RedHatter271
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Fixing the Pi 4 usb C issue by hand

Mon Aug 26, 2019 9:24 pm

I've been reading up on the cause of the raspberry 4's usb C issue (this article is a really good write up) and it seems to me that it would be relatively easy to fix by hand. All that would need to be done is too break the connection between CC1 and CC2 then connect a 5.1K resistor between CC1 and ground.

Has anyone attempted this? Would it work?

raspipat
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Re: Fixing the Pi 4 usb C issue by hand

Tue Aug 27, 2019 1:27 am

I think I remember reading somewhere that the circuit board trace that would need to be cut runs beneath the USB-C connector. Thus, the connector itself would need to be unsoldered from the board in order to effectively make the change.
I'll try to see if I can dig up the source.

EDIT: It was in the comment stream in the article here

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rpdom
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Re: Fixing the Pi 4 usb C issue by hand

Tue Aug 27, 2019 7:42 am

spooker wrote:
Tue Aug 27, 2019 7:23 am
Do we have any idea when rpi4 revision 2 that will fix this major flaw will be available?
will be
No. The RPF do not announce release dates in advance. We do not know when the fix for this minor inconvenience will be incorporated into a revised version. It may be that they are waiting to see if any other fixes need to happen first.
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pootle
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Re: Fixing the Pi 4 usb C issue by hand

Tue Aug 27, 2019 7:44 am

Could it be fixed by making (by hand) a short extension cable incorporating the resistor?

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rpdom
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Re: Fixing the Pi 4 usb C issue by hand

Tue Aug 27, 2019 8:01 am

pootle wrote:
Tue Aug 27, 2019 7:44 am
Could it be fixed by making (by hand) a short extension cable incorporating the resistor?
I think that is very likely. It is purely a passive circuit.
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hippy
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Re: Fixing the Pi 4 usb C issue by hand

Tue Aug 27, 2019 12:04 pm

pootle wrote:
Tue Aug 27, 2019 7:44 am
Could it be fixed by making (by hand) a short extension cable incorporating the resistor?
Possibly. That would leave the Pi's PD_SENSE line monitoring only CC1 or CC2 so you would have to determine which it should be and check whether the firmware still handles things correctly.

drgeoff
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Re: Fixing the Pi 4 usb C issue by hand

Tue Aug 27, 2019 1:19 pm

hippy wrote:
Tue Aug 27, 2019 12:04 pm
pootle wrote:
Tue Aug 27, 2019 7:44 am
Could it be fixed by making (by hand) a short extension cable incorporating the resistor?
Possibly. That would leave the Pi's PD_SENSE line monitoring only CC1 or CC2 so you would have to determine which it should be and check whether the firmware still handles things correctly.
If the intent is merely to work with smart PSUs (eg Apple) and cables I would wire the two resistors to the appropriate pins of the USB-C socket end of the adaptor cable. And don't wire anything except the power pns of that socket to the power pins of the plug on the adaptor cable. AIUI the RPi does not really care about the other pins of its USB-C socket if only being used for 5 volt power input.

hippy
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Re: Fixing the Pi 4 usb C issue by hand

Tue Aug 27, 2019 1:56 pm

drgeoff wrote:
Tue Aug 27, 2019 1:19 pm
AIUI the RPi does not really care about the other pins of its USB-C socket if only being used for 5 volt power input.
The Pi 4B does take CC1 and CC2 to PD_SENSE which is read by an ADC channel on the PMIC. What the firmware does with that information I have no idea.

It might be best not to connect either CC1 or CC2 to the USB-C on the PI because I recall using either of the CC's as VCON can potentially deliver 5V, more than I believe the PMIC ADC is rated to handle, 3V
Last edited by hippy on Tue Aug 27, 2019 2:05 pm, edited 1 time in total.

drgeoff
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Re: Fixing the Pi 4 usb C issue by hand

Tue Aug 27, 2019 2:03 pm

hippy wrote:
Tue Aug 27, 2019 1:56 pm
drgeoff wrote:
Tue Aug 27, 2019 1:19 pm
AIUI the RPi does not really care about the other pins of its USB-C socket if only being used for 5 volt power input.
The Pi 4B does take CC1 and CC2 to PD_SENSE which is read by an ADC channel on the PMIC. What the firmware does with that information I have no idea.
I worded my sentence carefully. We are not in disagreement. :)

raspipat
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Re: Fixing the Pi 4 usb C issue by hand

Tue Aug 27, 2019 5:04 pm

After my initial response to the opening post of this thread, I got to thinking... rather than desoldering the entire USB-C connector, why not just lift one of the CC pins from it's PCB pad.

