The physical layer devices are responsible for decoding the raw bit streams from the medium. In general, you can not access the data of the network until it is packaged into frames at the link layer. For that you can look at a tool that uses some form of the pcap library (tcpdump/wireshark).
To get at the actual 'bits on the wire' you will likely have to alter the device drivers for your particular system; there isn't going to be a universal library to do this as each system implements things differently.
My original posting would have included mildly insulting remarks about the needlessness of trying to do Layer 1("You're doing it wrong" and "These are not the droids you're looking for"). I even thought about including a link to some microcontroller websites (and ContikiOS now that I think about it) so he could get down to the bare metal. But then I realized, no, none of that would have been helpful.