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
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 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. |