UART Signal Change


Hello Sierra Wireless World,

i have a question about the Signalchange Event while working with UART

My modem works in Nullmodem role. I want to read periodically from a microcontroller, but I have only TX,RX and Ground. For this one I turned off the flow control.

My problem is that i get Signal changes as you can see in my Traces.

Can anybody help me? Why do I get this state changes?

Thank you all



When a particular flow like UART is accessed using Open UART interface,then if UART_CB_ON_SIG_STATE_CHANGE notification is fired then the corresponding callback i.e. signal state change event handler is called. In this handler, signal state change is handled which gives the information about which signal is changed and the state of the signal for the UART. That is the reason, in the traces, Signal change is seen.