ATXRaspi and ATX PSU

[silver]

Hi,

I am planning to power a Raspberry Pi project using an ATX PSU. For that, I need an interface between the ATX PSU and Raspberry Pi. I am thinking ATXRaspi might be the solution that I need. I just need some answers that I didn't find on your web page.

When exactly will ATXRaspi turn off the power supply to the Pi? It's not told on your web page but I am assuming that it will happen once the Pi sets zero the same GPIO pin that tells ATXRAspi that the Pi has booted. Am I correct about that?

If that's the case, I think I should be able to do the following configuration:
1. Power ATXRaspi from the 5V stand-by line of the ATX PSU.
2. Use the ATXRaspi power output not as power source for the Pi but as control signal connected to the /enable pin of the ATX PSU connector.
3. Power the Pi from the ATX PSU 5V line and also power any hardware like a harddrive from the same ATX PSU.

Do you agree that such a configuration should work or is there something about the internals of ATXRaspi that I am missing? I know I will need to do some custom wiring myself and also to implement logical inverter for the ATXRaspi power output as the ATX PSU /enable is active-low, but those are not a problem for me. What counts is whether I have understood the functionality of ATXRaspi right.

[Felix]

You are correct. As the Pi shuts down it will pull down the signal back into ATXRaspi which then waits a few more seconds before it cuts power.
So you should be able to do what you said, BTW interesting idea. I would test on a small scale on a breadboard without a Pi to avoid any damage. Just connect a light load like a bunch of LEDs or a motor instead of the Pi. Then simulate the bootOK and shutdown scenarios using a wire to pull those signals to 5V and GND respectively.
FWIW ... how much power does your hard drive need? Wondering if ATXRaspi could handle it ...

[Felix]

Actually never mind, I think any HDD is at least a few watts which will double the consumption. The Pi is rated at 700mA which is more than normal USB anyway, so when you add a HDD that could easily double that.

[silver]

Thanks for good news!

I will need the ATX PSU anyway as the hard-drive I am going to use is a 3,5" model and thus needs 12V.

What I am actually doing is replacing Athlon-level PC hardware with the Pi in a HTPC that is only used to play .flac files. And, in addition to that, I am going to "replace" onboard audio with a proper DAC.

[Felix]

Cool project, please consider sharing your progress in here, I'm sure it will make a great project and if it's well documented and includes pictures/video I can post it on my blog!