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terekgabor
Senior Member

Joined: 02/01/2026
Location: Hungary
Posts: 102

Posted: 04:06pm 14 Jun 2026

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Hello!

I just had free time to solder a Pico 2 to HDMI-USB reference board.
Everything is working expect USB.

I can upload firmware, I can start is. I have HDMI output with logo screen and cursor.

I attached junpers, red USB hub LED is active.

But any USB keyboard I connect is not working. No green LED for the USB port where the keyboard is plugged in.

Where to start the debug?

Thanks!
G@bor

homa

Guru

Joined: 05/11/2021
Location: Germany
Posts: 627

Posted: 04:32pm 14 Jun 2026

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G@bor,
have you checked the solder joints from underneath? If in doubt, make sure you resolder them!!

https://www.thebackshed.com/forum/ViewTopic.php?TID=17301&P=7#231405

Matthias
Edited 2026-06-15 02:35 by homa

matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 11500

Posted: 05:14pm 14 Jun 2026

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Also, there was a bad batch of the hub chips shipped. If Matthias suggestion doesn't work then referring to the post he references remove R54 and R55. These are a potential divider that signals to the hub chip that there is a current overload. The bad chips see a valid current as overload. With the resistors removed it works.
Can you program the firmware using the prog usb connector? If you can the USB connections are OK and the resistors are the next thing to test. You are connecting the jumpers 1 to 2 and 3 to 4?

terekgabor
Senior Member

Joined: 02/01/2026
Location: Hungary
Posts: 102

Posted: 06:25pm 16 Jun 2026

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Hello,

I used the USB programming connector working good.
Jumpers are right.

I forgot to solder the 4th hola from backside, but this is only for better cooling if I read well.

Resistors are to small for me to remove, I have to look for somebody can do this to check.

Thanks.

G@bor

johnnyzero2

Newbie

Joined: 24/03/2026
Location: United States
Posts: 1

Posted: 07:31pm 16 Jun 2026

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I recently received a bunch of boards from PCBWay that had this same issue, likely caused by the funky hub chips that Peter mentioned.

I can confirm that simply removing R54 and R55 will do the trick. Not having any real SMD soldering skills or a hot air reflow station to do it the "right way", I was able to just carefully cut them off the board using the tip of a small pair of diagonal cutters. I wasn't concerned about possibly tearing the pads, since they're not going to be used anyway.

Hope this helps.
Edited 2026-06-17 05:35 by johnnyzero2

Volhout
Guru

Joined: 05/03/2018
Location: Netherlands
Posts: 5931

Posted: 05:36am 17 Jun 2026

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When you only have to remove the resistors, the simplest way is to use a normal soldering iron, plenty of solder, and heat the resistors. The resistors Will be invisible in the blob of solder, and can easily be move sideways, from the pads with little help of the tip of the soldering iron. Once free from the pads, let the solder blob cool, and get did of it( the resistors still embedded in the Solder).

Volhout

PicomiteVGA PETSCII ROBOTS

phil99

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Joined: 11/02/2018
Location: Australia
Posts: 3289

Posted: 07:14am 17 Jun 2026

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A bright light and/or magnifying glass help.
After removing them look for solder bridges between the pads. Then, if necessary, clean the pads with solder-wick and a hot iron.

Mixtel90

Guru

Joined: 05/10/2019
Location: United Kingdom
Posts: 8910

Posted: 07:15am 17 Jun 2026

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For maneuvering solder never underestimate the traditional tools of toothpicks and a sharp pencil, especially the latter. Liquid solder will flow away from a pencil lead under its own surface tension. Toothpicks are great for pushing SMD parts around or holding them in position. They have the advantage that they are a little more rugged than graphite but they do tend to get mashed under pressure. I use them for clearing solder bridges.

{Off Topic - For those with deep pockets (lol!) that want to experiment with SMD, a "400W" PTC heating plate with magnetic feet from AE (about £3), some wooden spring clothes pegs (to hold your PCB in position) and a steel baking sheet to protect the bench will provide a very usable SMD soldering hotplate. Some solder paste and gel flux and off you go. (I do recommend a 3-core mains lead and connect the Earth to a solder tag on the hotplate though. You can't play too safe with Chinese PTC heater insulation values!). Take care. The plate gets to about 250°C in about 30s and there is no indication of it. No thermostat needed.}

Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs

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