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Fixes #1183 — T-Echo Lite incorrect battery voltage

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Battery (TechoBoard.h/cpp): Added PIN_VBAT_MEAS_EN (P0.31) — the T-Echo
Lite has a gated voltage divider that must be enabled before reading. Also
added pinMode(PIN_VBAT_READ, INPUT) before each ADC read to reclaim P0.02
from other peripherals. Pin definitions hardcoded from LilyGo's
t_echo_lite_config.h.

I2C (variant.h): Corrected SDA/SCL from P0.04/P0.02 to P1.04/P1.02 per
LilyGo's IIC_1_SDA/IIC_1_SCL. The old P0.02 mapping conflicted with the
battery ADC pin.

GPS (variant.h): Corrected all five GPS pin assignments to match LilyGo's
config — UART TX/RX, wake, PPS, and power enable were all scrambled.

SPI (variant.h): Fixed SPI_INTERFACES_COUNT from _PINNUM(0, 2) to (2).

Tested on T-Echo Lite Non-Shell (USB-C, no display). Battery readings match
Heltec V4 reference within 10mV.
This commit is contained in:
pelgraine
2026-04-10 14:25:51 +10:00
committed by Matthias Wientapper
parent 46b5076082
commit 8217a67f0c
3 changed files with 53 additions and 30 deletions
Download Patch File Download Diff File Expand all files Collapse all files

43
variants/lilygo_techo_lite/TechoBoard.cpp
View File

@@ -8,24 +8,47 @@
void TechoBoard::begin() {
NRF52Board::begin();
// Configure battery measurement control BEFORE Wire.begin()
// to ensure P0.02 is not claimed by another peripheral
pinMode(PIN_VBAT_MEAS_EN, OUTPUT);
digitalWrite(PIN_VBAT_MEAS_EN, LOW);
pinMode(PIN_VBAT_READ, INPUT);
Wire.begin();
pinMode(SX126X_POWER_EN, OUTPUT);
digitalWrite(SX126X_POWER_EN, HIGH);
delay(10); // give sx1262 some time to power up
delay(10);
}
uint16_t TechoBoard::getBattMilliVolts() {
int adcvalue = 0;
// Use LilyGo's exact ADC configuration
analogReference(AR_INTERNAL_3_0);
analogReadResolution(12);
delay(10);
// ADC range is 0..3000mV and resolution is 12-bit (0..4095)
adcvalue = analogRead(PIN_VBAT_READ);
// Convert the raw value to compensated mv, taking the resistor-
// divider into account (providing the actual LIPO voltage)
return (uint16_t)((float)adcvalue * REAL_VBAT_MV_PER_LSB);
// Enable battery voltage divider (MOSFET gate on P0.31)
pinMode(PIN_VBAT_MEAS_EN, OUTPUT);
digitalWrite(PIN_VBAT_MEAS_EN, HIGH);
// Reclaim P0.02 for analog input (in case another peripheral touched it)
pinMode(PIN_VBAT_READ, INPUT);
delay(10); // let divider + ADC settle
// Read and average (matching LilyGo's approach)
uint32_t sum = 0;
for (int i = 0; i < 8; i++) {
sum += analogRead(PIN_VBAT_READ);
delayMicroseconds(100);
}
uint16_t adc = sum / 8;
// Disable divider to save power
digitalWrite(PIN_VBAT_MEAS_EN, LOW);
// LilyGo's exact formula: adc * (3000.0 / 4096.0) * 2.0
// = adc * 0.73242188 * 2.0 = adc * 1.46484375
uint16_t millivolts = (uint16_t)((float)adc * (3000.0f / 4096.0f) * 2.0f);
return millivolts;
}
#endif
#endif