RafaPolit
Posts: 4
Joined: Wed Apr 04, 2018 4:35 am

Rpi3 B + Official Touchscreen + Official Power Supply (revisited)

Wed Apr 04, 2018 5:18 am

Good evening friends.

This is my first post, and I have read several similar posts without a truly satisfying answer. So even though this has been **mostly** answered many, many times, I will repeat this in the sake of getting a clear answer:

- I have the Screen attached to the adapter board correctly
- I have the board attached to the RPi3 B, as per the guide as follows: the DSI ribbon flat cable to the adapter board and Pi, and the +5 and ground jumper cables to the GPIO in the Pi.
- I have an OFFICIAL 5.1v 2.5A Power Supply (not any other cheap, or kit supply, the official one!)

Things mostly work.

Scenarios:
- If I power the system with the power inserted into the adapter board PWR IN (as per the instructions), I get a recurrent yellow 'thunder' on the right hand top side of the screen
- If I power the system (as NOT recommended in the instructions) directly to the Pi Power in, things work perfectly, no yellow bolt on sight.

Now, I am worried as, even though this works, the instructions clearly read:
"Do not power the setup via the Pi's micro-USB port: the input polyfuse's maximum current rating will be exceeded as the display consumes approximately 400mA".

What is happening? Why is the 'recommended' setup (and everything with the official components!) not working?

I would prefer not to use separate power supplies. But if that would be the case, do I need to unplug the jumper cables? Or do I just put two power supplies and leave the +5 and ground pins connected as well? (This is never clearly explained at all)

I really am worried and a bit upset that, even though I spent more for everything to be the 'official' product, things don't turn out as smooth as they should be.

Thanks for any feedback, best regards,
Rafa.

gsh
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 1317
Joined: Sat Sep 10, 2011 11:43 am

Re: Rpi3 B + Official Touchscreen + Official Power Supply (revisited)

Wed Apr 04, 2018 9:23 am

Either way is fine, the polyfuse shouldn't be a problem, it's rated at 2.5A which should be the maximum supply anyway! It's safe either way, and is also safe for you to have two separate power supplies for both boards (there is a protection device to handle the case of two slightly different power supplies).

For Pi 2 we recommended powering from the display because the power supply wires were purposely spec'd to transfer power to the Pi. But with the increased power consumption of the Pi 3B and Pi 3B+ we would recommend powering from the Pi3.

If you are expecting to be using the full power supply of the 3B+ (including for example decoding 1080P30 HEVC) or supplying an amp out of the USB (i.e. plugging in a USB hard drive for example) then you should power the display from a second USB power supply to avoid issues.

Gordon
--
Gordon Hollingworth PhD
Raspberry Pi - Director of Software Engineering

RafaPolit
Posts: 4
Joined: Wed Apr 04, 2018 4:35 am

Re: Rpi3 B + Official Touchscreen + Official Power Supply (revisited)

Wed Apr 04, 2018 2:45 pm

A most helpful answer, thank you!

I do have an external audio card (DAC) hooked to the USB, as well as a dual fan. Just to be sure: if I go with the 2 PSU route, I should disconnect the jumper cables, right?

Also, maybe this small 'extended' instructions could make their way into the instructions? It would help a lot into not having to repeat this all over the forums :) .

Thanks again, much appreciated.
Rafa.

gsh
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 1317
Joined: Sat Sep 10, 2011 11:43 am

Re: Rpi3 B + Official Touchscreen + Official Power Supply (revisited)

Wed Apr 04, 2018 3:05 pm

Yes you can remove the jumpers
--
Gordon Hollingworth PhD
Raspberry Pi - Director of Software Engineering

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