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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 12:31 am

solar3000 wrote:
Thu Jun 27, 2019 12:17 am
What functions does the USB C connector provide besides 5 volts?
Future proofing.

For the foreseeable future, this connector will become as common as dirt, probably even more than micro USB.

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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 12:34 am

chithanh wrote:
Wed Jun 26, 2019 9:16 pm
W. H. Heydt wrote:
Wed Jun 26, 2019 5:38 pm
There is a major, major problem with your contention with regard to the USB-C connector. Its internal connection is to the "legacy" SoC USB port...which is USB 2.
That was a choice by the board designer. Changing the board layout and connecting USB-C to USB3 would be possible. But as the BCM2711 appears to not support DisplayPort (see above), we will never see display via USB-C in this generation, so routing one of the two USB 3 ports via the USB-C connector would be a waste.
The USB 3 ports are connected to the one and only PCIe lane in the SoC, so connecting the USB C connector to that would be running traces all over the place. Not a good idea. The SoC has retained the "legacy" USB 2 port on the SoC. On prior Pis, that went to a USB/Ethernet hub chip. On the Pi4B, that function is, as noted, on the PCIe lane. So rather than leaving the USB 2 connection unused, it is connected to the USB C port. It's not so much "Wow! We can give some USB 2 functions to the USB C connector" as "Hmmm... We've got an otherwise unused USB 2 port...at least it can be hooked up to the USB C power connector." This way, one of the additional features is an OTG capability--a first for a B-series Pi. Would you rather that USB 2 port been left dangling and unconnected?

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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 12:36 am

solar3000 wrote:
Thu Jun 27, 2019 12:17 am
What functions does the USB C connector provide besides 5 volts?
On the Pi4B it is actually a functional USB 2 port, with OTG capability.

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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 12:58 am

solar3000 wrote:
Thu Jun 27, 2019 12:17 am
jamesh wrote:
Wed Jun 26, 2019 11:56 am
There's no facility in the SoC for display over USB, so that is a non-starter.

With regards to dual height connectors, they would apply too much torque to the attachment point

The micro-HDMI are the right size, are robust (I've been plugging in and out for months with no problems), cheap, and we now sell very cost effective cables (or use an adapter) to go with them.

I doubt we will be moving back to the larger connectors on dual capable devices.

What functions does the USB C connector provide besides 5 volts?
On a Pi? OTG


Im happy enough with the Pi4 as is.
It was certainly a shock to see two connectors, especially one I have never heard of before, but it's not impossible to adapt and simply accept it for what it is.

My personal opinions about the exact connector chosen aside, I think this is a good decision for the Pi.
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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 1:03 am

Imperf3kt wrote:
Thu Jun 27, 2019 12:58 am
My personal opinions about the exact connector chosen aside, I think this is a good decision for the Pi.
It occurs to me that, by being used on the Pi4B--which will undoubtedly sell in the millions if not tens of millions, it may make microHDMI pretty much an SBC standard.

Now if my preferred supplier would just suddenly start stocking microHDMI to DVI cables....

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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 1:37 am

Cool that USB-C has USB 2.0 and OTG functionality. I had assumed it was only a power port. Image

W. H. Heydt wrote:
Thu Jun 27, 2019 1:03 am
Now if my preferred supplier would just suddenly start stocking microHDMI to DVI cables....
HDMI-DVI.jpg
HDMI-DVI.jpg (16.81 KiB) Viewed 2018 times
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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 2:19 am

HawaiianPi wrote:
Thu Jun 27, 2019 1:37 am
Cool that USB-C has USB 2.0 and OTG functionality. I had assumed it was only a power port. Image
It helps to read moderator comments carefully. All sorts of interesting things pop up. Like the VC6 having 35 address lines.
W. H. Heydt wrote:
Thu Jun 27, 2019 1:03 am
Now if my preferred supplier would just suddenly start stocking microHDMI to DVI cables....
HDMI-DVI.jpg
I have some of those. I'll probably get more.

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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 2:24 am

HawaiianPi wrote:
Thu Jun 27, 2019 1:37 am
W. H. Heydt wrote:
Thu Jun 27, 2019 1:03 am
Now if my preferred supplier would just suddenly start stocking microHDMI to DVI cables....
HDMI-DVI.jpg
That's mini hdmi, not quite compatible with micro hdmi
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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 2:46 am

Imperf3kt wrote:
Thu Jun 27, 2019 2:24 am
HawaiianPi wrote:
Thu Jun 27, 2019 1:37 am
W. H. Heydt wrote:
Thu Jun 27, 2019 1:03 am
Now if my preferred supplier would just suddenly start stocking microHDMI to DVI cables....
HDMI-DVI.jpg
That's mini hdmi, not quite compatible with micro hdmi
You sure? Looks like a full sized HDMI to me, and that's what the ones I have are.

