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Comment by tambourine_man | Hacker News Reader

> This sleek black box can be had for $40-75

That’s not my kind of thing, nor do I have the experience, but at that price, wouldn’t you be better off using a Raspberry Pi (or similar) to control the fans, place thermometers, etc?

I understand that having a computer inside a computer is silly, but we are kind of in that rabbit hole anyway. And a GPIO would be more reassuring to me than depending on driver support for one motherboard/usb fan controller.

Just random thoughts

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Your random thought led me to this one:

A Raspberry Pi that plugs into the a PCI slot, which gives it power and exposes a virtual serial port along with an Ethernet port that shows up on the host system and can be used to route packets to the Pi. The Pi, meanwhile, has all of the usual GPIO things and maybe even an external connector to expose GPIO outside of the PC case.

You might alreay know this: there are USB GPIO devices that get you the I/O without having to program a separate CPU. They're used in custom arcade machines, for one example.

I ran a Pihole off the USB port on a router for a while. Then made an ESP32 temperature monitor that got power off the Pi. I’m not sure why, but the parasitic setup made me happy.

No need to give up a PCIe slot. The Raspberry Pi Zero and the RPi 4 have USB On-The-Go support so they can appear to be a serial port, Ethernet port, or other types of devices using the Linux USB Gadget API. It’s even possible to appear as multiple device types at once.

Overview | Turning your Raspberry Pi Zero into a USB Gadget | Adafruit Learning System https://learn.adafruit.com/turning-your-raspberry-pi-zero-in...

A microcontroller like STM32 would be cheaper and use less power for a fan controller, and would boot instantly and never crash.

They do, you know, run software. Software is sometimes kind of hard to get right, which can lead to crashes even in microcontrollers.

Source: worked as an embedded software developer on mostly STM32s for about 7 years. Did see crashes occasionally.

Agreed but definitely must be quite a few orders of magnitude less crashes than a rPi for a fan controller.

Still overkill, Commander Pro uses $10 8051 8-Bit 50MHz with 64KB flash and 8KB ram.

CY8C3246AXI-138 https://www.cypress.com/part/cy8c3246axi-138

CY8C32xxx processors are based around the 8051 but they're actually part of the fairly capable Cypress PSoC 3 line[1]. The PSoC 3 includes an 8501 compatible processor along with a bunch of mixed signal peripherals and a PLD fabric to connect it all.

[1] https://www.cypress.com/products/psoc-3

And even a 7$/ku MCU is complete overkill (assuming that's the real price, not shortage-related, though its lead time is over a year, so the price is probably inflated), because literally any microcontroller with an ADC can easily do this. Around ten years ago I built my own on a tiny AVR, and even that would be an expensive option compared to what you could use instead in a commercial product (<0.5 $/ku ARM MCUs).

I haven't had a fan controller for many years though, because they're quite pointless if you do things right.

CY8C3246 used to be $5-3.75. Cypress chips were always expensive. Ever since I saw them they always cost as much as separate mcu + separate CPLD.

Still overkill. A 555IC, a variable resistor, a thermistor and a few passives is all you need. You could get the BOM for the whole #! down to under a buck.

You probably don't even need a uC at all. If all you need to control is a bunch of PWM devices from software you can use a USB-I2C bridge and a I2C servo controller. Off-the-shelf solution would be something like Adafruit MCP2221A + PCA9685 but you could easily build it yourself for a fraction of the price.

A rpi would probably take around half a minute to boot. I think it would be a pretty bad fan controller.

Do they really take that long? My RockPRO64 boots in about a second...

It doesn't have to run Linux.

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