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HeltecV4: Fix battery ADC reading accuracy #2689

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HeltecV4: Fix battery ADC reading accuracy #2689

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7dd5c7a
HeltecV4: Fix battery ADC reading accuracy
TPRoberts Jun 5, 2026
b32182e
HeltecV4: Use ADC_2_5db attenuation for battery reading
TPRoberts Jun 5, 2026
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11 changes: 6 additions & 5 deletions variants/heltec_v4/HeltecV4Board.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -62,18 +62,19 @@ void HeltecV4Board::begin() {
}

uint16_t HeltecV4Board::getBattMilliVolts() {
analogReadResolution(10);
analogReadResolution(12);
analogSetPinAttenuation(PIN_VBAT_READ, ADC_2_5db); // divider puts pin at 0.61-0.86V; 2.5dB gives headroom over ADC_0db for chip variation
digitalWrite(PIN_ADC_CTRL, HIGH);
delay(10);
uint32_t raw = 0;
uint32_t raw_mv = 0;
for (int i = 0; i < 8; i++) {
raw += analogRead(PIN_VBAT_READ);
raw_mv += analogReadMilliVolts(PIN_VBAT_READ);
}
raw = raw / 8;
raw_mv /= 8;

digitalWrite(PIN_ADC_CTRL, LOW);

return (adc_mult * (3.3 / 1024.0) * raw) * 1000;
return adc_mult * raw_mv;
}

const char* HeltecV4Board::getManufacturerName() const {
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2 changes: 1 addition & 1 deletion variants/heltec_v4/HeltecV4Board.h
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Expand Up @@ -7,7 +7,7 @@
#include "LoRaFEMControl.h"

#ifndef ADC_MULTIPLIER
#define ADC_MULTIPLIER 5.42
#define ADC_MULTIPLIER 4.9 // (R1+R2)/R2 = (390k+100k)/100k
#endif

class HeltecV4Board : public ESP32Board {
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