WARNING!!! I'm not advocating anyone actually try what I'm about to describe. This is not for the faint-of-heart.
One wrong move and your RPi could be a paper weight. But, as a data point, in support of the theorists out there.... this is my experience with just one alternative modification.

Using a common household stick pin, under magnification, I decided to try lifting the CC1 pin (that's the pin designated as "A5" on the physical connector [*1]) from it's PCB pad and then solder a 5.1kohm resistor between that pin and ground. See the attached closeup image.

As expected - I am now able to power my RPi4 using the emarked cable from my MacBook Pro and a Google Pixel phone charger (something that couldn't be done prior to this modification).

Reference:
[*1] - For details of the RPi4's USB-C connector, see the CSP-USC16-TR Valcon USB Type C Surface Mount PCB Socket data sheet
Attachments
RPi4B-USBC-MOD-sm.jpg
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drgeoff
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Re: Fixing the Pi 4 usb C issue by hand

Tue Aug 27, 2019 6:34 pm

Give that man a round of applause.

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Re: Fixing the Pi 4 usb C issue by hand

Tue Aug 27, 2019 7:18 pm

spooker wrote:
Tue Aug 27, 2019 7:23 am
Do we have any idea when rpi4 revision 2 that will fix this major flaw will be available?
The flaw is minor, so there's no hurry. I doubt the change will result is a Rev. 2 of the PCB. More likely to be 1.1 or 1.2, or even 1.0.1. I do not, personally, expect to see a revised board for about 6 months. Could be sooner, could be longer. It all depends on whether or not any other board corrections are found that need to be done and how urgent they are.

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Re: Fixing the Pi 4 usb C issue by hand

Tue Aug 27, 2019 7:25 pm

drgeoff wrote:
Tue Aug 27, 2019 6:34 pm
Give that man a round of applause.
Bonus points for the old-school rod-and-cap through-hole resistor as well.
Rockets are loud.
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bootdsc
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Re: Fixing the Pi 4 usb C issue by hand

Tue Sep 24, 2019 6:34 pm

raspipat wrote:
Tue Aug 27, 2019 5:04 pm

As expected - I am now able to power my RPi4 using the emarked cable from my MacBook Pro and a Google Pixel phone charger (something that couldn't be done prior to this modification).
Just out of curiosity after making this modification have you tested the USB-C host functionality is still working?

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Re: Fixing the Pi 4 usb C issue by hand

Tue Sep 24, 2019 7:21 pm

jdb wrote:
Tue Aug 27, 2019 7:25 pm
drgeoff wrote:
Tue Aug 27, 2019 6:34 pm
Give that man a round of applause.
Bonus points for the old-school rod-and-cap through-hole resistor as well.
Strangely enough I was looking at the same picture and thinking, that makes sense as it would be a pita to do with one of those newfangled SMT resistor packages, though I have tacked leads onto the ends of them to when cutting and strapping.

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Re: Fixing the Pi 4 usb C issue by hand

Wed Sep 25, 2019 2:25 am

jcyr wrote:
Tue Sep 24, 2019 7:52 pm
If board space is not an issue, through hole components are always easier to work with manually. BTW, SMT components have been around for a few decades now... hardly newfangled!

Brilliant USB-C fix though.
Its all about perspective. I got involved with electronics prior to their existence. First commercial foray pre university was building and selling computers that we were building (as is soldering up from bare pcbs). Made lots of money building 80 column cards and memory expansion boards for Apple computers. Some of the boards we were buying were single sided, and needed to be drilled prior to stuffing. All the early PCs were through hole. I think I still have some XT and AT motherboards lurking in the basement.

Moved on to the DMS100 assembly plan at NorTel and again all through hole, was well into my career in telecom before SMT was a thing. At Mitel we still had mylars of board layers. Was a different world from multi GHz clocks and all balanced and balanced impedance. Certainly have done time with a rework stations but now I am back to through hole when we build little whoseamawhats on the robotics team I mentor as it is way easier to teach high school kids how to breadboard and solder with through hole components.

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Imperf3kt
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Re: Fixing the Pi 4 usb C issue by hand

Wed Sep 25, 2019 10:20 pm

bjtheone wrote:
Wed Sep 25, 2019 2:25 am
Its all about perspective. I got involved with electronics prior to their existence.
Im sure you could have phrased that better. There is evidence of "electronics" dating back to at least ancient Egypt.
https://www.express.co.uk/news/weird/10 ... attery-spt

I doubt you are over 4000 years old.
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Re: Fixing the Pi 4 usb C issue by hand

Wed Sep 25, 2019 10:50 pm

Imperf3kt wrote:
Wed Sep 25, 2019 10:20 pm
bjtheone wrote:
Wed Sep 25, 2019 2:25 am
Its all about perspective. I got involved with electronics prior to their existence.
Im sure you could have phrased that better. There is evidence of "electronics" dating back to at least ancient Egypt.
https://www.express.co.uk/news/weird/10 ... attery-spt

I doubt you are over 4000 years old.
Oh dear. You are confusing "electricity" and "electronics". They are not the same thing.
And the article you cite ends with:
However, studies suggest that the artefact dates back to the early Medieval period.