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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 3:11 am

Looking again, it is full size hdmi.

So the suggestion is to use an adaptor on either end?
Where I live, adaptors like that are $30 each. Plus the cable, another $15, bringing the total to $75 (that's AUD also, not USD)
That wouldn't be my preferred choice...
Last edited by Imperf3kt on Thu Jun 27, 2019 5:10 am, edited 1 time in total.
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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 4:57 am

I wish there was an official micro hdmi to DVI-D cable for those of us with cheap monitors!

I can get one on Ebay for £3 but will it work?...
Yes, tested on 1920x1080 and 1280x1024.
Will it do 4K? No idea don't have anything to test it on.
Are there 4K DVI screens?

MicroHMDI adapter was only $2.80 AUD, but too wide to use two of them.
Get the official cables as they are rated for 4K and fit.

MicroUSB to USB-C also $2.80, so tiny I got two in case one goes missing.

My biggest beef is now I need to clean up my desk to make room for two monitors :oops:
But I can probably save space by getting rid of the old boat anchor PC.
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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 8:03 am

During the AMA with Eben Upton at Tom's Hardware he answered some questions about the display output posted by me and others.

Summary:
  • Dual deck / stacked HDMI connectors was considered, but rejected due to Torque (that was mentioned by jamesh already), EMC issues, and increased Z height
  • Upright HDMI connectors were not considered as far as he is aware
  • Display output via USB Type-C would have required additional protection components
  • Bringing along a Micro HDMI adapter everywhere you take the Pi is not a significant burden normally, though he gets the point that for certain users Micro HDMI can be a more serious problem
  • He still thinks that the current board layout with dual Micro HDMI was the right decision, and tells us to not expect that to change any time soon
W. H. Heydt wrote:
Thu Jun 27, 2019 12:34 am
The USB 3 ports are connected to the one and only PCIe lane in the SoC, so connecting the USB C connector to that would be running traces all over the place. Not a good idea.
The placement of the USB ports and the USB3 host controller was a choice by the board designer too. But even so, trace length would not be that much of a problem I guess.
W. H. Heydt wrote:
Thu Jun 27, 2019 1:03 am
It occurs to me that, by being used on the Pi4B--which will undoubtedly sell in the millions if not tens of millions, it may make microHDMI pretty much an SBC standard.

Now if my preferred supplier would just suddenly start stocking microHDMI to DVI cables....
I don't expect that. Both Micro HDMI and DVI are more on the legacy side of things.
Gavinmc42 wrote:
Thu Jun 27, 2019 4:57 am
Will it do 4K? No idea don't have anything to test it on.
Are there 4K DVI screens?
No, with (Micro)HDMI->DVI passive adapters you are effectively limited to 1080p60.

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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 9:17 am

So on one hand you want large compatible connectors so you don't have to carry around adaptors and on the other you want future USB-C/Displayport capability that would require most people to buy adaptors. I don't get it ?
Very few people I know actually have DP displays or have usb-c most are still on DVI/HDMI and u-usb. I'm in the uk working in Education.

USB-C with a bulk HDMI adaptor/Charger works nicely on the Nintendo Switch though, i'll give it that.

As with others
My Tablets, a Laptop and iirc two of my camera all have uHDMI and have done for a long time. oddly miniHDMI was the one I hadn't seen used a lot when they released that.

But we got over it and just used what was there.
Also I and many others do use the HDMI out on the Zero series.
I do however have far too many OTG/HDMI adaptors now from the Zero's that came with them. To many cases as well. :lol:

I wonder if they'll (someone) will make 'lids' for the Pi4 case. A camera hole or a cut out for the SenseHAT display/joystick.

Anyway, I like it, the connectors are not bulky :-)

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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 9:22 am

Following this thread now for a while I need ro make a comment as well: people should be happy that it's now possible and super easy to connect two displays to a Pi, have 4k resolution (@60Hz) and stop complaining on a connector size.
Pretty sure everbody complaining here can design a Pi better, with more features, bigger connector on a stamp size PCB

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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 9:34 am

I have never seen a USB-C input monitor in the wild. I know they exist, I've just looked it up and Ebuyer sell them. Not cheap for a decent one.

But they are still pretty rare, and one of the selling points on the Pi is that it can connect to TV's which are almost exclusively HDMI.

