I'm looking to use USB C in my schematic but instead of using USB3.1 data line I would like to use USB2.0 data line. This device is on the receiving end and already have internal power so do not need power from the host. My question would be beside connecting to pull down resistor, do I need to connect CC1 and CC2 to microprocessor?
\$\begingroup\$
\$\endgroup\$
1
-
\$\begingroup\$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. \$\endgroup\$– Community BotCommented Sep 17, 2021 at 23:21
Add a comment
|
2 Answers
\$\begingroup\$
\$\endgroup\$
2
Since you are a UFP (Upstream Facing Port), two 5.1K resistors to ground should be enough. You need one 5.1K resistor on the CC1 line and one 5.1K resistor on the CC2 line. You don't need to connect those lines to anything else. Just be sure you don't short them together and make the same mistake the RPi guys did (see: https://www.scorpia.co.uk/2019/06/28/pi4-not-working-with-some-chargers-or-why-you-need-two-cc-resistors/)
However, since you are providing your own power, I do believe that you need to be careful with your design such that you don't source current back on the D+/D- lines if the host goes into suspend/sleep modes.
Good luck.
answered Sep 18, 2021 at 5:15
-
\$\begingroup\$ Thanks for your input! For my understanding, CC1 will communicate via biphase mark encoding to do the handshaking (Source: youtube.com/watch?v=V1OiQoyjDOo around 20:30 time frame). In that case, do I need anything in the middle to decode that message to send it to the processor? Or that's only needed if using high-speed 3.1? \$\endgroup\$ Commented Sep 19, 2021 at 4:25
-
\$\begingroup\$ Communication is only required if you want to negotiate to pull more than 5V at 900mA. Otherwise, the resistors are just fine. \$\endgroup\$ Commented Sep 20, 2021 at 23:29
\$\begingroup\$
\$\endgroup\$
1
From USB C specifications:
For the device, the location of the USB SuperSpeed data bus, USB 2.0 data bus, CC and VCONN pins are fixed by design. Given that the device pin locations are fixed, only two possible connected states exist when viewed by the host.
In the case of a USB 2.0 device, using a USB Type C connector only CC1 must be connected to the pull down resistor. VCONN (CC2) can be left floating.
-
\$\begingroup\$ Hi, Thanks for writing an answer. Please see this site rule from the help center which explains that when you include any content from elsewhere (e.g. photo, image or text) into a post here, you must add a proper reference, which includes a link back to the original web page. Therefore please can you edit your answer ASAP to include the source link for the image which you copied into this answer. I recommend that you also read the tour and the rest of the help center, to see the main site rules. Thanks. (After you have correctly added the reference, I can remove this comment.) \$\endgroup\$– SamGibson ♦Commented Oct 18, 2022 at 13:33