Proposal: Add GPS (TinyGPS++) and PMU (AXP2101) sensor modules

[khengari77]

Summary

This issue proposes adding two new sensor modules to OpenMQTTGateway:

1. GPS sensor module — reads NMEA data via TinyGPS++ over hardware UART or software serial
2. PMU sensor module — monitors AXP2101 power management chip (battery voltage, charging status, temperature, etc.)

These modules are designed for ESP32 boards with integrated GPS + LoRa + PMU (e.g., TTGO T-Beam), but are fully multi-platform (ESP32, ESP8266, AVR).

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GPS Module (sensorGPS.cpp + config_GPS.h)

• Supports hardware UART (0/1/2/3) and software serial fallback
• Configurable pins, baud rate, and read interval
• Publishes: satellite count, latitude, longitude, altitude, date, time
• Platform-aware pin defaults (ESP32, ESP8266, ATmega2560, Arduino Uno)

PMU Module (sensorPMU.cpp + config_PMU.h)

• AXP2101 initialization and configuration
• Voltage regulators for ESP32, LoRa, GPS power rails
• Battery monitoring: voltage, percentage, charging status, VBUS, system voltage, temperature
• Low-battery warning and shutdown thresholds
• Charging LED control, fuel gauge learning
• Interrupt-driven IRQ handling

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Both modules follow existing upstream conventions:

• .cpp files (not .ino)
• THEENGS_LOG_* macros for logging
• enqueueJsonObject() for publishing data
• #include "TheengsCommon.h" pattern
• GPLv3 license headers

The implementation is available in my fork for reference:
https://github.com/khengari77/TDOA-tracker/tree/development/main

Would the maintainers be interested in these additions? Happy to adjust based on feedback before submitting a formal PR.

[khengari77]

One clarification: my fork (khengari77/TDOA-tracker) is quite behind on upstream commits — it forked from the old .ino-era codebase. However, the GPS and PMU module code in the proposal has been refactored to match the current upstream conventions:

• .cpp extension (not .ino)
• THEENGS_LOG_* macros (not Log.*)
• enqueueJsonObject() (not handleJsonEnqueue())
• #include "TheengsCommon.h" pattern
• Updated GPLv3 license headers

So while the rest of the fork is outdated, these two modules are written to the latest standards and should integrate cleanly with the current development branch.