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hello im trying to make a usb receptacle for my microcontroller, im planning to use USB Type C, Although i only need USB 2.0 functionality i might as well design it to specification so that the mCu will work on any computer and any* possible cable configurations most importantly USB C - USB C and USB A-USB C.

https://www.allaboutcircuits.com/uploads/articles/Fig1m11292018.png

The receptacle i have is a 16pin(12 legs) one, I have shorted the redundant pins such as GND, VBUS, D- and D+. But i dont know what to do with SBU1, SBU2, CC1, and CCC2. What should i do to those pins? I would also want that the board will work with USBC PD power supplies. The board only needs the standard 5v 1A (500mA is fine).

I have read that CC needs a pull resistors but i do not know the exact value, or is it best just to leave it floating? Does the USB specification what to do on devices only needing USB2.0 functionality but is using a USB C receptacle?

enter image description here

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  • \$\begingroup\$ For USB data communication, a pull-up resistor on D+ is needed. However, many microcontroller have it built-in. So this question must be answered in a greater context. Please specify the microcontroller or whatever chip will be connected to D+/D-. \$\endgroup\$
    – Codo
    Sep 25 at 14:52
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I'm assuming that your board with a microcontroller will take on the role of a USB 2.0 device (as opposed to a host). If so, it needs to wired up like so:

  • Connect all GND contacts with each other
  • Connect all VBUS contacts with each other
  • Connect the D+ and D- pairs with each other (A6 to B6, and A7 to B7)
  • Leave SBU1 and SBU2 unconnected
  • Pull CC1 and CC2 down to ground with a 5.1kΩ resistor (separate resistor for each)
  • Pull D+ up to 3.3V with a 1.5kΩ resistor (unless your microcontroller already does so)

Update

The RP2040 microcontroller (and the Raspberry Pi Pico) can act both as a USB device and a USB host.

A host requires a 15kΩ pull-down resistor on both D+ and D- (instead of the pull-up resistor on D+). To achieve its flexibility, the RP2040 provides the pull-up and pull-down resistors for D+ and D- internally. They are activated depending on the USB role.

For the USB-C connector, additionally changes are needed for the host role. CC1 and CC2 should have a pull-up resistor of 36kΩ to 3.3V (or 56kΩ to 5V) instead of the pull-down resistors.

As a host, the Raspberry Pico can no longer draw power from the USB bus. Instead, it must have an independent power supply and provide power to the USB bus.

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  • \$\begingroup\$ The microcontroller is the RP2040 from raspberry pi, I have their [schematics] on their commercial board(datasheets.raspberrypi.org/pico/pico-datasheet.pdf) there seems to be no pull up resistors on the datalines just a series resistor on D+ and D-. Thank you for the complete checklist :) \$\endgroup\$
    – Jake quin
    Sep 26 at 1:16
  • \$\begingroup\$ I am curious though if my mCU board does act as a host what is needed to be done? \$\endgroup\$
    – Jake quin
    Sep 26 at 2:21
  • \$\begingroup\$ See my update re USB host mode. \$\endgroup\$
    – Codo
    Sep 26 at 8:33
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Take a look at USB Type-C specification. What you are trying to do is a Sink-only UFP, without PD. Look at Table 3-5 and Figure 4-5. In short:

  • Pull down each CCx pin to ground through a distinct 5.1 kΩ resistor,
  • Leave SBUx unconnected,
  • Short DPs, DMs, VBUS and GND pins by group.

Do what is specified by the MCU manufacturer for external pullup/downs on DP and DM, if any.

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  • \$\begingroup\$ Thanks, im sorry i cant mark your answer , since codo answered first. \$\endgroup\$
    – Jake quin
    Sep 26 at 1:34
  • \$\begingroup\$ Sure. No problem. I started to answer before his was posted, finished after. His answer is perfectly correct to me. Nothing to say :) \$\endgroup\$
    – Nipo
    Sep 26 at 8:51

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