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https://github.com/tmsmr/cm4iofan
Simple utility to get/set the PWM duty cycle and to measure the RPM for a fan connected to the 4-pin header on the CM4IO.
https://github.com/tmsmr/cm4iofan
compute-module-4 emc2301 golang
Last synced: about 1 month ago
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Simple utility to get/set the PWM duty cycle and to measure the RPM for a fan connected to the 4-pin header on the CM4IO.
- Host: GitHub
- URL: https://github.com/tmsmr/cm4iofan
- Owner: tmsmr
- License: mit
- Created: 2021-10-14T16:22:58.000Z (about 3 years ago)
- Default Branch: main
- Last Pushed: 2021-11-27T16:53:32.000Z (about 3 years ago)
- Last Synced: 2024-06-21T21:08:02.165Z (7 months ago)
- Topics: compute-module-4, emc2301, golang
- Language: Go
- Homepage:
- Size: 11 MB
- Stars: 5
- Watchers: 1
- Forks: 2
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
Awesome Lists containing this project
README
# cm4iofan
*Simple utility to get/set the PWM duty cycle and to measure the RPM for a fan connected to the 4-pin header on the CM4IO.*
## Requirements
- Enabled `i2c_vc` overlay (`dtparam=i2c_vc=on` in `/boot/config.txt`)
- Loaded `i2c-dev` module (e.g. `modprobe i2c-dev` or using `/etc/modules`)
- A user in the `i2c` group (or `root`)
## Using the Go Module
```go
import "github.com/tmsmr/cm4iofan"
...
ctrl, err := cm4iofan.New()
if err != nil {
panic(err)
}
err = ctrl.SetDutyCycle(50)
if err != nil {
panic(err)
}
```
## Using `fanctl`
- Build with `cd fanctl && go build`.
- For every tagged version of the Go Module, the `fanctl` utility is built in a GitHub Action (Available on the Releases page).
```shell
$ fanctl set 50
$ fanctl get
50
$ fanctl rpm
2623
```
## POC with thermal monitoring
You may use https://github.com/tmsmr/chilld as thermal controller on your Raspberry Pi Compute Module 4 IO Board.
## Comments
### Direct Setting mode vs. Fan Speed Control mode
The EMC2301 has a built-in closed loop Fan Speed Control algorithm (Besides many awesome features), that allows the user to select a target RPM which is controlled by a PID.
I opted for the Direct Setting mode, because it feels more natural to me (Yes, i know that duty cycle/RPM is far from linear...).
### Should i use this for my 24/7-running project?
If you want nothing but a reliable/automatic cooling solution for your CM4IO, you should probably go with something like https://github.com/neg2led/cm4io-fan.
There are scenarios where this Module might be handy (Well, that's why i built it...). But keep in mind, all you do with it, is setting the fan's PWM signal:
- Some fans won't stop with 0% duty cycle.
- Most fans will stall with a low duty cycle.
- ...
### TACH to RPM conversion
Unfortunately it is not possible to detect RPM's lower than 500 using the EMC2301. That's why the RPM measurement returns a `RPMResult`:
```go
type RPMResult struct {
Rpm int
Stopped bool
Undef bool
}
```
- When the PWM duty cycle is set to 0%, `Stopped` is `true`. This is only true for fans that are able to stop completely!
- When the calculated RPM is below 500 (smallest value could be 480), it is not possible to determine the real RPM. In this case `Undef` is `true`.
### On poles, edges and ranges...
The EMC2301 may be used to control a wide variety of PWM fans. TACH measurement works different based on the fan's design type (emc2301.pdf: 4.4 Tachometer Measurement).
Noctua's PWM specification states that (regardless of the actual motor design) the tachometer always pulses two times per revolution (Emulating a fan with 2 poles). I **think** this is true for other regular, modern PWM fans. That's why i settled with the following values for the RPM calculation:
- *poles = 2*
- *n = 5*
Since i wanted to measure RPM's as low as possible, *RANGE[1:0]* is set to 500 RPM. This means the TACH multiplier is *m = 1*.
Using these values, a simplified formula for TACH conversion can be used (emc2301.pdf: EQUATION 4-3).