The following steps show you how to setup Contiki Sniffer on Mac OS for 6LowPAN using CC2531 USB dongle in details.
1. Download pyserial-2.7.tar.gz and untar it by running "tar zxvf pyserial-2.7.tar.gz" under console terminal of Mac OS.
2. Install pySerial by running "sudo python setup.py install" under console terminal of Mac OS.
3. Download sensniff.py.
4. Download Contiki_Sniffer_CC2531EMK.hex to CC2531 USB dongle using TI CC Debugger and Flash Programmer.
p.s. If you want to use CC2538EM as sniffer, you have to set "#define CC2538_RF_CONF_SNIFFER_USB 1" in C:\contiki\platform\cc2538dk\contiki-conf.h and do make under "C:\contiki\examples\cc2538dk\sniffer". You will get sniffer.bin under "C:\contiki\examples\cc2538dk\sniffer" and flash is to CC2538EM using Flash Programmer 2.
5. Plugin CC2351 USB dongle or CC2538EM into Mac USB port and you should see it enum like /dev/tty.usbmodem1421. Please note that 1421 might be different from device to device.
6. Run "python sensniff.py -d /dev/tty.usbmodem1421 -b 460800" under console terminal of Mac OS.
p.s. CC2531 USB dongle needs you to press S1 or S2 button to make it work after you plug it into UAB port. I don't know why but if you cannot make it work, try it.
7. Download and install wireshark.
8. Run wireshark. Go to Edit->Preferences->Protocols->6LowPAN and add "aaaa::" to Context 0:.
9. Go to Edit->Preferences->Protocols->IEEE802.15.4 and check "TI CC24xx FCS format".
10. Go to Capture -> options -> Manage Interfaces -> New. Input /tmp/sensniff to "Pipe:" and save.
11. Start a new live capture on wireshark and enjoy it.