pwm rates can not be set more than 400hz

[feemi]

Describe the bug
pwm rate parameters range is -1 to 2000 however you can not set more than 400hz. It sets to 400 if you try to set more than this value.

To Reproduce
Steps to reproduce the behavior:

1. open mavlink console

2. run pwm rate -r 600 -c 1234 command

3. run pwm info command

4. See values limited to 400 hz

Expected behavior
pwm rates should be set as desired.

Log Files and Screenshots

Add screenshots to help explain your problem.

Drone (please complete the following information):

• pixhawk cube 2.1 fmu v3
• px4 v1.9.2

[feemi]

It seems that solution can apply this chunk of code in registers.c file
But I dont think this values should be hardcoded like this.
Is it okay to add min max values to drv_pwm_output.h ?

		case PX4IO_P_SETUP_PWM_DEFAULTRATE:
			if (value < 25) {
				value = 25;
			}

			if (value > 400) {
				value = 400;
			}

			pwm_configure_rates(r_setup_pwm_rates, value, r_setup_pwm_altrate);
			break;

		case PX4IO_P_SETUP_PWM_ALTRATE:

			/* For PWM constrain to [25,400]Hz
			 * For Oneshot there is no rate, 0 is therefore used to select Oneshot mode
			 */
			if (value != 0) {
				if (value < 25) {
					value = 25;
				}

				if (value > 400) {
					value = 400;
				}
			}

			pwm_configure_rates(r_setup_pwm_rates, r_setup_pwm_defaultrate, value);
			break;

[mwiatt]

The standard in RC PWM control is a 1ms pulse indicating "low" and a 2 ms pulse indicating "high". A 400 Hz update rate gives a 2.5 ms period. Anything much more than a 400 Hz update rate would not allow a 2ms pulse to get through. That is why the PWM refresh rate is capped at 400 Hz.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. Thank you for your contributions.

[FlavioTonelli]

I'm right now facing the same issue trying to use a 500Hz esc on our multicopter. I mainly tried every possible workaround without finding a solution.
Do you guys know where the 400 Hz cap is enforced? Even removing the code pointed by feemi has no effect on the final rate. @julianoes any tips on hint?

[FlavioTonelli]

My bad. I confirm the Pam rate is capped in the code showed by feemi.
I got crazy for two days just for a make clean. PX4iofirmware is not recompiling without cleaning the build folder.