It seems that my G120 needs a press on the RESET to start up the Debugger interface after applying the USB cable.
Is this on purpose?
EMX just shows the debugger automatic in the same configuration.
most likely the application resident on the board is in a tight loop or an exception is occurring. use mfdeploy to erase the application and see if the problem disappears.
It is doing the same on a fresh board without an app.
It seems that the G120 in this case will not start before reset is pressed.
This is the case both for the application and the debugger.
After turning on the power is must have a reset to run.
Any idea why?
Solution:
- A pull-up resistor on the on the reset pin to +3.3V (Vcc)
- A 1 uF capacitor from the reset pin ground (parallel with the reset button)
This ensures that the reset pin is released a fraction of time after the power goes on.
always helpful to say you are asking a question about a custom board. 
G120 can be on a custom board, only 
OK - you have a point.