Re: RPi4B, POE+. Fan

On 11/01/2022 9:50 pm, Brian Scott wrote:
> Hi List,
> 
> Is there a known method to get the fan running on the rpi-poe+ board under FreeBSD?
> 

I would assume this depends on the board. You've not specified anything.

> It looks like it is controlled completely by the kernel in Linux land. Adding the rpi-poe dtb overlay has no effect on FreeBSD so I'm guessing there is no driver for it.
> 
>  From what I've read, its controlled by something on the iic bus used for HAT identification. Beyond that, information seems to get very scarce. The Linux driver operates it by sending messages to the firmware. This would be a lot more tricky than just sending commands to an iic device from userland and beyond my hacking skills.

If it is i2c rather than some n-channel FET, then you have a few options:
1. Look on the design specifications or data sheet for the address of the i2c.
2. Build an i2c scanner using an arduino. This will scan for the address on the bus.

Once you have the address it's trivial to program i2c.There's lots of examples of how to do this out in the internet.

MJ