forked from rrcarlosr/Jetpack
27 lines
1.1 KiB
Plaintext
27 lines
1.1 KiB
Plaintext
kernel driver gpio-tachometer:
|
|
===================================
|
|
To measure cpu fan/motor speed using GPIO pin, this driver can be used.
|
|
The driver does not rely on any specific peripheral like input capture.
|
|
|
|
Author: Vishruth Jain <vishruthj@nvidia.com>
|
|
|
|
Description:
|
|
------------
|
|
|
|
In platforms where the motor speed input pin is NOT connected to input capture
|
|
pin or any other peripheral capable of measuring the frequency of external
|
|
signal, this driver can be used to measure motor speed.
|
|
The driver works by using GPIO IRQ.
|
|
|
|
Driver makes following assumptions:
|
|
-> The pin to which is motor tach output is connected is IRQ capable.
|
|
-> Motor speed indicator(tachometer output from motor) has default state high
|
|
and is pulled to ground level, 1 or more times for every full rotation.
|
|
|
|
Speed is calculated based on the number of times GPIO IRQ is triggered in a
|
|
time window. Speed in RPM(rotations per minute) is derived from the count
|
|
captured using IRQ.
|
|
Optionally driver supports creating a delayed worker, which monitors the motor
|
|
speed periodically. If the motor is stopped, indicated by speed being 0, the
|
|
delayed worker initiates system shutdown.
|