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transmitter

README.md

Compile: gcc backscatter-tx.c -lpcap -lczmq -lzmq -o inject

Transmit: sudo ./transmit.sh

RPi Hardware and Software Setup

Install Kali Linux on the Raspberry Pi. Configure the Ethernet interface to use a static IP address, so it'd be easier to find the RPi when connecting it directly to your Mac.

Connect Port D4, D5 on radio board to Port D0, D1 on MCU board. This passes downlink resolution control to the camera.

Config details for our own Pie:

  • IP Address: 192.168.0.38
  • SSH Server: Port 22
  • Username: root
  • Password: toor
  • TP-Link Interface: wlan1, wlan1mon (monitor mode)
  • The on-board WiFi interface has been disabled to prevent interference

Connect RPi to the Internet

  1. install squid on your mac (brew install squid). The default config works well.
  2. exec squid (there may be firewall prompts)
  3. on RPi, exec export https_proxy=http://<YOUR_MAC_LAN_IP>:3128 and export http_proxy=http://<YOUR_MAC_LAN_IP>:3128
  4. the current shell session is now configured to use the proxy on your mac (do this every time when starting a new shell session, or just put it in shell rc file)

Install Deps

Install the following deps:

- libzmq3-dev
- libczmq-dev
- libpcap-dev

Compile the code

To compile, exec gcc backscatter-tx.c -lpcap -lczmq -lzmq -o inject

Run the injection

  1. Set up the interface. On Intel NUC, use setup_inject.sh. On RPi, use setup.sh. You may need to modify backscatter-tx.c to use the correct monitor interface.
  2. exec inject

Test

By default, the inject program will transmit excitation packets. It also opens a zmq port and basically transmits all data received on that port. To test this function and send downlink message, install additional deps:

  • python3-dev
  • python3-pip
  • pkg-config
  • zmq (install via pip3)

When inject is running, start the test script by executing python3 downlink-test.py.