4 ms·

There needs to be a way to decide which device is the master, like the prompt on Android devices asking if you wish to power or be powered.

spookthesunset 9y ago
Wonder if you could do it on the cable with little embedded LED lights. One end turns red for "charging" the other turns blue for "supplying power". Would add to the BOM cost on the cable for sure, but it would not only be cool looking but rather useful.
- woodrowbarlow 9y ago
  oh yeah, because my bedroom doesn't have enough glowing devices when i'm trying to go to sleep. let's add LEDs to every cable too!
  - spookthesunset 9y ago
    Hah. Good point. Yes, too many devices want to put big giant blue LED's on their product.... even ones that are specifically targeted for the bedroom and specifically designed for sleeping...
- gargravarr 9y ago
  Barring the comments about adding more sources of light in a dark room (yep, I agree with this), I still appreciate the MagSafe adapter for my MBP lighting a tiny LED to say charging/full. The new USB-C MBPs we have at work don't have any indication whatsoever that the adapter is working unless the machine is booted and logged in (to pre-empt comments about the chime, what if it's muted, as is often true of workplace laptops?). MagSafe tells me no matter what state the computer is in. The LEDs don't have to be bright, just dim little indicators that are only really noticeable if you're looking for them. Then you get an instant idea of what the devices are doing.
giobox 9y ago
This. I’m always completely bemused when I first connect a USB-C charger to a USB-C battery pack before plugging into the wall - the LED on the charger lights up like the battery is powering the charger. There’s also tons of times where the device you want to power from the battery starts charging the battery instead. With both ends of the connector being identical I’m not sure there even is a _good_ way to fix this that ordinary consumers will understand, the better solution might have been to still keep different cable ends. I hope this mess eventually gets better.
- iratewizard 9y ago
  What's more annoying is when you connect a wacom tablet to your laptop and your laptop says it's charging. Only when your laptop is dead do you realize it was low battery. I had this happen during a demo and it was terrible.
parliament32 9y ago
The simplest solutions are directional cables (remember directional HDMI cables?) or plug-in order (supplier first, receiver last).
- joombaga 9y ago
  Not an EE, possibly a dumb question, but... do USB-C devices know that a cable has been plugged into them before the other end of the cable is plugged in to something else?
  - wolf550e 9y ago
    The plug can have (has?) resistors that let the socket "feel" it, even if the cable is not attached to anything.
  - cbluth 9y ago
    Just imagine this: Device A <--> Device B Device A receives the cable first, upon receiving the cable, Device A notices that the cable is not "hot" ("hot" in the sense that there is voltage/activity on the wire), so then Device A decides to "turn on" the cable, make it "hot". Now Device B receives the cable, it notices that the cable is already "hot" and decides that it must be the second device. I would imagine it could work that way, Im also pretty sure that the usb cables are "dumb" cables and not active cables like QSFP (these have chips at each end).
    - lopmotr 9y ago
      That assumes a device can tell the difference between not hot and not there, which was the parent's question.
    - arghwhat 9y ago
      This is not how USB Type C works. The cables are active (chipped), and the end devices have sense resistors. Each device can detect the presence and type of the cable, as well as the presence and type of an end device and total cable orientation (swapped or not). This is all done before power is applied, as USB Type C is very explicit about not going hot (apart from a weak 5V V_conn for powering the cable). Also, QSFP is not a cable, but a pluggable spec. A QSFP module is active, but the fiber optic cable you connect to it to is dumb. Link detection there works by sensing beam power.

spookthesunset 9y ago

Wonder if you could do it on the cable with little embedded LED lights. One end turns red for "charging" the other turns blue for "supplying power". Would add to the BOM cost on the cable for sure, but it would not only be cool looking but rather useful.

woodrowbarlow 9y ago
oh yeah, because my bedroom doesn't have enough glowing devices when i'm trying to go to sleep. let's add LEDs to every cable too!
- spookthesunset 9y ago
  Hah. Good point. Yes, too many devices want to put big giant blue LED's on their product.... even ones that are specifically targeted for the bedroom and specifically designed for sleeping...
gargravarr 9y ago
Barring the comments about adding more sources of light in a dark room (yep, I agree with this), I still appreciate the MagSafe adapter for my MBP lighting a tiny LED to say charging/full. The new USB-C MBPs we have at work don't have any indication whatsoever that the adapter is working unless the machine is booted and logged in (to pre-empt comments about the chime, what if it's muted, as is often true of workplace laptops?). MagSafe tells me no matter what state the computer is in. The LEDs don't have to be bright, just dim little indicators that are only really noticeable if you're looking for them. Then you get an instant idea of what the devices are doing.

giobox 9y ago

This. I’m always completely bemused when I first connect a USB-C charger to a USB-C battery pack before plugging into the wall - the LED on the charger lights up like the battery is powering the charger. There’s also tons of times where the device you want to power from the battery starts charging the battery instead. With both ends of the connector being identical I’m not sure there even is a _good_ way to fix this that ordinary consumers will understand, the better solution might have been to still keep different cable ends. I hope this mess eventually gets better.

iratewizard 9y ago
What's more annoying is when you connect a wacom tablet to your laptop and your laptop says it's charging. Only when your laptop is dead do you realize it was low battery. I had this happen during a demo and it was terrible.

parliament32 9y ago

The simplest solutions are directional cables (remember directional HDMI cables?) or plug-in order (supplier first, receiver last).

joombaga 9y ago
Not an EE, possibly a dumb question, but... do USB-C devices know that a cable has been plugged into them before the other end of the cable is plugged in to something else?
- wolf550e 9y ago
  The plug can have (has?) resistors that let the socket "feel" it, even if the cable is not attached to anything.
- cbluth 9y ago
  Just imagine this: Device A <--> Device B Device A receives the cable first, upon receiving the cable, Device A notices that the cable is not "hot" ("hot" in the sense that there is voltage/activity on the wire), so then Device A decides to "turn on" the cable, make it "hot". Now Device B receives the cable, it notices that the cable is already "hot" and decides that it must be the second device. I would imagine it could work that way, Im also pretty sure that the usb cables are "dumb" cables and not active cables like QSFP (these have chips at each end).
  - lopmotr 9y ago
    That assumes a device can tell the difference between not hot and not there, which was the parent's question.
  - arghwhat 9y ago
    This is not how USB Type C works. The cables are active (chipped), and the end devices have sense resistors. Each device can detect the presence and type of the cable, as well as the presence and type of an end device and total cable orientation (swapped or not). This is all done before power is applied, as USB Type C is very explicit about not going hot (apart from a weak 5V V_conn for powering the cable). Also, QSFP is not a cable, but a pluggable spec. A QSFP module is active, but the fiber optic cable you connect to it to is dumb. Link detection there works by sensing beam power.