If true, it is centuries younger than the pyramids.
So even the tabloid newspaper report thinks the claim of Ancient Egyptian electrical power is suspect.

It is also clear (though open to ambiguity) that bjtheone's phrase "their existence" refers to SMT components.
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bjtheone
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Re: Fixing the Pi 4 usb C issue by hand

Thu Sep 26, 2019 1:54 pm

Imperf3kt wrote:
Wed Sep 25, 2019 10:20 pm
bjtheone wrote:
Wed Sep 25, 2019 2:25 am
Its all about perspective. I got involved with electronics prior to their existence.
Im sure you could have phrased that better. There is evidence of "electronics" dating back to at least ancient Egypt.
https://www.express.co.uk/news/weird/10 ... attery-spt

I doubt you are over 4000 years old.
I could have phrased it better but the "their" is referring to SMT, and if I was truly being pedantic I should have said "I got involved with electronics prior to the wide spread adoption of SMT in telecom, or consumer grade computers". SMT was being mucked about in r&d labs as early as the late 60s and early 70s, started appearing commercially in the 80s and pretty much took over by the late 90s. I remember the first SMT line card.

kiltannen
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Re: Fixing the Pi 4 usb C issue by hand

Mon Oct 07, 2019 3:35 am

raspipat wrote:
Tue Aug 27, 2019 5:04 pm
After my initial response to the opening post of this thread, I got to thinking... rather than desoldering the entire USB-C connector, why not just lift one of the CC pins from it's PCB pad.
GENIUS!

This now gives me confidence to buy myself a Pi 4

Thanks for doing the Beta Testing on this fix for us all :D

scaramonga
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Re: Fixing the Pi 4 usb C issue by hand

Mon Oct 07, 2019 1:54 pm

Neat job :)

I'd attempt myself, but I don't trust my eyes now, lol ;)

jamesh
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Re: Fixing the Pi 4 usb C issue by hand

Mon Oct 07, 2019 2:21 pm

kiltannen wrote:
Mon Oct 07, 2019 3:35 am
raspipat wrote:
Tue Aug 27, 2019 5:04 pm
After my initial response to the opening post of this thread, I got to thinking... rather than desoldering the entire USB-C connector, why not just lift one of the CC pins from it's PCB pad.
GENIUS!

This now gives me confidence to buy myself a Pi 4

Thanks for doing the Beta Testing on this fix for us all :D
I'd just like to know why this has changed your confidence level in the Pi4, for my own nosiness. It was a fault only seen on expensive power supplies (more than the Pi4 cost in most cases!), and the huge majority of people simply purchased an official supply anyway. Whilst it will be fixed in a future revision of the board, as a problem it really was massively overblown by the clickbait attractors.
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supersjimmie
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Re: Fixing the Pi 4 usb C issue by hand

Thu Nov 14, 2019 9:30 am

Instead of having to modify the rPI4 board, would it be possible to add the 5.1k resistor inbetween a male/female usb-c connector?
That way we can have just a small converter-cable with the resistor instead of the risk of ruining the rpi4 board.

Power adapter USB-C -> diy USB-C [male] -> diy cable with resistor -> USB-C [female] -> RPi4

hippy
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Re: Fixing the Pi 4 usb C issue by hand

Thu Nov 14, 2019 11:00 am

supersjimmie wrote:
Thu Nov 14, 2019 9:30 am
would it be possible to add the 5.1k resistor inbetween a male/female usb-c connector?
I can't see any reason that wouldn't work. You would need to find a female-male USB-C cable to modify or create an adapter board with a USB-C female socket.

I have never seen the first and you would likely have to make the second yourself. I doubt any company would create an adaptor for commercial sale as it would probably be too costly given the small market for such a board and the fact the issue is going to get fixed at some point.

The best hope would be that an individual designs such a thing and orders more than they need which they are willing to sell.

One would have to prototype it to ensure it didn't introduce too many losses in the cable.

It is probably easier to just buy an official PSU given it's very reasonably priced.

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procount
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Re: Fixing the Pi 4 usb C issue by hand

Thu Nov 14, 2019 11:01 am

Or maybe just add 2 back to back adaptors:
Usb-c/micro-usb -> micro-usb/usb-c.?
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