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Shorting the TX1+ and TX2+, RX1+ and RX2+, TX1- and TX2-, RX1- and RX2- in USB C

papaisou11

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Hello,

I am working on a project where I need to send I2C or, Analog Data between two PCBs (main PCB and Sensor PCB) using the TX and RX pins of the USBC conntector. The main PCB has a battery charger which will take input voltage from the same USBC connector. I am not willing to use additional polarity checking IC with the USBC port. For the I2C and Analog signals I am planning to use the free pins that is TX and RX. To support the polarity manually, I would like to connect (short) the RX1+ with the RX2+, TX1+ with the TX2+, RX1- and RX2-, TX1- with TX2- on the PCB. So that even though the user flip the USB C cable, the connection will remain the same.

Please see the below image where the shorted connection is highlighted using the same color.

1631696371742.png


My question is, will there be a problem if I connect this port of the main PCB using an USB type C to type C cord with the computer or other devices for charging?
 

KlausST

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Hi,

using a standardized connector with non standardized signals is always at your own risk.
What you are trying to do is against standards.

Thus I surely can not recommend this.

What I don´t understand: Why do you want to short several pins. I see no reason for it.
Why not using a single wire for each signal?

Klaus
 

FvM

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USB-C standard says related to alternate usage of the connector
Two requirements are specified in order to minimize risk of damage to the USB SuperSpeed transmitters and receivers in a USB host or device:
* When operating in an Alternate Mode and pin pairs A2, A3 (TX1) and B2, B3 (TX2) are used, these shall be AC coupled in or before the plug.
* Alternate Mode signals being received at the USB Type-C receptacle shall not exceed the value specified for VTX-DIFF-PP in Table 6-17 of the USB 3.1 specification
I'm not sure if shorting the SS pairs against each other inolves an additional risk of damage, I guess not, but the above constraints need to be considered in your design.
 

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