USB Type-C -vs- USB 3.0/3.1 -vs- USB 2.0 || Concerning Nexus 5X & 6P

[Elnrik]

Hi all.

There has been a lot of confusion on the Type-C port on the Nexus devices, all of the different USB specs, how it all relates to charging using USB Type-C devices, and what kind of data speeds you can get from Type-C devices. I did a fair bit of fact finding, and thought I'd consolidate everything I learned into one topic. For now, this is kind of a "living document" in that I am constantly updating the OP to consolidate knowledge. I'm not going to post everything you could ever know about USB specs here, but have provided the links! I am going to try to keep it focused on items as they relate to the new Nexus phones. As always, if you find this helpful, I'd appreciate the thanks.

I feel the state of USB-C cables and charging devices has been fleshed out well enough, and as such, I'm no longer updating this thread.

News:
Good news for consumers! Amazon bans non-compliant USB Type-C cables.

Resources:
https://plus.google.com/+BensonLeung
Reviewed cables: https://plus.google.com/collection/s0Inv
USB Type C Explained: https://plus.google.com/collection/0Vdov
USB Type C News: https://plus.google.com/collection/EKnov

http://www.usb.org/developers/docs/ (Official specifications.)
http://arstechnica.com/gadgets/2015...clear-up-confusion-about-all-these-usb-specs/
http://www.cnet.com/news/usb-type-c-one-cable-to-connect-them-all/
https://en.wikipedia.org/wiki/USB_Type-C
ACTUAL TESTING: http://www.droid-life.com/2015/10/19/nexus-6p-nexus-5x-quick-charge/
https://play.google.com/store/apps/details?id=com.gombosdev.ampere&hl=en
http://forum.xda-developers.com/showpost.php?p=63614861&postcount=91

What rate will my Nexus charge at with other devices?
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When you connect your Nexus to a host, the devices must negotiate which charging rates can be used.

Type C hosts can negotiate with Type C devices using a specific wire in the cable known as the Configuration Channel - aka, the CC wire.

If you are using a Type-A adaptor or cable, the cable must identify itself as a Legacy USB connection (Type-C being converted to Type-A) using a pull-up resistor on the CC wire, grounded to the vBus wire. This is because the CC pin does not exist on Type-A ports. The Nexus will see the resistor, know it is on a legacy port, and it will then perform power negotiation using the USB BC2.1 protocol on the USB 2.0 wires in the cable. If the host is not BC2.1 capable, it will draw default USB current. (See page 149, table 4-12 for order of precedence.)
USB Type-C ports and chargers will provide 5V at 3A (15W) - true fast charging.
USB Type-A ports and chargers using USB BC2.1 should provide a max of 5V at 1.5A (7.5W).
Standard USB 3.0 can provide 5V @ 0.9A (4.5W)
USB 2.0 defaults to 5V @ 0.5A (2.5W).
What this means is that when your phone negotiates power with the host (your charger or computer), whatever current level they mutually agree upon is what your phone will attempt to draw. If you connect to a USB 2.0 port on your computer, a very old port which does not support the BC 2.1 protocol, then the most you'll be drawing is 0.5A. If you connect to a dedicated charging device which supports BC 2.1, it should draw up to 1.5A. Charging rates depend on this negotiation. Out of specification cables do not allow this negotiation to occur correctly. This may lead to faster charging, but you also risk exceeding the capabilities of your charger which may be dangerous.

As you can see, there is a big difference between 15 watts for Type-C fast charging and 2.5 watts for USB 2. Furthermore, please be aware that the phone will pull less current as the battery charges. A Nexus at 80% battery will pull less current than a Nexus at 20% battery.

In any regard, consider USB Type A to be the weak link in charging your Nexus.

Table 4-12:



What charger and cable will work with my new Nexus, and will it support fast charging?
___________________________________
My suggestion would be to make the move to Type-C car and wall chargers. You will eliminate the chance of using out of specification Type-A cables, and ensure you are always fast charging. Type-C will soon be the de facto interface for USB, so why not future proof yourself now.

