bmatic
Posts: 6
Joined: Fri Dec 28, 2018 9:43 am

Raspberry Pi 4 PSU

Tue Jul 23, 2019 6:42 am

Hi all, I searched forum, but can not find exact problem as I have, so if there is answer to my question, but I did not see it, excuse me.
Until now I had Raspberry Pi 3B/B+ and I have powered it using 5V/5A PSU, like:

https://www.ebay.com/itm/263097995950

with DIY soldered micro USB connector, and it worked very vell.

So, now I ordered new Raspberry Pi 4, and DIY USB C connectors:

https://www.ebay.com/itm/123733979992

https://i.imgur.com/2VKQyvl.jpg

So the question is: is it enough for me to just simply solder +5V and ground wires to V and G pods/terminals on USB C connector, and will that power supply for Raspberry Pi work ? I also noticed there is SMD resistor between VBUS and CC pins, I did not measure it yet, what value should that ressistor measure to tell Raspberry Pi that my power supply is capable of delivering more than 3A current ?

Thank You.

andrum99
Posts: 855
Joined: Fri Jul 20, 2012 2:41 pm

Re: Raspberry Pi 4 PSU

Tue Jul 23, 2019 7:32 am

You are always best using an official Raspberry Pi power supply, at least to start with. That will allow you to rule out the power supply as the cause of any problem which you may have. Note that the rating of the power supply is somewhat irrelevant, since this is no guarantee that the power supply can actually supply what it says.

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RaTTuS
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Location: North West UK

Re: Raspberry Pi 4 PSU

Tue Jul 23, 2019 7:40 am

^WHS
but yes just solder up the +ve and -ve
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bmatic
Posts: 6
Joined: Fri Dec 28, 2018 9:43 am

Re: Raspberry Pi 4 PSU

Tue Jul 23, 2019 8:33 am

RaTTuS wrote:
Tue Jul 23, 2019 7:40 am
^WHS
but yes just solder up the +ve and -ve
Thank You for the information.

willieaames
Posts: 18
Joined: Tue Aug 09, 2016 6:14 am

Re: Raspberry Pi 4 PSU

Tue Jul 23, 2019 9:21 am

Thanks, This is helpful.

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PeterO
Posts: 5085
Joined: Sun Jul 22, 2012 4:14 pm

Re: Raspberry Pi 4 PSU

Tue Jul 23, 2019 10:14 am

andrum99 wrote:
Tue Jul 23, 2019 7:32 am
Note that the rating of the power supply is somewhat irrelevant, since this is no guarantee that the power supply can actually supply what it says.
While that is true for some of the "phone charger" type power supplies, the types of power supply linked to by bmatic are intended for use inside equipment and will be capable of supplying their rated max current without their output voltage drooping significantly.

Of course you can always be unlucky and get a "cheap knock off" one that doesn't work properly.

PeterO
Discoverer of the PI2 XENON DEATH FLASH!
Interests: C,Python,PIC,Electronics,Ham Radio (G0DZB),1960s British Computers.
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drgeoff
Posts: 9901
Joined: Wed Jan 25, 2012 6:39 pm

Re: Raspberry Pi 4 PSU

Tue Jul 23, 2019 11:56 am

bmatic wrote:
Tue Jul 23, 2019 6:42 am
I also noticed there is SMD resistor between VBUS and CC pins, I did not measure it yet, what value should that ressistor measure to tell Raspberry Pi that my power supply is capable of delivering more than 3A current ?
The RPi4B does not sense what the PSU is capable of delivering. It has no means of sensing that.

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american-pi
Posts: 14
Joined: Thu Jul 18, 2019 7:43 pm

Re: Raspberry Pi 4 PSU

Tue Jul 23, 2019 5:47 pm

i just bought this at home depot. $5.88
https://www.homedepot.com/p/CyberPower- ... /309469186
white-cyberpower-surge-protectors-gc306uhd-64_1000.jpg
white-cyberpower-surge-protectors-gc306uhd-64_1000.jpg (34.42 KiB) Viewed 644 times
this runs my Pi4B great.
you can buy USB C cables at the dollar tree all day.
Benchmarked, at 100% utilization and never once gets a low power icon.
100% stable! very reasonably priced.

trejan
Posts: 757
Joined: Tue Jul 02, 2019 2:28 pm

Re: Raspberry Pi 4 PSU

Tue Jul 23, 2019 6:16 pm

drgeoff wrote:
Tue Jul 23, 2019 11:56 am
The RPi4B does not sense what the PSU is capable of delivering. It has no means of sensing that.
The RPi 4 can detect what value the USB-C CC termination resistor Rp is which indicates the maximum current available. It doesn't appear to do anything with it though.

trejan
Posts: 757
Joined: Tue Jul 02, 2019 2:28 pm

Re: Raspberry Pi 4 PSU

Tue Jul 23, 2019 6:20 pm

bmatic wrote:
Tue Jul 23, 2019 6:42 am
I also noticed there is SMD resistor between VBUS and CC pins, I did not measure it yet, what value should that ressistor measure to tell Raspberry Pi that my power supply is capable of delivering more than 3A current ?
There is no resistor value for 5A and the RPi 4 only wants a maximum 3A anyway. Without USB PD, you get the choice of default USB power, 1.5A or 3A. The RPi 4 can detect the resistor value but doesn't appear to do anything with it.

You can feed 5V in via the USB-C socket or via the expansion header. Both will work fine. The PoE HAT powers the RPi via the expansion header.

pws
Posts: 92
Joined: Mon Apr 11, 2016 4:16 pm

Re: Raspberry Pi 4 PSU

Tue Jul 23, 2019 7:35 pm

trejan wrote:
Tue Jul 23, 2019 6:16 pm
drgeoff wrote:
Tue Jul 23, 2019 11:56 am
The RPi4B does not sense what the PSU is capable of delivering. It has no means of sensing that.
The RPi 4 can detect what value the USB-C CC termination resistor Rp is which indicates the maximum current available. It doesn't appear to do anything with it though.
Please provide the location of where this is documented. I would love to read the details....

trejan
Posts: 757
Joined: Tue Jul 02, 2019 2:28 pm

Re: Raspberry Pi 4 PSU

Tue Jul 23, 2019 10:20 pm

pws wrote:
Tue Jul 23, 2019 7:35 pm
Please provide the location of where this is documented. I would love to read the details....
No official documentation for it (yet). If you look at the schematics, you'll see the CC line is connected to one of the PMIC analog input pins. You can read the voltage on that pin using "vcgencmd measure_volts usb_pd"

PD_SENSE voltage = VBUS x 5100 / (Rp + 5100)

If PD_SENSE = 0V then nothing is connected to the CC lines or the RPi is being powered by the expansion header e.g. PoE HAT.

Rp = (5100 * VBUS) / (PD_SENSE - 5100)

56K ± 20% = Default USB current
22K ± 5% = 1.5A
10K ± 5% = 3A

It probably doesn't do anything with this value because of USB-A to USB-C cables that come with a 56K resistor and the ability to power the RPi via the expansion header.

This is with a RPi 4 powered by a USB-A to USB-C cable:

Code: Select all

$ sudo vcgencmd measure_volts usb_pd
volt=0.4100V

$ echo 5 * 5100 / 0.400 - 5100 | bc
58650

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