USB connector missing pins?  - Page 1
Forum section: electronics / projects

author: ricko_uk
author_rank: Super Contributor
timestamp: September 20, 2023, 01:53:29 am
content: Hi,A bit of a silly question...I would like to use this USB-C and Type A combo connector (but rinning USB 2.0 signals on both connectors):https://app.adam-tech.com/products/download/data_sheet/195877/usb-c31-a-d-vt-cs1-data-sheet.pdfBut it is confusing because the type C pinout has 14 pins (instead of the USB-C 12 pins) and most of them don't even match the USB-C pinout (also attached). That connector seems to have multiple GND and VCC (I assume the G = GND and V = VCC) but none of the other pins of the USB-C used by USB 3.0 are actually available? AM I missing something?USB 3.0 is not relevant for my design but I don't want to risk wiring it incorrectly.How do I connect the USB C part of that combo connector to a USB 2.0? Do I leave the CC1 and CC2 disconnected (I never design USB 3)?Anything I should generally be aware of using that type-C connector?Thank you

author: ataradov
author_rank: Super Contributor
timestamp: September 20, 2023, 02:51:50 am
content: You can see on the footprint drawing that USB A and C pins are completely separate. "A" are on the bottom in a row, and "C" are on the top. From the C part they only bring out D+/D-/CCx/VBUS/GND. This is enough for USB 2.0 mode.You will need 5.1 kOhm resistors to ground from both CC1 and CC2 if you are making a USB device. And connect D+/D- pairs together on the USB C side.But running the same signals on both is dangerous. You would have to be careful to not plug in both at the same time.And if you want USB host (assuming this is why you want USB A part), then you will need pull-ups on the CCx pins. If you want a dual role device on the USB C, then CCx signals need to be controlled in a special way and it is easier to get a special IC that would emulate a standard ID pin from the mini/micro-USB connectors.

author: ricko_uk
author_rank: Super Contributor
timestamp: October 10, 2023, 10:51:17 pm
content: Thank you @ataradov,I am going to keep two separate USB channels (one for each in the combo connector) to avoid the issue you mentioned. And they are both Host.For the USB-C (being only and always a host like the type A), I need to connect a 22K pullup to 5V as shown in the attached screenshot correct?Thank you

author: ataradov
author_rank: Super Contributor
timestamp: October 10, 2023, 10:56:58 pm
content: Host side needs 36 kOhm for 3.3V, or 56 kOhm for 5V.

author: ricko_uk
author_rank: Super Contributor
timestamp: October 10, 2023, 11:04:58 pm
content: Thank you @ataradov,Also I assume all the pins for both sides of the USB-C are connected with each other directly - also as shown in the attached schematic - correct?It is a bit of a stupid question but I never used type C and I want to make sure the only reason they expose twos sets of the same pins (just opposite orientation) is only to make it easy to manufacture the dual-row USB-C connector and not because of some USB electrical or functional requirement...Thank you

author: thm_w
author_rank: Super Contributor
timestamp: October 10, 2023, 11:16:32 pm
content: https://www.ti.com/lit/wp/slyy109b/slyy109b.pdfQuote

author: ataradov
author_rank: Super Contributor
timestamp: October 10, 2023, 11:24:00 pm
content: Quote from: ricko_uk on October 10, 2023, 11:04:58 pmIf you mean D+/D-, then yes, they must be connected on both sides. Only one side will be used depending on the cable orientation.

author: ricko_uk
author_rank: Super Contributor
timestamp: October 11, 2023, 12:17:27 am
content: Thank you @ataradov and @thm_w,Quote from: ataradov on October 10, 2023, 11:24:00 pmI assume also the CC pins must be tied together, not just the D+/D-. Right?Thank you

author: ataradov
author_rank: Super Contributor
timestamp: October 11, 2023, 12:47:13 am
content: No, CC pins are separate and each must have their own resistor.Just looked at the schematic, it is wrong. CCx pins should not be connected on either side. It will work with passive cables, but will mess up emarked cables.You can read about what happens when you short them herehttps://hackaday.com/2019/07/16/exploring-the-raspberry-pi-4-usb-c-issue-in-depth/(this is for the device side, but the same principle applies).

author: ricko_uk
author_rank: Super Contributor
timestamp: October 13, 2023, 07:22:23 pm
content: Thank you @ataradov