Repurpose Fan PWM

We are attempting to use the fan PWM to control a piezo electric buzzer - but it doesn’t seem to be functional on our custom PCB.

Is there a trick to making the PWM generate an output when not on the Jetson TX1 development board?

Could the issue be that the tachometer line is not sensing RPMs, so the PWM refuses to generate output?

Is it also possible that this is due to the missing TI INA3221? If so, is there a device tree update required to make this function?

Thank you!

Hello,

I will be looking into your issue. When your say it does not seem to be functional, have you only not observed an output from your buzzer or have you tested the PWM with a fan, for example?

Hi Mike,

The file: /sys/kernel/debug/tegra_fan/target_pwm doesn’t exist when booted up on our carrier board, but is present when running on the Nvidia development board

Thanks,

Mark

Missing the file implies missing the driver since this is not a real file, and is simply something created by the loaded driver. One reason a driver might not load is if it can’t find the hardware, and on a custom carrier board you will possibly need to alter the device tree depending on how that function is wired. Sorry, I am not able to provide specific device tree changes, but you will likely want to mention what device tree changes you’ve made, how the wiring may differ related to the PWM wiring and any power rails related to the PWM.

You can examine your current device tree in source form via this (you might need to “sudo apt-get install device-tree-compiler”):
dtc -I fs -O dts -o extracted.dts /proc/device-tree

HI mumi1048576
I have the same problem as you. Have you solved it? How was it solved?
Can you help me?

Hi @1481453418,

I have not solved this yet - we shifted focus away from it for the moment, but will be returning to it.