If you have to use Type-A adaptors and cables, understand that there will be limitations and concerns to be aware of. Out of specification cables being the primary issue, which is explained below. Further, your charging rates will be half (or less) than what Type-C is capable of.

Table 2-1 shows all supported power specs for Type-C charging. Please understand that Type-A ports/cables will only support up to the BC 2.1 charging level of 1.5A. If it goes beyond this, your cable may not be compliant with USB specifications.

Hi. I'm an engineer at Google who has worked on USB Type-C on the Pixel and Nexus projects.
The reason that the Google chargers and cables are capable of 5V 3A support is because not only the cables but the port on the other end is certified for the higher 3A ceiling. You will notice that the cable that came with your Nexus 5X or 6P has USB Type C on both ends.
This ensures that not only the cable, but the connectors and the charging circuitry on the other side of the cable can support 3A before the phone starts to charge.
When you have a legacy cable like this one, the connector on the other side is a USB Type-A connector, which can be plugged into any USB port built since 1997, for example your ancient Pentium II PC may have a USB port that this cable could be plugged into.
NONE of those USB Type-A ports are rated to support 3A, so many of the USB Type-A to Type-C cables available on Amazon that claim they are rated at 3A and configure the identifier resistor to tell the phone to charge at 3A are not in compliance and could do damage to your charger, hub, or PC if you try to charge at 3A.
When you have a legacy cable like this, 2.4A, which is negotiated over a BC1.2 protocol like CDP or DCP, is appropriate over the Type-A connector. Any cable that you buy that claims 3A support I would be extremely wary of plugging into any of your hubs, PCs, or dedicated chargers.

By the way, the maximum current of 1.5A is defined by the BC1.2 specification for CDP and DCP, but in practice, a range of other current values are possible using Apple's proprietary protocol or other protocols that bump up the defacto maximum current with a Type A connector on one end up to 2.4A, as long as the charger and the device both support that current limit.
However, keep in mind that there are 3 different termination possibilities. If you have the USB Type-C Specification 1.1, take a look at section 4.11.1, and at Table 4-13.
You'll notice that DFP Advertisement lists "Default USB Power" "1.5A @ 5V" and "3.0A @ 5V". It's important to read note 1. If you are making a legacy USB cable that has Type-C plug on one end, and a Type A plug on the other or a Type-B receptacle, you must use the "Default USB Power" termination, and NOT the "1.5A" one. Default USB power defers to BC 1.2 spec for current negotiation, so that such a cable that is attached to a basic 500mA SDP port should only draw 500mA, for example. Make sure to use a 56 kΩ pullup!

As referenced in the quote, Table 4-13:




What about QuickCharge 2.0/3.0 chargers!? My Nexus has a Qualcomm chip, isn't it compatible?
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No. Google has stated that it is not implemented in the new Nexus devices.

QuickCharge works by increasing voltage and amperage to charge quickly. The USB Type-C standard only works this way in USB PD modes, otherwise voltage never varies from 5V. This means that QuickCharge 2.0/3.0 is completely different from USB Type-C charging methods.



But my 2.4A rated Type-A charger works, and my phone says it is Fast Charging. What's the deal?
___________________________________
Your Nexus may report as fast charging if the Type-A cable you use is not compliant with USB specs.

Threads on this forum have confirmed that the phone will pull 3A (or about 2990mA) from the stock charger. These results were verified using apps such as Ampere. When using 3rd party equipment (non-OEM cables and chargers), I would suggest using an application such as Ampere to ensure that you are not exceeding the maximum rating of the charger or cable. Doing so can be dangerous! It will also verify exactly how much current your phone is pulling to charge - information I've found helpful if for no other reason than to satisfy my own curiosity.

