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Any type-C power source that meets the BC1.2 requirements may advertise BC1.2 on its D+/D- pins (independent of its type-C current advertisement via CC pins), but implementing BC1.2 is optional.
I would certainly expect dedicated chargers to implement it though since it costs literally nothing (BC1.2 advertisement for a dedicated charger is done by shorting D+ to D-) and it’s obviously desirable to support charging non-type-C devices (using an adapter cable) at a decent rate.
But it’s conceivable some might just forget to do this (or omit the USB2 D+/D- pins entirely), and BC1.2 signalling for a charging port that’s also used for data communication (a “charging downstream port”) is more involved hence probably more likely to be omitted.
Officially a USB-C device that needs more than default usb power is required to implement Type-C Current detection and only supposed to use BC1.2 (if implemented) as a fallback in the absence of 1.5A or 3.0A Type-C Current advertisement:
(from section 4.6 “Power”)
(from section 4.6.2.2 “USB Battery Charging 1.2”)
However… I see no harm in ignoring the CC pins (apart from the 5.1 kΩ pulldowns) and relying solely on BC1.2 since you’d be behaving exactly like a legacy USB device connected via a USB-C to USB-B cable.
I want to convert my USB charging port in my car to an USB C Port.
Now Im asking myself if I need to put the 5.1k Ohm resistors on CC1 and CC2.
I dont really know the specs of my car charger (its not that well documented).
So would it be safer to not include the resistors since the charger cant monitor the CC Pins so the max current is set to 100-500mA?
Or can I just add the resistors and let the connetcted device draw up to 3A (As I said I dont really know how many amps the charger can give)
The usecase for the Charger would be most likely 100% charging Phones.
for more intel.
The port was an USB 2.0 Port without any data connection to the car but it appears that the pins are (D- and D+ of the old USB 2.0 Connection) connected to an IC (RTQ2115AK) wich is an Charging Port Controller and Integrated 36V 3A Synchronous
Buck Converter
My question therefore is what do i do with the CC1 and CC2 connections I now have on the USB C Connectior I want to implement instead of the USB A female connector. By now I connected VCC GND and D+/- to the old pads. Wich appaers to work but it charges slowly. Thats why I came here to ask if I should the resitors and what to do with the other pins
Welcome to the DigiKey TechForum,
I’m not familiar with what is needed for this conversion.
Hopefully the one who posted the original article (@Kristof_2649), or one of the engineers can advise you on this.
I’ve posted a detailed explanation earlier in this comments section, but the short version is: pull the two CC pins up to 5V using 10 kΩ resistors (separate resistor for each CC pin) to advertise that your port can deliver 3A, or use 22 kΩ resistors to advertise that your port can deliver 1.5A.
I didn’t get any search results for RTQ2115AK, do you mean the RTQ2115A-QA ? You may want to check what the configured overcurrent protection limit of your charger is, which is set using a resistor connected from pin 1 (RLIM) to ground. The datasheet lists three values:
91 kΩ means 2.2 A ±15% (so that in case you should advertise 1.5A instead of 3A)
Update: I just noticed that as of May 2021 the USB Implementers Forum has a compliance update (#136) stating:
USB 2.0 and USB3.2 USB-C Products Operating as a Sink Must Billboard when Insufficient Power is Received to Power Up.
The USB Type-C Specification makes clear that alternate mode products and USB4 products must billboard. This update extends this requirements to USB 2.0 and USB 3.2 sink capable products that implement a USB-C connector
Which means that if a USB device which is a power sink requires more power to function properly than is advertised by the power source, it can’t simply keep itself fully switched off, it has to “billboard” which means to appear as a trivial usb device that implements the Billboard Device Class which just informs the host operating system “hey I’m <this type of device> but I can’t function right now because of <these reasons>”, so that the operating system can provide notice to the user why the device they plugged in isn’t working.
