Pin-out of H4's 24-pin Peripheral Expansion Header? (Front panel USB?)

Post Reply
mattbot
Posts: 125
Joined: Fri Jan 08, 2016 10:35 am
languages_spoken: english
ODROIDs: N2+
Has thanked: 64 times
Been thanked: 12 times
Contact:

Pin-out of H4's 24-pin Peripheral Expansion Header? (Front panel USB?)

Post by mattbot »

I'm having trouble finding a full map of the pins in the H4's 24-pin header.

Right now, I guess the main thing I want to know is whether any of the pins are for USB ports, since I bought the mini-ITX adapter and I'm wondering if there's any way to connect the case's front panel USB ports internally. According to this diagram, it certainly looks that way:

Image
Last edited by mattbot on Mon Jul 08, 2024 1:30 am, edited 1 time in total.

User avatar
mctom
Posts: 4330
Joined: Wed Nov 11, 2020 4:44 am
languages_spoken: english, polski
ODROIDs: XU4, M1, H3+, SP3, N2L, M1S, N2
Location: Gdańsk, Poland
Has thanked: 642 times
Been thanked: 875 times
Contact:

Re: Pin-out of H4's 24-pin Peripheral Expansion Header?

Post by mctom »

These users thanked the author mctom for the post:
mattbot (Mon Jul 08, 2024 12:39 am)
Punk ain't no religious cult, punk means thinking for yourself!
OpenUPS
PiStackMon

mattbot
Posts: 125
Joined: Fri Jan 08, 2016 10:35 am
languages_spoken: english
ODROIDs: N2+
Has thanked: 64 times
Been thanked: 12 times
Contact:

Re: Pin-out of H4's 24-pin Peripheral Expansion Header?

Post by mattbot »

Thanks, but I really wish the mini-ITX adapter kit would include a breakout board that makes it easier to connect case front panel connectors. For one thing, it's annoying to have only a single +5 VDC power pin.

Since the mini-ITX extension board seems to be fabricated like a PCB, maybe the breakout could've simply been incorporated into it and you just connect a ribbon cable between them. Perhaps this is an idea worth considering for the H5 generation.

BTW, I've noticed USB front panel connectors including two ground pins, with one of them being labelled S-GND and specified for "Over Current". Should I just connect that up to any of the ground pins in the block? Should it go directly to the case?

User avatar
mctom
Posts: 4330
Joined: Wed Nov 11, 2020 4:44 am
languages_spoken: english, polski
ODROIDs: XU4, M1, H3+, SP3, N2L, M1S, N2
Location: Gdańsk, Poland
Has thanked: 642 times
Been thanked: 875 times
Contact:

Re: Pin-out of H4's 24-pin Peripheral Expansion Header? (Front panel USB?)

Post by mctom »

That's probably Signal Ground, it can be connected to GND on the header.
These users thanked the author mctom for the post:
mattbot (Mon Jul 08, 2024 6:50 am)
Punk ain't no religious cult, punk means thinking for yourself!
OpenUPS
PiStackMon

mattbot
Posts: 125
Joined: Fri Jan 08, 2016 10:35 am
languages_spoken: english
ODROIDs: N2+
Has thanked: 64 times
Been thanked: 12 times
Contact:

Re: Pin-out of H4's 24-pin Peripheral Expansion Header? (Front panel USB?)

Post by mattbot »

mctom wrote:
Mon Jul 08, 2024 6:00 am
That's probably Signal Ground, it can be connected to GND on the header.
You think that's more likely than "Shield Ground"? I'm pretty clueless about this stuff, but I think that would be more consistent with over-current.

Ah, according to this, it's indeed shield ground: https://electronics.stackexchange.com/q ... -usb-cable

That better explains why only one is shared between two USB ports.

User avatar
mctom
Posts: 4330
Joined: Wed Nov 11, 2020 4:44 am
languages_spoken: english, polski
ODROIDs: XU4, M1, H3+, SP3, N2L, M1S, N2
Location: Gdańsk, Poland
Has thanked: 642 times
Been thanked: 875 times
Contact:

Re: Pin-out of H4's 24-pin Peripheral Expansion Header? (Front panel USB?)