If you are unsure if your cable is compliant, you can test it using the methods found here: http://www.androidheadlines.com/201...usb-type-c-for-nexus-5x-6p-compatibility.html



So, how should you approach charging and connecting your Nexus to other devices?
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The same way you would any other device - plug it into the best thing you have available.
For connecting to computers, use the best port you have available. Type-C to Type-C > USB 3.x to Type-C > USB 2 to Type-C.
For chargers, try to match OEM specs: 5 volts at 3 amps output using a Type C connector.
If you have to use an adapter (Type-A to Type-C), Make sure you use compliant cables!




What data connection speeds will I get on my Nexus using Type-C?
___________________________________
If you want to dig deep into this, look at the "USB Type-C Specification Release 1.1.pdf" doc from USB.org, it defines on page 19 the types of plugs and cables for Type-C, including the USB 2.0 Type-C port. Starting at page 57 it defines all of the wires/pins for the different cables. Comparing table 3-10 to 3-11, you can see that all of the SDP (shielded differential pair) signal pins/wires are missing in the USB 2.0 Type-C connections. These are your high speed data connection wires. The Vbus, Vconn, cc, GND wires are all still present to support Type-C power delivery.

So, in other words, there are USB 2.0 Type-C ports, and USB 3.0 ports. For devices which don't require up to 100 watts of power, or won't use up to 10GB/s transfer speeds, the USB-C 2.0 port may commonly be used. The Nexus 5X & 6P fall into this category. What connection speeds are you going to get with the Nexus? USB 2.0 speeds.

Full Featured USB Type-C Cable:


USB 2.0 Type-C to Type-A cable:


If I left any glaring omissions from this, please follow up. I'd love to have all the info we can get.

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I wanted to put in this addition to the op. Thanks to @aaron_huber for putting this information up.
Aaron said:

A wire is a wire, but in this case the magic is in the charger, the device, AND THE CABLE. From the USB-C Wikipedia page:

Full-featured USB Type-C cables are active, electronically marked cables that contain a chip with an ID function based on the configuration data channel and vendor-defined messages (VDMs) from the USB Power Delivery 2.0 specification. USB Type-C devices also support power currents of 1.5 A and 3.0 A over the 5 V power bus in addition to baseline 900 mA; devices can either negotiate increased USB current through the configuration line, or they can support the full Power Delivery specification using both BMC-coded configuration line and legacy BFSK-coded VBUS line.

The 6P does not support the full PD spec per Google, but it does use the "configuration line" which is an extra wire in the USB-C cable hooked up to an extra pin in the phone/charger to talk to the charger and negotiate extra current. If you don't have a USB-C cable with the extra pins/wires plugged into a USB-C charger on the other end that also has the extra pins to do the negotiation, then the phone will fall back to a lower current because the spec requires it. If you plug it into a USB-A charger or use a USB-A to USB-C cable then all you get are four wires - the "configuration line" to do the negotiation doesn't exist.​

========================================

* Type-C capabilities exceeds previous USB Type-A 3.1 / 2.0 specifications:
** 2 way power transfer
** Universal plug type (reversible plug)
** Much high transfer speeds (10GB/s)
** Much higher charging capabilities (Up to [email protected] = 100W via USB PD)
** Alternate data modes for devices (Display port / Audio)

Known Type-C capabilities for Nexus 5x & 6P:
+ USB 2.0 Data transfer speeds
+ Full fast charging through USB Type-C ports or specifically designed 5v/3a capable Type-C chargers only
- Not Qualcomm QuickCharge compatible (may draw more current for charging than a standard USB port though, see below)
- No HDMI out (It is not type-c alternate mode capable.)
- Not USB-PD capable

Thanks all!

 

[ylexot]

Nice post!

Sent from my LG-V410 using Tapatalk

 

[Elnrik]

Nice post!
Sent from my LG-V410 using Tapatalk

Thank you!

 

[toyanucci]

Are 3.1 Type C cables backward compatible with 2.0 type C devices? I ask because if they are wouldn't it make sense for people to buy USB 3.1 Type C cables for future proofing vs 2.0?

