Hi Francois, I assume that _ioctl(uart_dev, HDLC_SETIFNET, NULL); should be sufficient to disable HDLC and allow normal UART communication. _ioctl(uart_dev, HDLC_SETIFNET, ppp_dev); should re-enable the HDLC interface. Please let me know if this works or not. Harald P.S. Sorry for not answering this sooner.