actual rev of the multi-pole brushless motor × Pole number ÷2
E.g. the actual rev of a 12-pole motor is 5000rpm, so its corresponding electric rev is: 5000 × 12 ÷ 2 = 30000rpm

You are right.
I made another test with RPM_TYPE = 2 and it works as it should.

RPM_PIN = 55
RPM_SCALING = 0,01444444444444444444444444444444