https://github.com/crycode-de/attiny-i2c-fan-control

Control a PWM fan over the I²C bus.
https://github.com/crycode-de/attiny-i2c-fan-control

attiny avr fan-controller i2c-bus platformio

Last synced: about 1 month ago
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Control a PWM fan over the I²C bus.

• Host: GitHub
• URL: https://github.com/crycode-de/attiny-i2c-fan-control
• Owner: crycode-de
• License: other
• Created: 2021-03-05T15:15:12.000Z (almost 4 years ago)
• Default Branch: main
• Last Pushed: 2021-09-12T14:02:27.000Z (over 3 years ago)
• Last Synced: 2024-05-01T12:17:08.529Z (8 months ago)
• Topics: attiny, avr, fan-controller, i2c-bus, platformio
• Language: C++
• Homepage:
• Size: 39.1 KB
• Stars: 7
• Watchers: 2
• Forks: 1
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • Funding: .github/FUNDING.yml
  • License: LICENSE.md

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README

        
# ATtiny I²C Fan Control

Control a PWM fan over the I²C bus.

**Tests:** ![Test and Release](https://github.com/crycode-de/attiny85-fan-control/workflows/PlatformIO%20CI/badge.svg)

*ATtiny I²C Fan Control* is made as a [PlatformIO](https://platformio.org/) project.

## Supported features

* Set fan speed by using a PWM signal

* Set fan speed via I²C bus

* Read the current fan RPM via I²C bus

* Auto adjust PWM range by testing the connected fan at startup (can be re-triggered by I²C bus)

* Override min PWM level by I²C bus

## Currently supported AVR controllers

* [ATtiny85](https://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-2586-AVR-8-bit-Microcontroller-ATtiny25-ATtiny45-ATtiny85_Datasheet.pdf)

Adjustments for other AVR microcontrollers should be easy.

## I²C registers

| Register | Description |

|---|---|

| 0x00 | **Status** - By writing a 1 to bit 0 of this register you can trigger a re-calibration of the fan. |

| 0x01 | **Fan speed** - By writing to this register you can set the fan speed. A value of `0` means "fan off" and `255` is full speed. |

| 0x02 | **Minimal PWM level** - Read or write the minimal PWM level at which the fall will rotate when *fan speed* is set to `1`. This will be detected automatically at startup. |

| 0x03 | **Current fan speed in revolutions per second (RPS)** - Read the current fan speed in RPS. This is calculated from the fan tacho signal. |

| 0x04 and 0x05 | **Current fan speed in revolutions per minute (RPM)** - Read the current fan speed in RPM. This is calculated from the fan tacho signal. `0x04` is the low-byte and `0x05` the high-byte. |

### Hint on I²C bus

Since the ATtiny microcontrollers use a USI (Universal Serial Interface) to provide the I²C bus, there may be some problems reading or writing more than one byte at once.  

To overcome this issue you should read/write byte by byte, even if want to read the fan speed in RPM.

## Wiring

![Wiring](./doc/attiny-i2c-fan-control-wiring.png)

## Projects using ATtiny I²C Fan Control

* [Active cooling of the "HomePi"](https://crycode.de/homepi-kuehlung) (German)

## Used Libraries

* [Arduino Framework](https://platformio.org/frameworks/arduino)

* [PinChangeInterrupt](https://platformio.org/lib/show/725/PinChangeInterrupt)

* [TinyWireSio](https://platformio.org/lib/show/293/TinyWireSio)

## License

**CC BY-NC-SA 4.0**

[Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-nc-sa/4.0/)

Copyright (C) 2020-2021 Peter Müller  [https://crycode.de](https://crycode.de)