TCPP01-M12: How to read CC lines with ADC in 5V application
Hi!
I’m slowly working my way through a design in which I plan to use the TCPP01-M12; my device is a USB-C sink, and I don’t intend to utilize any USB-PD negotiation. I have a conflict with my chosen MCU and the UCPD peripheral (the pins of this peripheral need to be allocated to another use), so I am interested in being able to read the CC lines of the USB connection to understand the power capabilities of the upstream source, without dealing with any actual CC communication.
The datasheet for the TCPP01-M12 shows this exact use, on Page. 18, Figure 20. As I understand it, I can use my ADCs to read the voltages on the CC pins to calculate the current delivery capability of the source. What confuses me, however, is that apparently the source will also try to start communicating over the CC lines on connection. As I understand it, this communication happens at a logic level of between 0-1V or so, regardless of the actual current carrying capabilities.
The obvious problem is that if I sample the CC lines with my ADCs at the wrong time, I’d read invalid/incorrect voltage values, and have a false understanding of the source.
I’m finding it tricky to find resources that describe how I might be able to do this properly. I’m curious if anyone else has done this, and if so, how did the CC reading part of things work?
Thanks!