1 Reply Latest reply on Sep 26, 2020 7:04 AM by ShifangZ_26

    Problem with alt-mode state-machine in CCG4




      We are seeing some strange behaviour on our USB-C dock, more or less based on the CCG4 dock ref-design. Sometimes (maybe every 20th time) alt-mode fails to negotiate and based on the PD-signalling it looks it is the CCG4 alt-mode state-machine that fails. There might maybe be an underlying hardware problem (maybe I2C communication to mux or something), but a bit hard to understand how the alt-mode state-machine will change behaviour based on this.


      I have attached two traces. dp_alt_mode_failed the error is around line 179 were CCG4 sends NAK. In dp_alt_mode_failed_2 the error is in the last part (line 730 and below) CCG4 doesn't respond to "Enter Mode" sent from the sink. The other traces are successful attempt for comparison.


      Again, this is rather random occurrences so it might well be some timing or hardware stability issue, but maybe you can come up with some clues based on what external factors the CCG4 code will act on.