I have moded a PCB, with some additional wires to a connectors and switches.
The main PCB has a UART connection to a RF module(AVR+RF), where the main PCB would communicate to it, if its soldered on. In this case the module is not soldered on.
To acknowledge if this module is connected, i simple TX a "HELLO" and I would get reply "HELLO". I am aware that my reply message should be slightly different.
With the module not attached i am a still receiving a "HELLO". I have checked my PCB for any shorts, but this is negative.
Can noise cause such behaviour?