I am in the market for a long cable and am confused as to which of the cables below to chose.

http://www.amazon.com/gp/product/B0...able&qid=1444414379&ref_=sr_1_59&s=pc&sr=1-59

http://www.amazon.com/Cable-Matters...ME5bDiL&dpSrc=sims&preST=_AC_UL160_SR160,160_

 

[Chilidog]

Are 3.1 Type C cables backward compatible with 2.0 type C devices? I ask because if they are wouldn't it make sense for people to buy USB 3.1 Type C cables for future proofing vs 2.0?

I am in the market for a long cable and am confused as to which of the cables below to chose.

http://www.amazon.com/gp/product/B0...able&qid=1444414379&ref_=sr_1_59&s=pc&sr=1-59

http://www.amazon.com/Cable-Matters...ME5bDiL&dpSrc=sims&preST=_AC_UL160_SR160,160_

USB type c is just the physical connector it has nothing to do with the usb 2.0 or 3.0 so you might as well by the fastest ones

What we do need to worry about is whether or not the cable itself supports charging at 3A 5v

 

[Elnrik]

Looking at the two, it appears that the Cable Matters product is a cable designed to connect a computer with Type-C port to a peripherals with USB 2.0 Type-C ports. (Like the Nexus 6p.) The maximum data speeds for this would be USB 2.0 speeds. Looks like a very nicely constructed cable - look at the connection ends, and polished metal. If all you were doing is connecting smart phones to your laptop, this is the type of product I would buy.

The J&D cable appears to be a full-feature type-c cable, and should support every supported type-c data rate. I'm not in love with the picture of the product though. Doesn't look quite as nice as the Cable Matters product. If you wanted to connect two devices with full 10GB/s connectivity, this would be the type of cable I would get.

It is my opinion that the two products are good examples of a well made USB 2.0 Type-C cable and a cheaply made full-feature Type-C cable. The full feature cables have to include more pins/wires, and are thus more expensive to produce.

 

[Elnrik]

USB type c is just the physical connector it has nothing to do with the usb 2.0 or 3.0 so you might as well by the fastest ones

What we do need to worry about is whether or not the cable itself supports charging at 3A 5v

Technically incorrect, but essentially right.

Assuming both cables adhere to standards, the Cable Matters USB 2.0 Type-C cable is (most likely) missing the data pins & wires needed to transfer at the rated Type-C 10GB/s speeds; however, it should still have all of the power pins and wires to charge at 5V 3A. The J&D cable, presumably being a full-feature cable, should support full Type-C power (100W) and data (10GB/s) speeds, and will also charge a Nexus at 5V 3A.

 

[toyanucci]

Technically incorrect, but essentially right.

Assuming both cables adhere to standards, the Cable Matters USB 2.0 Type-C cable is (most likely) missing the data pins & wires needed to transfer at the rated Type-C 10GB/s speeds; however, it should still have all of the power pins and wires to charge at 5A 3A. The J&D cable, presumably being a full-feature cable, should support full Type-C power (100W) and data (10GB/s) speeds, and will also charge a Nexus at 5V 3A.

So for just charging it would make sense to get the better constructed cable based on your observations?

 

[kibmikey1]

At this point, it's more about the cable you use than the charger. Using a backwards 3.0/3.1 compatible C to A cable will get you the same speeds as a standard C to C cable in USB use. The chargers coming standard with the phone are C to charger, so Google seems to be indicating separate charging and USB use here. However, compatible untethered chargers are available in both the Google stores and elsewhere. Just make sure if you're not buying the Google charger, you get one with the right specs.

 

[toyanucci]

At this point, it's more about the cable you use than the charger. Using a backwards 3.0/3.1 compatible C to A cable will get you the same speeds as a standard C to C cable in USB use. The chargers coming standard with the phone are C to charger, so Google seems to be indicating separate charging and USB use here. However, compatible untethered chargers are available in both the Google stores and elsewhere. Just make sure if you're not buying the Google charger, you get one with the right specs.

