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I am working on a project which connects a microcontroller to an IR sensor device and decided to use a male-male USB C since I need 5 lines (V,GND,SCL,SDA,ADC).

Which pin should I use for my single-ended analog line? Im guessing the SBUS audio line in Fig.2 (minimizing cross-talk and EMI interference)

Also which should I use for my SDA and SCL lines?

fig1

Fig.1

Fig.2

Fig.2

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  • \$\begingroup\$ Do you have any specific concerns about EMI/Interference? Or just trying to minimize any potential impact it has? Crosstalk is much more likely to be an issue than EMI (unless your environment is harsh). Some cables have a secondary internal shield for the high-speed signals (which may be what that second black circle in Fig.2 is). If that's the case, simply put the analog signal inside the shield, and the digital lines outside the shield. If not, you could create a makeshift shield by putting analog on one end of the wire, digital on the other, and grounding everything in between. \$\endgroup\$ – Platytude Jan 11 at 0:17
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It sounds like you want to use the USB Type-C connector for totally proprietary interface, and take advantage of having quality-built standard full-featured USB cables. Sounds reasonable to me. But since the cable doesn't have a key and can be plugged in both ways on both ends of your interface, you have to be smart how to use the wires.

The choice for your power "V" and ground is obvious - VBUS and GND.

Then, since you don't know how a particular cable is constructed inside for SS links (either 8 micro-coax or 4 twisted pairs), you should use them in "pseudo-differential" way, say connect your analog ground to Tx1-, and the signal to Tx1+. Same for SCL and SDA. For symmetry I would use D+ and D- for analog signal (it will be double shielded), and use Tx1(+,-) and Rx1(+,-) for I2C signals.

Now it is up to you to make parallel (cross) connections on your microcontroller (receptacle) side and sensor receptacle side, so that the cable orientation won't matter in all four variants.

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