And to do that, we're going to need to use the Raspberry Pi's I2C bus! What is I2C? The better option is to use the built-in PWM fan controller on the IO Board (pictured above). But it doesn't know the temperature of my Pi, so it can't increase airflow for higher temperatures or turn off the fan when it's under a certain temperature. It lets me turn up and down the fan speed with a little dial. So what are my options? First of all, I could just buy an inline PWM controller, like a Noctua NA-FC1. See this comment on GitHub for more details, and how to control PWM speeds and trigger temperatures. Once that's done, all you'd need to do (if running Pi OS) is add the following line to your /boot/config.txt file: dtoverlay=i2c-fan,emc2301,i2c_csi_dsi If you need that much cooling, that's great, but a lot of times, I don't mind my Pi's CPU getting warmer if it means I can run the fan silent most of the time.Ģ022-05 Update: Recently, a driver for the EMC2301 fan controller was merged into Raspberry Pi's Linux fork, so it will appear in the next release of Raspberry Pi OS. If you plug a fan like that into the CM4 IO Board, it will start running full blast, 24x7. what's I2C, what's PWM, and what's so special about a 4-pin fan connector? I'm glad you asked-this post will answer that and show you how you can control a fan connected to the IO Board, like the quiet Noctua NF-P12 pictured above with my IO Board. It's connected to the Pi's I2C bus using a little PWM chip, the EMC2301.īut wait.

When I initially reviewed the Compute Module 4 IO Board, I briefly mentioned there's a 4-pin fan connector.

Pwm fan controller