I lost a good two hours the other day on an insufficiently documented device, looking for a way to flash a new firmware onto it.
dmesg was absolutely silent about it when I plugged in or out my C-C USB cable although the device switched on when I was using a simple charger instead. I opened it up to see if there was a special switch or something to put it in firmware flashing mode, to no avail. The little documentation I had only mentioned using one of the USB port.
In the end, out of ideas, I switched cables (even though I knew my cable was perfectly fine). As soon as I plugged in a A-C USB cables, everything worked immediately...
While the device is ultimately to blame, many PD chargers will work anyway (by dangerously assuming 5V when there are no CC resistors). My Anker chargers do this.
I don't buy and return products that don't charge with a single usb-c cable. How can I expect good quality from a product if the maker saves on ¢1 cent? It's 2026 yet new products still keep people from going all usb-c.
As someone with a bunch of "USB-C" devices that do this, I'd wondered for years why nobody sold these. I recently just found them on Aliexpress in a more finished format (nice-looking case and such), so I'm hopeful they'll start to filter out into the world more. (If you're interested, do a search for "usb c resistor" and you'll find them for ~$2-$4.)
Oh, I made one of these not too long ago with those 4-pin solderable aliexpress USB-c pcbs. One side has the resisters, and I just joined them with headers. A few months ago I was looking for something just like this, but couldn’t find anything. I think a pack of 10 male and 10 female ports with CC resistors cost <$10, but I suppose this is a more elegant and accessible solution (plus, may actually pass more lines through).
Anyone in test for the domain able to attest that formal USB compliance verification would have been to detect this design defect?
I lost a good two hours the other day on an insufficiently documented device, looking for a way to flash a new firmware onto it.
dmesg was absolutely silent about it when I plugged in or out my C-C USB cable although the device switched on when I was using a simple charger instead. I opened it up to see if there was a special switch or something to put it in firmware flashing mode, to no avail. The little documentation I had only mentioned using one of the USB port.
In the end, out of ideas, I switched cables (even though I knew my cable was perfectly fine). As soon as I plugged in a A-C USB cables, everything worked immediately...
What was the device? Somebody experiencing the same problem might appreciate the tip.
I did not know this was a thing.
I have a couple of devices that do not charge on a usb c source. I have to use a USB A - C cable on their shitty usb-c ports.
Now that I know the probable reason I’m more annoyed.
While the device is ultimately to blame, many PD chargers will work anyway (by dangerously assuming 5V when there are no CC resistors). My Anker chargers do this.
Interesting. I thought 5V is a safe default for USB when in doubt and risk of damage is nil even if it's assumed.
There's nothing dangerous about it.
No Type-C receptacle featuring device can assume there will be no Vbus voltage on attachment from the other side, regardless of CC signals.
are there devices that are damaged by 5V?
There were some higher profile products that left this out like the original revisions of the raspberry pi 4.
I don't buy and return products that don't charge with a single usb-c cable. How can I expect good quality from a product if the maker saves on ¢1 cent? It's 2026 yet new products still keep people from going all usb-c.
As someone with a bunch of "USB-C" devices that do this, I'd wondered for years why nobody sold these. I recently just found them on Aliexpress in a more finished format (nice-looking case and such), so I'm hopeful they'll start to filter out into the world more. (If you're interested, do a search for "usb c resistor" and you'll find them for ~$2-$4.)
Are you sure they aren't C-to-C data blockers?
Oh, I made one of these not too long ago with those 4-pin solderable aliexpress USB-c pcbs. One side has the resisters, and I just joined them with headers. A few months ago I was looking for something just like this, but couldn’t find anything. I think a pack of 10 male and 10 female ports with CC resistors cost <$10, but I suppose this is a more elegant and accessible solution (plus, may actually pass more lines through).
Hagibis makes one that isn't a bare PCB. B0GLFGTLW9 on Amazon.com, for me today it's showing $6.99 for a 2-pack.