Feed/fuse multiple FAN tacho signals into one MBFAN tacho output

[siodor]

Hello fanpico Community

First, thanks to @tjko for making this great project! 😃

Would it be possible to introduce a way to monitor multiple FAN tacho signals from one MBFAN tacho output?

I have the following situation:

• Mainboard with only 1x PWM fan header
• 3 fans (CPU, PSU, HBA) on the fanpico
  • CPU fan (FAN1) follows signal from MBFAN1
  • PSU fan (FAN2) minimum 50% PWM duty cycle, if MBFAN1 asks for more than 50% then ramp up accordingly
  • HBA fan (FAN3) minimum 50% PWM duty cycle, if MBFAN1 asks for more than 50% then ramp up accordingly
  • If any FANx goes below requested RPM then set MBFAN1 tacho output to zero to notify mainboard and shutdown PC

Could this be implemented?

[tjko]

I would think this should be relatively easy to implement in the firmware.

Existing command: CONF:MBFAN:SOURCE

currently support two types of "sources" for the fan signals: FAN and FIXED

I was thinking, perhaps could add couple new types, something like:

• MIN - returns lowest fan speed of 2 or more fans
• MAX - returns fastest fan speed of 2 or more fans
• AVG - returns average fan speed of 2 or more fans

So something like "CONF:MBFAN1:SOURCE MIN,1,2,3" could be used to configure MBFAN1 header to output whatever is the slowest fan speed observed across fans 1 to 3....

[tjko]

@siodor, initial support for "calculated" sources for MBFAN tacho outputs is now checked in (#59).

What you were looking for should now work if you use "min" fan source across your three fans for the MBFAN1 output.
Something like (assuming fans are FAN1, FAN2, FAN3):

conf:mbfan1:source min,1,2,3

While existing CONF:MBFANx:RPMMAP command should allow making MBFAN1 output to output "0 RPM" signal if fan speed is below desired limit...

If you want to test, firmware images are available (for a short time) at: https://github.com/tjko/fanpico/actions/runs/7148029602
(or you can always compile firmware yourself...)

[siodor]

Hello @tjko ,

Wow, thanks for the quick implementation.

I'll give it a go today.

[siodor]

Hello @tjko

I managed to test this over the weekend and it works as suggested with
conf:mbfan1:source min,1,2,3
like a charm

My testing was very simple. I unplugged the fans one by one and the status LED of the PC immediately went red each time.

[tjko]

Thanks for testing. I only tested with two fans, glad to hear it seems to work fine with more fans as well.