After modifying all pio settings to allow for Ublox GPS alternative, defaults to L76k; TODO code to implement Ublox

docs/pio.md

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+# pio
+pio stands for "PlatformIO".  
+
+In your context (ESP32 / T-Beam / PlatformIO workflows), **“pio” stands for:**
+
+> **PlatformIO**
+
+More precisely, `pio` is the **command-line interface (CLI)** for the PlatformIO environment.
+
+---
+
+## What PlatformIO is (practically speaking)
+
+PlatformIO is an embedded development framework that wraps:
+
+* toolchains (GCC for ESP32, ARM, etc.)
+* build system
+* library manager
+* uploader (esptool, etc.)
+* serial monitor
+
+So instead of juggling:
+
+```bash
+xtensa-esp32-elf-gcc
+esptool.py
+arduino-cli
+```
+
+…you use:
+
+```bash
+pio run
+pio run -t upload
+pio device monitor
+```
+
+---
+
+## What `pio` actually does in your workflow
+
+Given your T-Beam usage (as shown in the LilyGO docs, which explicitly include PlatformIO as a supported environment ), `pio` is orchestrating:
+
+### Build
+
+```bash
+pio run
+```
+
+* compiles your firmware using the environment in `platformio.ini`
+
+### Upload
+
+```bash
+pio run -t upload
+```
+
+* invokes the correct uploader (ESP32 → `esptool`)
+* uses the selected `/dev/tty*` device
+
+### Monitor
+
+```bash
+pio device monitor
+```
+
+* serial console at configured baud
+
+---
+
+## Why it exists (the “systems view”)
+
+PlatformIO abstracts away:
+
+* board definitions
+* pin mappings
+* compiler flags
+* library dependencies
+
+In your `platformio.ini`, for example:
+
+```ini
+[env:node_a]
+platform = espressif32
+board = esp32-s3-devkitc-1
+```
+
+That single block drives:
+
+* toolchain selection
+* linker scripts
+* upload protocol
+* memory layout
+
+---
+
+## Important nuance (since you’re working low-level)
+
+`pio` is **not**:
+
+* a compiler
+* a flasher
+* an IDE
+
+It is a **build orchestration layer** (think “make + package manager + uploader + board database”).
+
+---
+
+## Quick mental model
+
+If we translate to Unix analogies:
+
+| Concept             | Analogy                                      |
+| ------------------- | -------------------------------------------- |
+| PlatformIO          | `portage + make + gcc + flash tool` combined |
+| `pio run`           | `make`                                       |
+| `pio run -t upload` | `make install` (but to hardware)             |
+| `platformio.ini`    | hybrid of `Makefile` + config                |
+
+---
+
+## Bottom line
+
+When you type:
+
+```bash
+pio run -t upload
+```
+
+You are saying:
+
+> “Use PlatformIO to build this firmware for the specified environment and flash it to the target device.”
+
+