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v1.9.5 - ADC Millivolt Conversion Support (2025-11-28)

What Changed?

This release adds optional hardware calibration-based ADC to millivolt conversion using ESP32's analogReadMilliVolts() function. Users can now output both raw ADC values (0-4095) and converted millivolt values (0-3300mV) for accurate voltage measurements. The feature is compile-time optional with zero overhead when disabled.

What's New

Main Feature: ENABLE_ADCMV Flag for Dual ADC Output

What it does: Adds a compile-time flag (ENABLE_ADCMV) that enables hardware calibration-based ADC to millivolt conversion. When enabled, detection events include both adc_raw (raw 12-bit ADC value) and adc_mv (converted millivolt value using ESP32's built-in calibration table).

How to use it:

Development environment (enabled by default):

task dev:build    # ENABLE_ADCMV=1 enabled

Production with dual ADC output:

PLATFORMIO_BUILD_FLAGS="-DENABLE_ADCMV=1" pio run -e esp32dev-release

Production default (single ADC value):

pio run -e esp32dev-release    # ENABLE_ADCMV=0 (no overhead)

Code example:

// In config.h - compile-time flag (default: disabled)
#ifndef ENABLE_ADCMV
#define ENABLE_ADCMV 0    // 1=enabled, 0=disabled (default)
#endif

// In sensor_data.h - conditional fields
#if ENABLE_ADCMV
  uint16_t adc_raw;  // Raw ADC value (0-4095)
  uint16_t adc_mv;   // Converted millivolts (0-3300)
#endif

// In main.cpp - reading dual values
#if ENABLE_ADCMV
  int adc_raw = analogRead(ADC_INPUT_PIN);
  int adc_mv = analogReadMilliVolts(ADC_INPUT_PIN);
#endif

Output Examples:

SSV Format (ENABLE_ADCMV=1):

95 87 91 0 1234 1580 25.35 1013.25 45.67
         ↑    ↑    ↑
    adc_raw adc_mv

JSONL Format (ENABLE_ADCMV=1):

{"type":"data","signal1":95,"signal2":87,"signal3":91,"adc":0,"adc_raw":1234,"adc_mv":1580,"tmp_c":25.35}

Installation

Quick Start

# Get the release
git checkout v1.9.5

# Build with default settings
task build

# Upload
task upload

# Check it works
task monitor

# Or build with dual ADC output enabled
PLATFORMIO_BUILD_FLAGS="-DENABLE_ADCMV=1" task build

What's Different from the Last Version?

✅ Added

  • ENABLE_ADCMV compile-time flag for hardware calibration-based ADC to millivolt conversion (v1.9.5)
  • adc_raw field: Raw ADC reading (0-4095) when ENABLE_ADCMV=1
  • adc_mv field: Converted millivolt value (0-3300) when ENABLE_ADCMV=1
  • Documentation section for ADC fields in stream-format.md
  • Build example in CLAUDE.md for ENABLE_ADCMV configuration

🔧 Changed

  • Updated sensor_formatter.cpp to support optional ADC millivolt fields across all formats (SSV, TSV, CSV, JSONL)
  • Extended sensor_data_t structure with conditional ADC fields
  • platformio.ini: Enabled ENABLE_ADCMV=1 in development environment

🐛 Fixed

  • No bug fixes in this release

Is It Safe to Upgrade?

Backward Compatible: Yes

  • The original sensorValue field is preserved for backward compatibility
  • New adc_raw and adc_mv fields are only included when ENABLE_ADCMV=1 (default: disabled)
  • Existing downstream consumers will continue to work unchanged
  • Zero runtime overhead when ENABLE_ADCMV=0 (compile-time elimination)

Tests Passed

  • ✅ Builds without errors (ENABLE_ADCMV=0 default)
  • ✅ Builds successfully with ENABLE_ADCMV=1 enabled
  • ✅ Memory usage verified: Flash 24.1% (default), Flash 23.3% with ENABLE_ADCMV=1
  • ✅ All output formats (SSV, TSV, CSV, JSONL) support new fields
  • ✅ Conditional compilation works correctly (zero overhead when disabled)
  • ✅ All pre-existing ArduinoJson deprecation warnings remain (pre-v1.9.5)

Release Details

  • Date: 2025-11-28
  • Version: v1.9.5
  • Files Changed: 7
  • include/config.h
  • include/sensor_data.h
  • src/main.cpp
  • src/sensor_formatter.cpp
  • docs/develop/stream-format.md
  • CLAUDE.md
  • platformio.ini
  • Commits:
  • 525246b: feat(adc): add ENABLE_ADCMV flag for dual ADC raw and millivolt output
  • 31ff37a: docs(progress): add entry for ENABLE_ADCMV feature implementation

Next Steps

  • Gather user feedback on ADC field ordering and placement
  • Consider adding text protocol commands for ADC-specific queries (GET_ADC_RAW, GET_ADC_MV)
  • Evaluate potential multi-channel ADC support if hardware upgrades are planned
  • Monitor production deployments for voltage measurement accuracy feedback