So I’m trying to figure out what signal on what pin switches the Switch from screen to TV out. I got a switch that didn’t boot and on investigation the P13USB had popped and the track under pin 22 (SBU1) had burned out.
I replaced the Pi3USB and ran a jumper from pin 22 to the filter. The Switch now boots and charges as normal however it doesn’t dock.
I have check the continuity from the USB C port to all the parts on the motherboard, using a USB-C breakout board, and this all seems fine.
I’ve check the 3v going into the Pi3USB and these are all present. I’ve checked the diode values around the Pi3USB and they all seem to be within spec.
I’ve checked the filters and these all seem good along with the caps just above them.
When I try to dock the switch the on board screen goes blank but the TV doesn’t see any signal from the dock. I’ve also tried a HDMI dongle and swapping it 180 degrees I still get nothing.
With just a 5v power supply attached I see 1.8v on pin 22 (SBU1) and with a HDMI dongle this goes to 0v and I see 3v on pin 21 (SBU2)
What I would like to know is what is the difference between a power supply and a Dock/HDMI dongle plugged in? What signals change on the USB-C port. I know the CC lines may swap but that depends on which way the power supply is plugged in.
Anyone got any insight?