Notice on my two new Jetson Nano B01 4Gb development kits that pin4 (PWM) of the fan header J15 appears to be missing any form of pull down resistor and this results in a PWM fan running full speed when the Jetson Nano is powered down / off.
The fix appears to be a 3.3K resistor from pin4 to ground. This does not seem to impact the PWM management capability of the development kits. But I am interest to know if this is a known issue. Thanks
Are you testing with default software settings? And it will be fixed by adding a 3.3K pull-down instead of original 100K?
Using default out of box settings. And there does NOT appear to be any pull down resistor from the pin 4 of J15 - hence my question as to the possibility that the reference design my have not included a pull down resistor.
Tested with 33kOhm and this was insufficient to pull the residual voltage on the PWM pin -
Tested with multiple 5v pwm fans including Noctua.
There is 100k pull-down (R516) to pin 4 of J15, you can get that in P3449 schematic in DLC: Jetson Download Center | NVIDIA Developer. You can probe the pwm signal to see if it is under control of GPIO_PE7 (fan_pwm).