PiStackMon, a SBC stack monitor / power delivery modules

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mctom
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PiStackMon, a SBC stack monitor / power delivery modules

Post by mctom »

Hello!

A few months ago I developed a PiStackMon board, an open source SBC monitor if anyone happens to build a SBC cluster at home. :)
Its principal purpose is to deliver power to many stacked SBCs easily, adding an extra bulk capacitor, power switch and a polyfuse. As a bonus, it offers a clear LED matrix displaying real time stats. Over time I added even more features, such as SPI, I2C and 1-Wire pinouts, opto-isolated outputs and whatnot. All that is optional and depends how you build your board.

https://github.com/tomek-szczesny/pistackmon
PiStackMon
PiStackMon
175585808_307191184125634_9007715176935834939_n.jpg (530.09 KiB) Viewed 546 times
Sadly, my SBC stack consists of various RasPi boards off the second hand market, that I bought and fixed myself. Apparently there are no broken Odroids out there. :) I also build an XU4 stack right next to it, but sadly it has incompatible connector, both physically and in terms of voltage levels. Also I can't find angled 30-pin, 2-mm female connectors anywhere, I doubt those even exist.

Recently a friend of mine voiced his interest in providing compatibility of this board with Odroid C4 stack he's about to build. I am more than happy to do that, but I do not have this model at hand for testing. As far as I can tell, PiStackMon should also work with C2, N2 and N2+. I am a proud owner of N2+ and could try it out if it wasn't permanently screwed under my desk, but I think I ought to try it somehow anyway.

Anyway, this enormous plug is not the point of this post. I'd like to ask for help with determining the memory maps / addresses of GPIO pheripherals for aforementioned boards, so I could add these to my code.
I wouldn't dare to ask anyone for helping me with testing this. Nevertheless, if anyone is interested and lives in Europe, I could send some boards to play with. Outside of Europe, I guess it's cheaper to actually build them yourselves.

Also, if anyone has any idea why Odroid would not work with PiStackMon, I'd be happy to hear your concerns. For example, I'm not sure if N2 / N2+ can be powered from 5V pins on GPIO header.
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Re: PiStackMon, a SBC stack monitor / power delivery modules

Post by joerg »

It's looking awesome! Sadly the N2 / N2+ and C4 cannot be powered via GPIO header. They need to be powered by the power connector with > 5.5V (as I remember correct). That's why I built my C4 Car Interface board the way I built.
I wish Hardkernel could make again a board C4 like, but with option to power via GPIO like C1 / C2.

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Re: PiStackMon, a SBC stack monitor / power delivery modules

Post by mctom »

Thanks! :)

I think my N2+ runs off 12V, but I can't think of anything that actually needs more than 3V3 on board.
I wonder why C4 can't work powered directly via GPIO.

Oh, I see.. Powering the board via VCC5V might not work. Perhaps it would, if there was an easy way to bridge VCC5V with DC_JACK, and disable JW5057?

EDIT: On second thought, no need to disable that Buck converter.
It seems there is unpopulated J3 header connected directly to DC_JACK, and 7-pin GPIO right next to it, that has VCC5V on its pin 3. A short wire between these two would do the trick, I believe. However it would surely lose all protection against power supply voltages above 5V.

EDIT2: Apparently the Amlogic chip is connected to VCC5V for some LDO action.
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Re: PiStackMon, a SBC stack monitor / power delivery modules

Post by mctom »

I might get a substantial surplus of XU4s (10+ units) so I think it's the high time to create a revision that supports XU4.

Surprisingly, the biggest challenge is to get 90 deg angled, 30-pin female headers with 2mm pitch, that would fit XU4.
Any help finding those anywhere on the market would be deeply appreciated. So far I have never seen anything like it.

EDIT: Huh. What do you know. I guess I wasn't looking hard enough.
https://pl.aliexpress.com/item/4001286548060.html
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Re: PiStackMon, a SBC stack monitor / power delivery modules

Post by mad_ady »

Don't forget a level shifter! XU4 is 1.8V sadly...

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Re: PiStackMon, a SBC stack monitor / power delivery modules

Post by mctom »

Yep, that's the main reason for redesigning the board just for XU4.
This would actually be better to find LED driver that works with 1.8V logic in the first place. Level shifter is bulky and hard to route in such tight space and cheap JLC technology. ;)
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Re: PiStackMon, a SBC stack monitor / power delivery modules

Post by mad_ady »

So you want to use leds to drop the voltage instead of a resistor divider?

