ESP32 读电池电量：为什么一条直线换算百分比不可靠？

// ---- BatteryVoltage.h ----
// SPDX-License-Identifier: MIT
#pragma once
#include <cmath>
struct Voltage {bool valid=false,dmmValid=false;double nominal=0,corrected=0;};
inline Voltage voltageEstimate(double raw,double adcMv,bool efuse,bool dmm,double gain,double offset){
 Voltage v;if(!efuse||!std::isfinite(raw)||!std::isfinite(adcMv)||raw<40||raw>4080||adcMv<1200||adcMv>2200)return v;
 v.nominal=adcMv*2.0;v.valid=true;
 if(dmm&&std::isfinite(gain)&&std::isfinite(offset)&&gain>=0.9&&gain<=1.1&&std::abs(offset)<=300){double x=gain*v.nominal+offset;if(x>=2400&&x<=4400){v.dmmValid=true;v.corrected=x;}}return v;
}

// ---- calibration.h ----
// SPDX-License-Identifier: MIT
#pragma once
// No site measurements exist. Keep disabled until YOUR board/meter/context has
// a reference dataset and independent check rows; tool output is not automatic proof.
constexpr bool DMM_CALIBRATED=false;
constexpr double DMM_GAIN=1.0;
constexpr double DMM_OFFSET_MV=0.0;

// ---- esp32-battery-voltage-monitor.ino ----
// SPDX-License-Identifier: MIT
#include <Arduino.h>
#include "esp_adc/adc_cali_scheme.h"
#include "BatteryVoltage.h"
#include "calibration.h"
static_assert(BATT_MONITOR==35,"Only Adafruit Feather ESP32 V2 GPIO35 divider is supported");
static bool factoryCalibration=false;
void setup(){
 Serial.begin(115200);
 pinMode(NEOPIXEL_I2C_POWER,OUTPUT);digitalWrite(NEOPIXEL_I2C_POWER,LOW); // core initVariant initially enabled this rail
 pinMode(LED_BUILTIN,OUTPUT);digitalWrite(LED_BUILTIN,LOW);
 analogReadResolution(12);analogSetPinAttenuation(BATT_MONITOR,ADC_11db);
 adc_cali_line_fitting_efuse_val_t efuse;esp_err_t e=adc_cali_scheme_line_fitting_check_efuse(&efuse);
 factoryCalibration=e==ESP_OK&&efuse!=ADC_CALI_LINE_FITTING_EFUSE_VAL_DEFAULT_VREF;
 delay(1500); // Rth~100k and C5=1uF => nominal tau~100ms; physical settling still must be checked
 Serial.printf("L07 Feather ESP32 V2 PID5400 RevF; ADC1 GPIO35; efuse_api=%s factory_cal=%u; no automatic battery/USB detection\n",esp_err_to_name(e),factoryCalibration);
 Serial.println("elapsed_ms,raw_mean,adc_mv,vbat_node_mv,dmm_corrected_mv,factory_cal,dmm_cal,status");
}
void loop(){
 // Raw and calibrated calls are separate conversions, not the same ADC sample.
 for(int i=0;i<4;i++){analogRead(BATT_MONITOR);delay(2);}
 uint32_t raw=0,mv=0;bool allConversions=true;for(int i=0;i<32;i++){uint16_t x=analogRead(BATT_MONITOR);raw+=x;if(x<40||x>4080)allConversions=false;if(factoryCalibration){uint32_t m=analogReadMilliVolts(BATT_MONITOR);mv+=m;if(!m)allConversions=false;}delay(2);}
 double a=raw/32.0,b=mv/32.0;Voltage v=voltageEstimate(allConversions?a:-1,b,factoryCalibration,DMM_CALIBRATED,DMM_GAIN,DMM_OFFSET_MV);
 Serial.printf("%lu,%.2f,",static_cast<unsigned long>(millis()),a);
 if(!factoryCalibration){Serial.println("NA,NA,NA,0,0,NO_EFUSE_CAL");}
 else if(!v.valid){Serial.printf("%.2f,NA,NA,1,0,RANGE_OR_ADC_ERROR\n",b);}
 else{Serial.printf("%.2f,%.2f,",b,v.nominal);if(v.dmmValid)Serial.printf("%.2f",v.corrected);else Serial.print("NA");Serial.printf(",1,%u,VBAT_NODE_ONLY\n",v.dmmValid);}
 delay(1000);
}