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Raspberry Pi Pico W Nexmon Applications

Applications for the Raspberry Pi Pico W related to WLAN firmware patching for the bcm/cyw43439a0 using Nexmon: The C-based Firmware Patching Framework for Broadcom/Cypress WiFi chips.

Applications

AppDescription
dump_rom<sup>1</sup>Read ROM content from WLAN SoC and hex dump it to Pico's console.
dump_console<sup>1</sup>Read WLAN SoC's ARM core internal console and dump it to Pico's console.
ioctl_test<sup>2</sup>Write string via IOCTL to SoC's internal console, read back internal console, and dump it to Pico's console.

<sup>1</sup> Works with unmodified firmware provided by cyw43-driver.
<sup>2</sup> Requires firmware that implements the NEX_WRITE_TO_CONSOLE IOCTL, uses this patch by default.

Setup

There are various standard setups that allow working with a Raspberry Pi Pico W. Our setup exists of a single Raspberry Pi Pico W powered over USB and a Raspberry Pi Debug Probe. The Debug Probe is connected to a Linux host system via USB and to the Pico's UART Serial and SWD Debug ports, as described here. The applications provided here do not depend on the setup around your Pico W, hence, if you are running into general setup problems, please consult the official documentation and getting started guides for the Raspberry Pi Pico (W): documentation page.

Getting started

  1. Clone this repository, and check out submodules (cyw43-driver): 
    git clone --recursive https://github.com/seemoo-lab/pico-nexmon.git
  2. Patch submodules: 
    cd pico-nexmon
chmod u+x script/patch && script/patch
  3. Setup Raspberry Pi Pico SDK:
    • This repository depends on the pico-sdk. We recommend to head over to the pico-sdk repository, create a working setup by following its README, and build and try at least some of the pico-examples for the Pico W before continuing here.
    • If you have a working Pico SDK and Pico W setup, ensure that the environment variable PICO_SDK_PATH is set to the SDK's root before calling CMake, or directly pass the SDK location to CMake with -DPICO_SDK_PATH=<path to pico-sdk>.
  4. Setup Nexmon:
    • You might skip setting up Nexmon, if you are only interested in the dump_rom and/or dump_console applications. In this case, provide -DNO_NEXMON=1 to CMake.
    • If you already have a working copy of the Nexmon framework, ensure that the environment variable NEXMON_ROOT is set to the framework's root before calling CMake, or directly pass the framework location to CMake with -DNEXMON_ROOT=<path to nexmon>.
  5. Build the applications:
    1. Create and enter build directory. 
      mkdir build && cd build
    2. Use CMake to build the targets of your choice. Below are a couple examples:
      • Example A) PICO_SDK_PATH and NEXMON_ROOT directly provided to CMake, build all applications: 
        cmake -DPICO_SDK_PATH=<path to pico-sdk> -DNEXMON_ROOT=<path to nexmon> ..
make
      • Example B) PICO_SDK_PATH and NEXMON_ROOT set as environment variables, build all applications: 
        export PICO_SDK_PATH=<path to pico-sdk>
export NEXMON_ROOT=<path to nexmon>
cmake ..
make
      • Example C) PICO_SDK_PATH set as environment variable, do not use nexmon, build all applications that do not depend on nexmon: 
        export PICO_SDK_PATH=<path to pico-sdk>
cmake -DNO_NEXMON=1 ..
make
      • Example D) PICO_SDK_PATH directly provided to CMake, do not use nexmon, build only dump_rom application: 
        cmake -DPICO_SDK_PATH=<path to pico-sdk> -DNO_NEXMON=1 ..
make picow_dump_rom
  6. Load and operate the application of your choice on your Raspberry Pi Pico W:
    • This step depends on your setup. Please follow the official instructions from Raspberry Pi's documentation and getting started guides that match your setup.
    • One example that works with our setup is to listen to the UART output using minicom and load the dump_console application with openocd as follows: 
      minicom -b 115200 -o -D /dev/ttyACM0

      openocd -f interface/cmsis-dap.cfg -f target/rp2040.cfg -c "adapter speed 5000" -c "program dump_console/picow_dump_console.elf verify reset exit"

Quickstart

We provide scripts that automate the setup of pico-sdk, openocd, minicom, and nexmon on Ubuntu 22.04.3 LTS machines. Just copy and paste the following:
We tested the scripts on a VM running Ubuntu Server 22.04.3 LTS. They probably work on other versions and distributions too, but this is up to you to find out.

sudo apt update && \
sudo apt install -y git && \
git clone --recursive https://github.com/seemoo-lab/pico-nexmon.git && \
cd pico-nexmon && \
./script/patch && \
./script/setup_pico && \
./script/setup_nexmon && \
source ~/.bashrc

Once the setup is done, you might built all applications by executing the following:

mkdir build && \
cd build && \
cmake .. && \
make

For an example on how to use the applications check out step 6 of the getting started section.

Contact

Jakob Link <jlink@seemoo.tu-darmstadt.de>

Reference the pico-nexmon project and the nexmon project:

Any use of this project which results in an academic publication or other publication which includes a bibliography should include a citation to the pico-nexmon project and the Nexmon project:

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Secure Mobile Networking Lab (SEEMOO)

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Multi-Mechanisms Adaptation for the Future Internet (MAKI)

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Technische Universität Darmstadt

TU Darmstadt