Yh, I;m still waiting for charging bricks with the correct specs but would just get the 6.6 ft cable from now.

 

[Glitch4583]

Worst case would be it sends 12V at 3A (36W) to your phone and your Nexus dies in a exploding lithium maelstrom of fiery chaos.

Leave it to Android to steal more features from the iPhone....

 

[heleos]

snip

So, if I read your post correctly, (very good post btw), if I were to buy a charger for work, I should try to find a USB-c to USB-c cable (5V/3A), and a USB-c wall plug, because the USB-c standard is what gets you the 15W? Using a USB-c to USB-a cable, even if it was rated for 3A, would max out at 10W?

Sent from my SM-G900V using Tapatalk

 

[Elnrik]

At this point, it's more about the cable you use than the charger.

This is a bit misleading, and while I see what your point is, I urge caution using such general statements. A one amp charger with a Type-A port, a computer's USB 2 port, a USB 3.1 port, and a Type-C port connected to Type-C adaptors will all produce different charging rates for attached USB Type-C devices.

 

[Elnrik]

So for just charging it would make sense to get the better constructed cable based on your observations?

I'm the type who thinks it's better to get the better constructed everything. So I'd look for a "USB 3.1" compatible C to C cable that was built well.

 

[kibmikey1]

This is a bit misleading, and while I see what your point is, I urge caution using such general statements. A one amp charger with a Type-A port, a computer's USB 2 port, a USB 3.1 port, and a Type-C port connected to Type-C adaptors will all produce different charging rates for attached USB Type-C devices.

True, but I was talking about USB transfer speeds, not USB charging speeds, since Google seems to be indicating separate charging and USB connectivity use with these phones, as evidenced by them including separate chargers and cables with them. Actually, only the 6P has both, the 5X only has the tethered charger.

 

[Elnrik]

So, if I read your post correctly, (very good post btw), if I were to buy a charger for work, I should try to find a USB-c to USB-c cable (5V/3A), and a USB-c wall plug, because the USB-c standard is what gets you the 15W? Using a USB-c to USB-a cable, even if it was rated for 3A, would max out at 10W?

Sent from my SM-G900V using Tapatalk

Yes, exactly.

Edit: According to what I've read, anyway. There might be something about 3.1 Type A ports that I'm not aware of which will allow 15W power. I know the 3.1 Type A port has extra pins. Just haven't been able to find in the 3.1 spec sheet a 100% absolutely for sure explanation either way. The Type-C specs pretty clearly spell out power states though, so I'm going to continue going by that. See attachment.

Second Edit: No, it would max out at 15 watts. The current I in amps (A) is equal to the power P in watts (W) divided by the voltage V in volts (V):

I = P / V.
3.0 Amps = 15 Watts / 5 Volts.

 

[Elnrik]

Or just buy a hard wired type-c charger like the one on the play store.

https://store.google.com/product/usb_c_charger

It won't power 100w, but I'm sure someone makes one that will.

 

[seezar]

Or just buy a hard wired type-c charger like the one on the play store.

https://store.google.com/product/usb_c_charger

It won't power 100w, but I'm sure someone makes one that will.

It's currently sold out. They also have a 60W version with a 12' cable but it's $59.

 

[Elnrik]

Ouch that's a bit pricey!

 

[[hfm]]

So, if I read your post correctly, (very good post btw), if I were to buy a charger for work, I should try to find a USB-c to USB-c cable (5V/3A), and a USB-c wall plug, because the USB-c standard is what gets you the 15W? Using a USB-c to USB-a cable, even if it was rated for 3A, would max out at 10W?

Sent from my SM-G900V using Tapatalk

Why not just get the 15W charger Google sells?

---------- Post added at 09:48 PM ---------- Previous post was at 09:47 PM ----------

It's currently sold out. They also have a 60W version with a 12' cable but it's $59.

Ooh man.. Good thing I loaded two of them into my pre-order. Almost everything I pre-ordered is sold out.