129 lines
2.4 KiB
Markdown
129 lines
2.4 KiB
Markdown
# Raspberry Pi Pico W – Minimal Wi-Fi UDP Example (Arch Linux)
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## Authorship
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This document was generated using ChatGPT (OpenAI), version 5.2.
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It has not been independently reviewed or validated yet.
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## Purpose
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Minimal Pico W Wi-Fi example using the Arch Linux packaged Pico SDK.
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Goal: clean build, no hidden assumptions, raw lwIP usage.
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---
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## Environment
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* Arch Linux
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* `pico-sdk` from `/usr/share/pico-sdk`
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* Board: Pico W
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* Toolchain: `arm-none-eabi-gcc`
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* lwIP in `NO_SYS` mode
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* Driver: `pico_cyw43_arch_lwip_poll`
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---
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Add the following sections.
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---
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## Build
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```sh
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mkdir build
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cd build
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cmake ..
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make -j
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```
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Explanation:
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* `cmake ..` configures the project and generates build files.
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* `make -j` builds using all available CPU cores.
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* After configuration, normal source changes require only `make -j`.
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* If `CMakeLists.txt` changes, delete the `build/` directory and run `cmake` again.
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The resulting firmware file:
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```
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build/pico_w_udp_client.uf2
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```
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---
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## Flash
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```sh
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picotool load -f pico_w_udp_client.uf2
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```
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This writes the UF2 image to the Pico W over USB (device must be in BOOTSEL mode or rebooted via picotool).
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---
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## Runtime Behavior
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After flashing and reset:
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1. The Pico W connects to the configured Wi-Fi network.
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2. Once DHCP assigns an IP address, the onboard LED turns on.
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3. The device begins sending periodic `hello world` UDP messages to the configured destination IP address.
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## CMake Configuration
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Board is selected in `CMakeLists.txt`:
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```cmake
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set(PICO_BOARD pico_w)
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include(pico_sdk_import.cmake)
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```
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Wi-Fi credentials are kept outside the main source tree:
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```cmake
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target_include_directories(pico_w_udp_client PRIVATE
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${CMAKE_CURRENT_LIST_DIR}
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${CMAKE_CURRENT_LIST_DIR}/../secrets
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)
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```
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Example usage:
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```c
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#include "secrets/fra.h"
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```
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This keeps credentials separate from firmware logic.
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---
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## Networking Model
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* lwIP raw API (UDP)
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* `NO_SYS = 1`
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* Explicit polling via `cyw43_arch_poll()`
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* Project-local `lwipopts.h`
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No sockets, no netconn, no `sys_arch`, no background threads.
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---
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## Key Points
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* Arch SDK requires providing your own `lwipopts.h`.
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* Sockets require `NO_SYS = 0` and a `sys_arch` implementation — not used here.
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* Raw API is the simplest and fully self-contained option.
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* TCP/UDP framing must be handled at application level.
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---
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## Result
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✔ Builds cleanly
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✔ Pico W connects to Wi-Fi
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✔ UDP packets transmitted
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✔ Deterministic configuration
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