# I2C Fan Controller v2

~ because I found a cool new microcontroller ~

This one is based on WCH CH32V003 and it's (should be) much better than the shitty ATTiny one.

The `i2c_driver.h` is copied wholesale from ch32fun i2c_slave examples folder. It literally just works.

RPM readings are getting unstable at ~310-320 RPM but that's probably okay.

## How compile?
There's a Makefile shithead

We compile on Debian/ubuntu. Other than the usual `build-essential` stuff you need also
```bash
sudo apt install gcc-riscv64-unknown-elf libnewlib-dev libudev-dev libusb-1.0-0-dev
```
There is a distrobox.ini provided.

You will also need to clone the [`ch32fun repo`](https://github.com/cnlohr/ch32fun) somewhere and modify the `Makefile`.
To flash you will also need to compile `minichlink`. Included in the `ch32fun` repo. 

### ???..

Or just use PlatformIO idc. It has debugging.

## Pins

For the TSSOP20 package, CH32V003FxPx

| Pin # | Port | Function |
|-------|------|----------|
| 3     | PD5  | TX       |
| 4     | PD7  | NRST     |
| 11    | PC1  | SDA      |
| 12    | PC2  | SCL      |
| 16    | PC6  | POWER_EN |
| 18    | PD1  | SWIO     |
| 19    | PD2  | PWM_OUT  | 
| 20    | PD3  | TACH_IN  |

## Register index

Registers are 8 bit each, but most of them hold 16-bit values.
Bytes in even registers are high, bytes in odd registers are low.

| Register address | Function                                                  | R/W |
|------------------|-----------------------------------------------------------|-----|
| 0x00, 0x01       | whoami (always returns 0x69 0x2b)                         | RO  |
| 0x02, 0x03       | Current fan speed (RPM)                                   | RO  |
| 0x04, 0x05       | Target fan speed (RPM). Initial default speed is 750 RPM. | R/W |
| 0x06, 0x07       | Current duty cycle                                        | R/W |
| 0x08, 0x09       | Maximum duty cycle                                        | RO  |
| 0x0a             | State register                                            | RO  |
| 0x0b             | Mode register                                             | R/W |

### State register
State equal to 0 means all is good.

| Bit          | Description                                                                                                                                              |
|--------------|----------------------------------------------------------------------------------------------------------------------------------------------------------|
| 0 (0000000x) | Steady state flag. **0** - fan reached the requested target speed or fan running in constant duty mode. **1** - fan didn't (yet) reach the target speed. |
| 1 (000000x0) | Fan stalled. **0** - fan operating normally. **1** - fan stalled.                                                                                        |

### Mode register
| Bit          | Description                                                                                                                                                                                                                                                                                   |
|--------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| 0 (0000000x) | Mode of operation: **0** - Constant duty cycle mode, the controller will keep the fan at a duty cycle set in register 0x06 and not change it automatically. **1** - Constant RPM mode, the controller continuously adjust PWM duty until target RPM is reached. **This is the initial mode.** |
| 1 (000000x0) | Fan power disable: **0** - Fan operates normally. **1** - 12V supply to the fan is cut.                                                                                                                                                                                                       |