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| 1 | +use crate::event::DeviceEvent; |
| 2 | +use esp_idf_svc::hal::adc::attenuation::DB_11; |
| 3 | +use esp_idf_svc::hal::adc::oneshot::config::{AdcChannelConfig, Calibration}; |
| 4 | +use esp_idf_svc::hal::adc::oneshot::{AdcChannelDriver, AdcDriver}; |
| 5 | +use esp_idf_svc::hal::adc::Resolution; |
| 6 | +use esp_idf_svc::hal::gpio::ADCPin; |
| 7 | +use esp_idf_svc::hal::peripheral::Peripheral; |
| 8 | +use log::info; |
| 9 | +use std::sync::mpsc; |
| 10 | +use std::thread; |
| 11 | +use std::thread::{Scope, ScopedJoinHandle}; |
| 12 | +use std::time::Duration; |
| 13 | + |
| 14 | +mod capacity_curve { |
| 15 | + use log::info; |
| 16 | + |
| 17 | + /// Naive const equivalent of `f.powi(n)`. |
| 18 | + /// Performance is not a problem, since this is evaluated only at compile time. |
| 19 | + /// Thanks to RFC 5314, basic floating point arithmetic is now stable in const |
| 20 | + const fn pow(f: f32, n: i32) -> f32 { |
| 21 | + let mut out: f32 = 1.0; |
| 22 | + let mut i = 0; |
| 23 | + while i < n { |
| 24 | + out *= f; |
| 25 | + i += 1; |
| 26 | + } |
| 27 | + out |
| 28 | + } |
| 29 | + |
| 30 | + /// Maps battery voltage (in mV) to battery capacity (in %). |
| 31 | + /// Calculated from battery datasheet using https://mycurvefit.com. |
| 32 | + const fn to_capacity(voltage: u16) -> u8 { |
| 33 | + const A: f32 = -0.22; |
| 34 | + // `B` is rounded from ~24.62 in order to use |
| 35 | + // deterministic version of `f32::powi` |
| 36 | + // (which is much easier to implement than `f32::powf`) |
| 37 | + const B: i32 = 25; // ~24.62; |
| 38 | + const C: f32 = 3662.97; |
| 39 | + const D: f32 = 104.42; |
| 40 | + |
| 41 | + let battery_level = (D + (A - D) / (1.0 + pow(voltage as f32 / C, B))) as i8; |
| 42 | + // `i8::clamp` as of March 2025 is not const |
| 43 | + if battery_level > 100 { |
| 44 | + return 100; |
| 45 | + } else if battery_level < 0 { |
| 46 | + return 0; |
| 47 | + } |
| 48 | + battery_level as u8 |
| 49 | + } |
| 50 | + |
| 51 | + /// `LOOKUP_RESOLUTION`mV per step |
| 52 | + const LOOKUP_RESOLUTION: u16 = 10; |
| 53 | + const LOOKUP_SIZE: usize = 121; |
| 54 | + const LOOKUP_START: u16 = 3000; |
| 55 | + const LOOKUP_END: u16 = LOOKUP_START + (LOOKUP_SIZE as u16 - 1) * LOOKUP_RESOLUTION; |
| 56 | + /// Maps voltage to capacity % |
| 57 | + /// Where `0` corresponds to `LOOKUP_START`mV |
| 58 | + /// and `LOOKUP_SIZE-1` corresponds to `LOOKUP_END`mV |
| 59 | + const CAPACITY_LOOKUP: [u8; LOOKUP_SIZE] = { |
| 60 | + let mut lookup: [u8; LOOKUP_SIZE] = [0; LOOKUP_SIZE]; |
| 61 | + // as of March 2025, for loops are not allowed in const context |
| 62 | + let mut i = 0; |
| 63 | + while i < LOOKUP_SIZE { |
| 64 | + lookup[i] = to_capacity(LOOKUP_START + i as u16 * LOOKUP_RESOLUTION); |
| 65 | + i += 1; |
| 66 | + } |
| 67 | + lookup |
| 68 | + }; |
| 69 | + |
| 70 | + /// Battery is connected to ADC pin through a voltage divider: |