So I do not think USB-C for video is anywhere near the mainstream enough for it to be used on the Pi (even if it were technically feasible, which I doubt at this stage)

We are happy with uHDMI. The leads might be a bit rarer, but we sell our own at sensible prices for those that need them, and adapters are very cheap from Ebay.
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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 10:43 am

solar3000 wrote:
Thu Jun 27, 2019 12:17 am
jamesh wrote:
Wed Jun 26, 2019 11:56 am
There's no facility in the SoC for display over USB, so that is a non-starter.

With regards to dual height connectors, they would apply too much torque to the attachment point

The micro-HDMI are the right size, are robust (I've been plugging in and out for months with no problems), cheap, and we now sell very cost effective cables (or use an adapter) to go with them.

I doubt we will be moving back to the larger connectors on dual capable devices.

What functions does the USB C connector provide besides 5 volts?
It's a USB 2.0 OTG port - so you can power it via that port whilst simultaneously connecting USB devices - including device mode.

Previously the Pi Zero has supported device mode, which has been pretty useful.

It allows the Pi to be powered and connected to a host computer and appear as an Ethernet device (providing a network connection between the two machines), Mass Storage Device, Keyboard, Mouse etc. It also allows the USB C port to connect to external USB deices in the same way as the USB 2.0 Type A ports.

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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 11:07 am

Imperf3kt wrote:
Thu Jun 27, 2019 3:11 am
Looking again, it is full size hdmi.

So the suggestion is to use an adaptor on either end?
Where I live, adaptors like that are $30 each. Plus the cable, another $15, bringing the total to $75 (that's AUD also, not USD)
That wouldn't be my preferred choice...
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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 12:06 pm

6by9 wrote:
Wed Jun 26, 2019 12:08 pm
People complained over the mini-HDMI on the PiZero too, but again it's not that big a deal.
I will not complain about the zero, nor about the 4. But if you already used the mini-hdmi on the raspberry why would you use the micro-hdmi on the raspberry 4?

If micro-hdmi is better, Why was not used on the zero?

I understand the need for a smaller conector, but I cannot get why don't you use the same smaller conector.

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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 12:51 pm

jokinc wrote:
Thu Jun 27, 2019 12:06 pm
6by9 wrote:
Wed Jun 26, 2019 12:08 pm
People complained over the mini-HDMI on the PiZero too, but again it's not that big a deal.
I will not complain about the zero, nor about the 4. But if you already used the mini-hdmi on the raspberry why would you use the micro-hdmi on the raspberry 4?

If micro-hdmi is better, Why was not used on the zero?

I understand the need for a smaller conector, but I cannot get why don't you use the same smaller conector.
The MicroHDMI is smaller (half the size) which is why it is used on the Pi4 - space was very limited. IIRC, at the time of the Zero launch, mini-HDMI was cheaper so that is why it was used.
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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 2:12 pm

W. H. Heydt wrote:
Thu Jun 27, 2019 12:36 am
solar3000 wrote:
Thu Jun 27, 2019 12:17 am
What functions does the USB C connector provide besides 5 volts?
On the Pi4B it is actually a functional USB 2 port, with OTG capability.

that would make a good dock, right doc?
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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 2:23 pm

noggin wrote:
Thu Jun 27, 2019 10:43 am
solar3000 wrote:
Thu Jun 27, 2019 12:17 am
jamesh wrote:
Wed Jun 26, 2019 11:56 am
There's no facility in the SoC for display over USB, so that is a non-starter.

With regards to dual height connectors, they would apply too much torque to the attachment point

The micro-HDMI are the right size, are robust (I've been plugging in and out for months with no problems), cheap, and we now sell very cost effective cables (or use an adapter) to go with them.

I doubt we will be moving back to the larger connectors on dual capable devices.

What functions does the USB C connector provide besides 5 volts?
It's a USB 2.0 OTG port - so you can power it via that port whilst simultaneously connecting USB devices - including device mode.

Previously the Pi Zero has supported device mode, which has been pretty useful.

It allows the Pi to be powered and connected to a host computer and appear as an Ethernet device (providing a network connection between the two machines), Mass Storage Device, Keyboard, Mouse etc. It also allows the USB C port to connect to external USB deices in the same way as the USB 2.0 Type A ports.

I keep a zerow in my pocket all the time - doesn't everyone. I always run out of ports.
I didn't know the 0 had two OTGs - or did I forget.
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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 2:41 pm

jamesh wrote:
Thu Jun 27, 2019 12:51 pm
The MicroHDMI is smaller (half the size) which is why it is used on the Pi4 - space was very limited. IIRC, at the time of the Zero launch, mini-HDMI was cheaper so that is why it was used.
well, I hope that for the next zero you converge on one kind, I keep loosing my adapters, and this time I have bought several micro-hdmi to hdmi cables.

