USB-c data and pwr spliter - Page 1
Forum section: electronics / projects

author: rodrigopires
author_rank: Regular Contributor
timestamp: September 28, 2022, 01:25:50 pm
content: I need a USB-C data and power splitter to be able to connect my tablet to the charger and to ethernet. Bought a hub from Amazon but it does not allow to charge the device (data works ok) so I disconnected the wires and try to make a splitter myself. Now I have two USB-C female with 4 wires (GND, +5, D+, D-) and a USB-C male I cut from a phone cable with 5 wires (GND, +5, D+, D-, CC). My problem is how to get the tablet to accept charging and data at the same time? If I leave CC unconnected the tablet charges but does not have data connection, if I connect CC to GND via a 5.1k resistor I have data working, but it does not charge. How can I emulate, for example, a laptop connection where I can charge my phone at the same time transfer data? How should I connect CC?Note: I tried to charge the tablet with a USB cable without data pins (just GND and 5v) and it does charge (in slow charging mode).Photo in attachment resumes my setup

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 28, 2022, 01:52:16 pm
content: You'll have to implement USB-PD to tell the tablet to stay in USB host mode while accepting power.An alternative is to implement networking with the tablet in device mode.https://github.com/Genymobile/gnirehtet

author: rodrigopires
author_rank: Regular Contributor
timestamp: September 28, 2022, 02:33:50 pm
content: In order to do that, what should I do to the CC wire?

author: ajb
author_rank: Super Contributor
timestamp: September 28, 2022, 04:29:59 pm
content: What sort of tablet? Like a tablet PC running a desktop OS, or a mobile device running Android or whatever?It's going to be FAR easier to just get a hub or docking station that allows pass-through charging and provides an ethernet connection, there are tons of those out there at a range of price points and feature sets. However, I don't know if mobile devices will support a lot of them--certainly if the dock includes a display adapter then that requires specific support on the tablet side of things that I'm not sure is common.USB charging is a lot more complicated nowadays than when it first started to become common. USB-PD and USB-C allow for ports with multiple roles (power source or sink, host or device, charging only, or a combination) and up to 20V at a range of different currents, and all of that has to be negotiated between the two devices. If you get this wrong it would be very easy to apply 20V to a device that can't handle it--especially here, where you're trying to piggyback a USB network adapter that will certainly not be happy with more than 5V onto a charging connection. The right way to do this is to implement the proper negotiation circuitry in the port facing the tablet and in the port facing the charger, and whatever the charging port negotiates with the charger needs to be communicated to the tablet port so that it knows what it can offer the tablet.

author: ejeffrey
author_rank: Super Contributor
timestamp: September 28, 2022, 07:32:43 pm
content: You basically can't do this correctly simpler than a USB hub with pass through charging. Note that USB-C has no "5V" pin, that is a misnomer. USB-C does not supply any voltage to the Vcc pin until it negotiates with either the remote USB-C device or detects a USB-C->B cable, and it can negotiate from 5 to 20V. Also, USB type C cables that support super speed need an electronic ID tag on the cable, otherwise they won't support superspeed. In addition, the ethernet device will need to separately negotiate the current limit on it's supply, either via USB type C detection or through the legacyAn example:https://www.amazon.com/uni-Charging-Thunderbolt-Aluminum-Pixelbook/dp/B08SVZFFPP/Note that this only has USB type A downstream ports, so your network device would need to be USB-A or connected with an adapter. Many monitors with USB-C ports also have laptop charging capability. This device basically does correctly what you want to do: it passes through USB-C power delivery from the power brick, while separately supplying 5VDC to the downstream type A ports.

author: spostma
author_rank: Regular Contributor
timestamp: September 28, 2022, 09:35:37 pm
content: AliExpr item 1005002198734869 Baseus USB-C docking station should be what you need:- 60W USB-C Power Delivery- 3x USB3- 4K HDMI- 1000mbps EthernetYou also need USB-C power adapter (preferrably a USB-C PD 65W GaN Charger line Ali 1005003891797309)and an USB-C cable of course

author: rodrigopires
author_rank: Regular Contributor
timestamp: September 29, 2022, 07:56:50 am
content: Quote from: ajb on September 28, 2022, 04:29:59 pmThe tablet is a Lenovo running android 10, and it only has one USB-C port and I need it to have wired ethernet and to be charging at the same time.Quote from: ajb on September 28, 2022, 04:29:59 pmYes, I now know that, but I don't mind the slow charging I get just with 5v connected (no CC) it seems to be enough. But I can manage to get only data, or only charging and I need both at the same time.Since I already bought the adapter and have the connectors in hand tried to do it. I have seen some people that have done it (https://cdn.hackaday.io/files/262631123636192/pd-buddy-wye.pdf) but they had CC wires on the female plugs to connect to the output and my wires don't have it so I'm left without reference.

author: spostma
author_rank: Regular Contributor
timestamp: September 29, 2022, 01:31:21 pm
content: then AliExpress item 1005004646491127 should be what you need for $1,40:a 1 to 2 Type-C Splitter USB C Male to Dual USB C Female Extension Connector.Not only for charging, but also can transfer data:one USB C female Port for data and charging,another Port only with charging function.