Elizabeth, I’ve never understood why some people put resistors in shorting plugs for analog inputs. As I mentioned earlier in the thread, from the perspective of the input circuit a plug providing a direct short would be little different than if the input were connected to a powered up component having very low output impedance, that is not providing a signal.
Hal, I’m not particularly familiar with the design of integrated circuit chips which provide USB interfaces, but I suspect that what you read to the effect that USB inputs should not be shorted is correct. First, USB interfaces are bidirectional, with communications occurring in both directions on the same differential pair of signal lines when something is connected that can be communicated with. So a USB "input" is also an output. Second, I believe such chips are designed to pull those lines to certain voltages when nothing is connected to them, via internal resistors, and shorting them may affect those voltage states in adverse and/or unpredictable ways. So I would recommend against doing that.
Best regards,
-- Al
Hal, I’m not particularly familiar with the design of integrated circuit chips which provide USB interfaces, but I suspect that what you read to the effect that USB inputs should not be shorted is correct. First, USB interfaces are bidirectional, with communications occurring in both directions on the same differential pair of signal lines when something is connected that can be communicated with. So a USB "input" is also an output. Second, I believe such chips are designed to pull those lines to certain voltages when nothing is connected to them, via internal resistors, and shorting them may affect those voltage states in adverse and/or unpredictable ways. So I would recommend against doing that.
Best regards,
-- Al