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Re: PiStackMon, a SBC stack monitor / power delivery modules

Post by mctom »

Noooo, of course not. :D

In the original design, there's a 16x constant current LED driver that is powered from 5V, but accepts 3.3V logic, which makes it compatible with "RasPi format". LED driver listens to SBC via bit-banged interface similar to SPI.
LEDs themselves are also powered from 5V, with current regulated by the driver. It is a feature of these chips.
So, the only change necessary would be to find a LED driver that understands 1.8V logic, or to translate necessary logic signals to 3.3V. With just three of them, perhaps 3x npn transistor would be enough instead of an n-bit level shifter, but I'll look into that, in terms of surface area and cost.
Maybe even a dirty hacky "reverse resistor divider" would be sufficient to shift the voltage into appropriate levels.

The remaining features would change as pin count and layout changes, but since I designed them from discrete components it should be easy enough.
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Re: PiStackMon, a SBC stack monitor / power delivery modules

Post by mctom »

I found a cheap, single channel unidirectional level shifter.
https://pl.mouser.com/ProductDetail/Tex ... RrSQ%3D%3D

2mm x 1.2mm... Clearly they do not consider my eyesight and dexterity will only get worse from now on. Hmph.

EDIT:
Aha, and here is a 36 channel LED driver that accepts 1.8V logic! And does PWM on its own, oooh..
https://pl.mouser.com/datasheet/2/198/I ... 949575.pdf
It talks I2C, though, and I prefer bitbanging my interfaces (it's usually faster). So some measures will be necessary to protect XU4 from this chip talking back.
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Re: PiStackMon, a SBC stack monitor / power delivery modules

Post by mctom »

I am planning to get rid of my stack of Pis, as the market says they're worth more monies these days than I think they should be.
And I prefer XU4s. They are just... cool.

This is why I'm willing to give away a few PiStackMon boards to the owners of Odroid C series. Most of the board I've build have only monitoring options (pretty LED resource stats).
The only thing I'm asking in return is to help me test compatibility with Odroid C series. Sadly I do not have any of these.
PM me if you are interested! :)
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Re: PiStackMon, a SBC stack monitor / power delivery modules

Post by mctom »

This is the day, I thought, when I will finally unscrew my N2+ from the bottom of my desk to provide PiStackMon support for it.

Well, it turns out I can't, in the most unexpected way. The heatsink is in the way. :cry:
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Re: PiStackMon, a SBC stack monitor / power delivery modules

Post by tobetter »

@mctom, Ouch!! :oops:

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Re: PiStackMon, a SBC stack monitor / power delivery modules

Post by mad_ady »

HK sold GPIO risers for XU4. Perhaps something similar exists for regular GPIOs.

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Re: PiStackMon, a SBC stack monitor / power delivery modules

Post by mctom »

Ha, this is correct. I have just used another angled connector as a riser. IT seems to work, at least got power.

Now onto coding, hm. Memory maps and stuff..
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Re: PiStackMon, a SBC stack monitor / power delivery modules

Post by mctom »

Aaand here it is! Let's celebrate tobetter style! :D

ODROID N2(+) officially supported!

The temperature indicator is useless on N2+, as temperatures above 50 don't really happen to me ever, but it works. I reached 40-something with stress -c 6, which is indicated as barely glowing 50 deg mark.

Pardon crappy photos, my girl was already asleep ;)
Picture shows stress -m 8 to confirm the RAM indicator works as well.
IMG_20211125_220938.jpg
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odroid (Fri Nov 26, 2021 9:14 am) • tobetter (Fri Nov 26, 2021 9:52 am)
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Re: PiStackMon, a SBC stack monitor / power delivery modules

Post by mad_ady »

Congrats!
You can test the temperature with a hair dryer
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tobetter (Fri Nov 26, 2021 3:07 pm)

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Re: PiStackMon, a SBC stack monitor / power delivery modules

Post by mctom »

I know that was a joke, bu that test is not necessary after all.
All I need to check is if I can drive 3 pins correctly (which is quite easy to test - see if it does anyhting), and if Odroid has the same CPU temperature location in the filesystem as Raspi, which it does. The rest is implemented in pretty much universal manner.
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