Post by mctom »

Doesn't matter, it's still Ground, so you know where to plug it. ;)
Punk ain't no religious cult, punk means thinking for yourself!
OpenUPS
PiStackMon

mattbot
Posts: 125
Joined: Fri Jan 08, 2016 10:35 am
languages_spoken: english
ODROIDs: N2+
Has thanked: 64 times
Been thanked: 12 times
Contact:

Re: Pin-out of H4's 24-pin Peripheral Expansion Header? (Front panel USB?)

Post by mattbot »

mctom wrote:
Mon Jul 08, 2024 7:12 am
Doesn't matter, it's still Ground, so you know where to plug it. ;)
Thanks for the reassurance and sorry to be a pain, but they broke it out as a separate pin than ground, so I think my uncertainty isn't unreasonable.

Given that we now know it's the shield ground wire, would there be any sense in running it to the case? Does that amount to the same thing? Am I just splitting hairs?

In fact, some places seem to suggest you can leave it disconnected, which I'm sure is normally fine, but I guess the key question is: then what happens when somebody zaps it with an ESD (spark)?

User avatar
mctom
Posts: 4330
Joined: Wed Nov 11, 2020 4:44 am
languages_spoken: english, polski
ODROIDs: XU4, M1, H3+, SP3, N2L, M1S, N2
Location: Gdańsk, Poland
Has thanked: 642 times
Been thanked: 875 times
Contact:

Re: Pin-out of H4's 24-pin Peripheral Expansion Header? (Front panel USB?)

Post by mctom »

Very well..

ESD happens when you touch or are very close to a conductive surface, and happen to be charged up, mostly due to your poor fashion choices. ;)
As a user you have no chance of touching a USB cable shield.

This shield is for EMC protection, which stands for Electromagnetic Compatibility. Each piece of equipment must not transmit more than certain amount of radiated energy, and must be immune to similar conditions itself. Every time you're dealing with changing voltage or current, energy is radiated. The faster the data rate, the more of a problem it is.
EMC is a long forgotten chapter of black magic. Nobody ever knows how to do it properly, because managing invisible rays that are hard to measure is exactly what it sounds like.

You can connect it to GND on either end, or both, since there is a dedicated parallel GND wire anyway, and providing alternative GND path won't do any damage.

There is no rule that metal cases are always better (because shielding) and that a ceremony of connecting grounds in a sophisticated manner grants protection of ESD gods.
Sometimes cases are deliberately made of non-conductive materials exactly to protect against ESD, or to provide mandatory protection of a user against AC grid voltage (especially in Class II devices).
The worst, however, is a floating, flat piece of metal. Floating means unconnected to anything. When zapped with ESD, it acts as an antenna surface that transmits an almost parallel EM wave.
I demonstrated this 2 jobs ago, when I was resetting the flagship product of the company by zapping a spoon with a piezo cigarette lighter, standing 1m away. Spoon is even better because it's almost like a parabolic satellite dish.

However, one can argue that grounded metal shielding is always beneficial against EMC. Again, that's black magic. Since none of us have sufficient equipment to measure all that, it's too easy to fall victim of the placebo effect (see the booming audiophile equipment market, lol). Audiophiles buy gold-plated AC wires for their CD players and sincerely believe it makes their systems sound better. The can hear the difference, even though there is none. Similarly, it's too easy to notice a visible EMC improvement without any means of measuring these effects in the first place.

The healthiest approach is to act on the troubles that may arise in your target environment, and not trying to avoid them beforehand, because predicting any of that is literally out of reach of human knowledge and technology combined.
The biggest problems in industrial environment isn't radiated EMC anyway, but ground loops and conducted noise everywhere.
These users thanked the author mctom for the post:
mattbot (Mon Jul 08, 2024 11:27 pm)
Punk ain't no religious cult, punk means thinking for yourself!
OpenUPS
PiStackMon

mattbot
Posts: 125
Joined: Fri Jan 08, 2016 10:35 am
languages_spoken: english
ODROIDs: N2+
Has thanked: 64 times
Been thanked: 12 times
Contact:

Re: Pin-out of H4's 24-pin Peripheral Expansion Header? (Front panel USB?)

Post by mattbot »

mctom wrote:
Mon Jul 08, 2024 6:16 pm
You can connect it to GND on either end, or both, since there is a dedicated parallel GND wire anyway, and providing alternative GND path won't do any damage.
Okay, I'll connect it to ground. I only control one end, anyhow.

Thanks for the interesting discussion!

Post Reply

Return to “Hardware and peripherals”

Who is online

Users browsing this forum: No registered users and 6 guests