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.
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