Good and unexpect update anyway, and in my case it was just when I had to buy several raspberrys so perfectly timed. Waiting now for some providers to update with support to the multiple monitors and other goodies.

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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 3:43 pm

solar3000 wrote:
Thu Jun 27, 2019 2:23 pm
I keep a zerow in my pocket all the time - doesn't everyone. I always run out of ports.
I didn't know the 0 had two OTGs - or did I forget.
The Pi0/Pi0W have only one actual USB port. The other connector is power only. The reason that the Pi4B USB-C connector *can* also be a USB port is because the "normal" USB ports aren't using the SoC's native USB 2 port. So rather than letting it go unused (which is starting to look like it might have be a good decision, what with all the confusion going on), the data lines were routed to the USB-C "power" connector.

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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 3:52 pm

jokinc wrote:
Thu Jun 27, 2019 2:41 pm
well, I hope that for the next zero you converge on one kind, I keep loosing my adapters, and this time I have bought several micro-hdmi to hdmi cables.
I seriously doubt that the Pi0/Pi0W will change connectors until there is a major board revision, such as to upgrade the SoC. I've commented at length, elsewhere, on the issues around to that, but the big one is...finding a suitable SoC that will work and is cheap enough.

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Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

Thu Jun 27, 2019 9:49 pm

bensimmo wrote:
Thu Jun 27, 2019 9:17 am
So on one hand you want large compatible connectors so you don't have to carry around adaptors and on the other you want future USB-C/Displayport capability that would require most people to buy adaptors. I don't get it ?
I think you misunderstand.

I would like to have at least one full-size HDMI connector on the Pi. But the PCB is small; next to one full-size horizontal HDMI connector there is no space for another one. That means for enabling a second display, the following options exist:
  • Use two Micro HDMI connectors and use adapters. This option was chosen.
  • Use dual-deck (stacked) HDMI connectors. This option was rejected due to torque, EMC issues, and Z height.
  • Use two upright (vertical) HDMI connectors. This option was not even considered.
  • Use the USB-C connector for the second display. Presumably, this was not feasible with the BCM2711, and too expensive anyway.
For the second display, it is totally ok to use something obscure or not so popular, because in case you don't have the special cable at hand, your Pi will gracefully degrade to a single monitor system. USB-C with DisplayPort would be great because that is the future, but any other option is fine too.

The reason I detailed in a previous post:
chithanh wrote:
Wed Jun 26, 2019 9:16 pm
One of the really, really great things about the Raspberry Pi 1-3 is that you could take the bare board basically any place in the world that has electricity, hook it up using technology that is omnipresent (microUSB for power, HDMI for display, SD/microSD cards for storage, USB for keyboard/mouse) and get going.
If your HDMI cable is lost or broken or you forget to bring it along, then you can walk into literally any place that sells electronics, worldwide, and buy replacement. Or ask your neighbour to borrow you one.
In the same situation with Micro HDMI, that is only true for larger stores that carry such speciality equipment. Which is totally not an issue as long as you live in an urban area in a developed country. Which I guess is what >90% of Raspberry Pi customers do, and which is probably why the compromise of this ability is not seen as problem by the Raspberry Pi engineers.
bensimmo wrote:
Thu Jun 27, 2019 9:17 am
My Tablets, a Laptop and iirc two of my camera all have uHDMI and have done for a long time.
Even in its heyday, Micro HDMI was more of a niche connector. It saw limited use in the areas which you mentioned, but it was never even close to ubiquity.
jamesh wrote:
Thu Jun 27, 2019 9:34 am
I have never seen a USB-C input monitor in the wild. I know they exist, I've just looked it up and Ebuyer sell them. Not cheap for a decent one.

But they are still pretty rare, and one of the selling points on the Pi is that it can connect to TV's which are almost exclusively HDMI.

So I do not think USB-C for video is anywhere near the mainstream enough for it to be used on the Pi (even if it were technically feasible, which I doubt at this stage)
Again, I do not advocate to remove HDMI. On the contrary, it wish for at least one full-size HDMI port. Because then you can connect to TVs and you can use cables which are sold basically everywhere.

Whether the second display output is USB-C, HDMI, Micro HDMI or whatever else is not that important. Sure, USB-C would be great because that is now reaching reasonably priced monitors (e.g. Lenovo P24h-10 for ~230 EUR) and it seems to be the direction that modern computing is moving to.

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