README.md

Read Battery Voltage

This program lets you read the Battery voltage from the Glyph C3

To allow this first short the MSR pads at the bottom.

Circuit

Code

use esp_idf_svc::hal::prelude::*;
use esp_idf_svc::hal::adc::oneshot::{AdcDriver, AdcChannelDriver, config::AdcChannelConfig};
use esp_idf_svc::hal::adc::attenuation::DB_11;
use esp_idf_svc::hal::adc::ADC1;
use esp_idf_svc::hal::gpio::{Gpio0, PinDriver}; // Added PinDriver
use std::thread;
use std::time::Duration;

pub struct BatteryMonitor<'a> {
    adc: &'a AdcDriver<'a, ADC1>,
    pin: AdcChannelDriver<'a, Gpio0, &'a AdcDriver<'a, ADC1>>,
}

impl<'a> BatteryMonitor<'a> {
    pub fn new(
        adc: &'a AdcDriver<'a, ADC1>, 
        pin: AdcChannelDriver<'a, Gpio0, &'a AdcDriver<'a, ADC1>>
    ) -> Self {
        Self { adc, pin }
    }

    // Returns (Percentage, Voltage, Raw_ADC_Value)
    pub fn get_status(&mut self) -> (u8, f32, u16) {
        let raw_value = self.adc.read(&mut self.pin).unwrap_or(0);

        // 1. Convert Raw to Voltage at Pin (0-2.5V range)
        let voltage_pin = (raw_value as f32 / 4095.0) * 2.5; 
        
        // 2. Convert to Battery Voltage
        // HYPOTHESIS: The divider is 1/4 (e.g. 300k/100k)
        let voltage_bat = voltage_pin * 4.0;

        let percentage = if voltage_bat >= 4.2 {
            100
        } else if voltage_bat <= 3.0 {
            0
        } else {
            ((voltage_bat - 3.0) / (4.2 - 3.0) * 100.0) as u8
        };

        (percentage, voltage_bat, raw_value)
    }
}

fn main() -> anyhow::Result<()> {
    esp_idf_svc::sys::link_patches();
    esp_idf_svc::log::EspLogger::initialize_default();

    let peripherals = Peripherals::take()?;

    log::info!("Starting Battery Monitor with LED...");

    let adc = AdcDriver::new(peripherals.adc1)?;

    let config = AdcChannelConfig {
        attenuation: DB_11,
        ..Default::default()
    };

    let adc_pin = AdcChannelDriver::new(&adc, peripherals.pins.gpio0, &config)?;
    let mut monitor = BatteryMonitor::new(&adc, adc_pin);

    // --- LED SETUP ---
    // GPIO 8 is standard for Onboard LED on C3 SuperMini/Glyph
    let mut led = PinDriver::output(peripherals.pins.gpio1)?;

    loop {
        let (pct, volts, raw) = monitor.get_status();
        log::info!("Bat: {}% | Volts: {:.2}V | Raw: {}", pct, volts, raw);
        
        // --- LED LOGIC ---
        // Note: Onboard LEDs are usually "Active Low" (0 = ON, 1 = OFF)
        if pct > 70 {
            // High Battery -> Solid ON
            led.set_high()?; 
        } else if pct < 50 {
            // Low Battery -> Blink
            led.toggle()?;
        } else {
            // Medium Battery (50-70%) -> OFF
            led.set_low()?;
        }
        
        // Loop every 500ms for a nice blinking speed
        thread::sleep(Duration::from_millis(500));
    }
}