Can't connect my Soldering iron to my FairPhone 4

Question

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Jeremy Dahan @jeremydahan

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crwdns2931729:0crwdne2931729:0: yesterdayNhl 6, 2025

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Can't connect my Soldering iron to my FairPhone 4

Hi,

I can't get my FairPhone 4 to connect to the soldering iron.

I tried both the app and the web console (in Chrome for Android).

I am using the stock USB C cable.

I can connect to it on my macbook pro, and I updated the firmware to the latest version (1.4.1).

I also tried to enable USB debugging in the developer options and rebooting.

I tried inserting the USB C cable in a different orientation, and changing the cable (although it works fine on my macbook). Also tried with the power button in both positions when inserting the cable.

In all these scenarios, the error is "Connection Error Make sure you do not already have another connection open and try again". In Chrome, I simply don't see the device : "No compatible devices found".

What could be causing this ? How can I debug this issue ?

Best,

Jeremy

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I've forward your issue to the iFixit product folks, hang tight!

crwdns2934271:0yesterdayNhl 6, 2025crwdnd2934271:0 Dan crwdne2934271:0

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Jeremy Dahan @jeremydahan

crwdns2934065:0crwdne2934065:0: 37

2

crwdns2931729:0crwdne2931729:0: yesterdayNhl 6, 2025

crwdns2933897:0crwdne2933897:0

Well Gemini managed to pinpoint the issue!

When connecting my phone to the soldering iron via a USB-C hub, and connecting the iron using USB-A then it works fine in both Chrome and the iFixit App!

It only works with USB-A! I tried the same hub with the stock USB-C cable and another USB-C cable, with and without external power going into the hub. Nothing worked except when swapping the stock cable for a USB-A to USB-C cable.

So strange!

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Ah! So the issue is the handshake between the protocols USB 2.0 Vs USB 3.x. The hub assumes 3.0 when passing the data Vs 2.x the USB-A cable enforces.

I bet you going directly won't encounter the issue.

crwdns2934271:0yesterdayNhl 6, 2025crwdnd2934271:0 Dan crwdne2934271:0

I might not have been clear : I still cannot connect my soldering iron directly to my phone. I need to go through the hub and the USB A for it to be discovered. The USB A - USB C cable I used is rated for USB 3.0 (it is an external USB SSD cable). I agree : the problem probably lies in the handshake. Maybe the USB PD handshake fails here and the serial interface is confused ?

crwdns2934271:0yesterdayNhl 7, 2025crwdnd2934271:0 Jeremy Dahan crwdne2934271:0

I do remember encountering the exact same issue with another phone, but I did not try to enable USB debugging on that phone

crwdns2934271:0yesterdayNhl 7, 2025crwdnd2934271:0 Jeremy Dahan crwdne2934271:0

@jeremydahan - The USB Standards Group has made a mess! The connection is a group of Standards and the discrete names of each are often intermixed!

The first is the Letter which only defines the connectors and the pin assignments (A, B & C being the major ones)

Then we have the Protocol which is a giant mess! Here we have a hierarchy 3.x is supposed to support 2.x based connections. As the group fudged the naming up royally it's not clean!

Then we have the power PD stuff and then we have Apple adding Thunderbolt services into the mix!

So with the idea of a simple standard we have a kludge!

But wait! The cable & hardware folks needed fatter gage wires for power so to meet the spec some lines had to go! Which is where we have two distinct cables one for power with fewer data lines and other a full cable which can offer limited power and all of the data lines.

crwdns2934271:0yesterdayNhl 7, 2025crwdnd2934271:0 Dan crwdne2934271:0

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I've forward your issue to the iFixit product folks, hang tight! — Dan
Ah! So the issue is the handshake between the protocols USB 2.0 Vs USB 3.x. The hub assumes 3.0 when passing the data Vs 2.x the USB-A cable enforces.

I bet you going directly won't encounter the issue. — Dan
I might not have been clear : I still cannot connect my soldering iron directly to my phone. I need to go through the hub and the USB A for it to be discovered. The USB A - USB C cable I used is rated for USB 3.0 (it is an external USB SSD cable). I agree : the problem probably lies in the handshake. Maybe the USB PD handshake fails here and the serial interface is confused ? — Jeremy Dahan
I do remember encountering the exact same issue with another phone, but I did not try to enable USB debugging on that phone — Jeremy Dahan
@jeremydahan - The USB Standards Group has made a mess! The connection is a group of Standards and the discrete names of each are often intermixed!

The first is the Letter which only defines the connectors and the pin assignments (A, B & C being the major ones)

Then we have the Protocol which is a giant mess! Here we have a hierarchy 3.x is supposed to support 2.x based connections. As the group fudged the naming up royally it's not clean!

Then we have the power PD stuff and then we have Apple adding Thunderbolt services into the mix!

So with the idea of a simple standard we have a kludge!

But wait! The cable & hardware folks needed fatter gage wires for power so to meet the spec some lines had to go! Which is where we have two distinct cables one for power with fewer data lines and other a full cable which can offer limited power and all of the data lines. — Dan

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Can't connect my Soldering iron to my FairPhone 4

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