Reset powers down my USB Port!

I recently had a question from a customer who had purchased TinyTimer KS and was concerned that when they pressed the reset button it would power down the USB Port on the computer.  This post addresses what is going on and why that happens.

In the Arduino environment reset generates a condition that looks like a short.  Essentially it drops the voltage to the chip and causes a reset.  In the PC environment the USB bus is designed to protect the components connected.  So when a device shorts out its port is powered off by the computer to protect the USB bus.

When the same Arduino compatible device is connected to a “dumb” USB power source such as a wall charger, the reset works as expected.

The takeaway here is that you should avoid using reset while connected to USB on a computer.  Instead, just unplug the device and plug it back in when using a computer for power.

 

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