Debugging via USB while powered via battery?

Using Arduino General Electronics
1

Hello,

My application is using piezzo disk as a knock detector. The algorithm basically is looking for peaks when movement is detected in the piezzo. My issue is; I tested and debugged it using the serial port and it works well but as soon as I switch to battery power, I am getting strange results, most likely vref issues...

I normally plot the piezzo activity to see clearly what's going on but the issue is; as soon as I connect my USB cable, it is being powered from the USB's +5V and not the battery so everything looks OK. What I really want to do is observe the behaviour of the piezzo when it's powered by the battery to see what's the difference.

I made a USB converter where I am only connecting the data pins of the USB connector and power the MCU from the battery but then the serial port doesn't come up at all. Any idea would be much appreciated.

Thanks in advance.

2

Most people use a separate, commercial USB-serial adapter (like the FTDI adapter), and software serial for debugging. Only RX, TX and GND on the Arduino need to be connected to the adapter.

3

Have you also connected gnd?

Tom.. :smiley: :+1: :coffee: :australia:

4

Connecting GND as well solved my problem, thank you everybody!

5

Can you then click Tom's post as giving you the solution.