| 71 | + /// `V_ADC = R7/(R6+R7) * V_BAT` |
| 72 | + /// `ADC_MULTIPLIER = (R6+R7)/R7` |
| 73 | + const ADC_MULTIPLIER: u8 = 2; |
| 74 | + #[inline] |
| 75 | + fn get_battery_voltage(adc_reading: u16) -> u16 { |
| 76 | + adc_reading * ADC_MULTIPLIER as u16 |
| 77 | + } |
| 78 | + |
| 79 | + /// If battery is charging, the ADC reading will show very high readings, above 4.2V. |
| 80 | + /// This would cause the battery level to always display 100%, when charging. |
| 81 | + /// There is no way to change this behaviour without hardware modifications. |
| 82 | + /// We can still naively check for unusually high voltage and assume that battery is charging. |
| 83 | + const CHARGING_THRESHOLD: u16 = 4300; |
| 84 | + |
| 85 | + /// Maps `adc_reading` to battery capacity (in %). |
| 86 | + /// Returns `None`, if battery is charging. |
| 87 | + #[inline] |
| 88 | + pub fn get_battery_level(adc_reading: u16) -> Option<u8> { |
| 89 | + let voltage = get_battery_voltage(adc_reading); |
| 90 | + info!("[Battery reader] Voltage: {:.2}V", voltage as f32 / 1000.0); |
| 91 | + if voltage > CHARGING_THRESHOLD { |
| 92 | + return None; |
| 93 | + } |
| 94 | + let lookup_index = |
| 95 | + ((voltage.clamp(LOOKUP_START, LOOKUP_END) - LOOKUP_START) / LOOKUP_RESOLUTION) as usize; |
| 96 | + Some(CAPACITY_LOOKUP[lookup_index]) |
| 97 | + } |
| 98 | +} |
| 99 | + |
| 100 | +pub fn spawn_reader_thread<'scope, T>( |
| 101 | + scope: &'scope Scope<'scope, '_>, |
| 102 | + adc: impl Peripheral<P = T::Adc> + 'scope + Send, |
| 103 | + battery_pin: impl Peripheral<P = T> + 'scope + Send, |
| 104 | + sender: mpsc::Sender<DeviceEvent>, |
| 105 | +) -> Result<ScopedJoinHandle<'scope, ()>, std::io::Error> |
| 106 | +where |
| 107 | + T: ADCPin, |
| 108 | +{ |
| 109 | + thread::Builder::new() |
| 110 | + .stack_size(8192) |
| 111 | + .spawn_scoped(scope, move || { |
| 112 | + info!("[Battery reader] Starting..."); |
| 113 | + let adc_driver = AdcDriver::new(adc).unwrap(); |
| 114 | + let mut bat_adc_channel = AdcChannelDriver::new( |
| 115 | + &adc_driver, |
| 116 | + battery_pin, |
| 117 | + &AdcChannelConfig { |
| 118 | + attenuation: DB_11, |
| 119 | + calibration: Calibration::Line, |
| 120 | + resolution: Resolution::Resolution12Bit, |
| 121 | + }, |
| 122 | + ) |
| 123 | + .unwrap(); |
| 124 | + loop { |
| 125 | + if let Ok(reading) = adc_driver.read(&mut bat_adc_channel) { |
| 126 | + let battery_level = capacity_curve::get_battery_level(reading); |
| 127 | + sender |
| 128 | + .send(DeviceEvent::BatteryLevel { |
| 129 | + data: battery_level, |
| 130 | + }) |
| 131 | + .ok(); |
| 132 | + match battery_level { |
| 133 | + Some(_) => { |
| 134 | + thread::sleep(Duration::from_secs(60)); |
| 135 | + } |
| 136 | + None => { |
| 137 | + thread::sleep(Duration::from_secs(2)); |
| 138 | + } |
| 139 | + } |
| 140 | + } |
| 141 | + } |
| 142 | + }) |
| 143 | +} |
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