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/*
* Copyright 2023 jacqueline <me@jacqueline.id.au>
*
* SPDX-License-Identifier: GPL-3.0-only
*/
#include "battery/battery.hpp"
#include <stdint.h>
#include <cmath>
#include <cstdint>
#include "drivers/adc.hpp"
#include "drivers/samd.hpp"
#include "events/event_queue.hpp"
#include "freertos/portmacro.h"
#include "system_fsm/system_events.hpp"
namespace battery {
static const TickType_t kBatteryCheckPeriod = pdMS_TO_TICKS(60 * 1000);
/*
* Battery voltage, in millivolts, at which the battery charger IC will stop
* charging.
*/
static const uint32_t kFullChargeMilliVolts = 4200;
static const uint32_t kCriticalChargeMilliVolts = 3500;
/*
* Battery voltage, in millivolts, at which *we* will consider the battery to
* be completely discharged. This is intentionally higher than the charger IC
* cut-off and the protection on the battery itself; we want to make sure we
* finish up and have everything unmounted and snoozing before the BMS cuts us
* off.
*/
static const uint32_t kEmptyChargeMilliVolts = 3200; // BMS limit is 3100.
using ChargeStatus = drivers::Samd::ChargeStatus;
static void check_voltage_cb(TimerHandle_t timer) {
Battery* instance = reinterpret_cast<Battery*>(pvTimerGetTimerID(timer));
instance->Update();
}
Battery::Battery(drivers::Samd& samd, std::unique_ptr<drivers::AdcBattery> adc)
: samd_(samd), adc_(std::move(adc)) {
timer_ = xTimerCreate("BATTERY", kBatteryCheckPeriod, true, this,
check_voltage_cb);
xTimerStart(timer_, portMAX_DELAY);
Update();
}
Battery::~Battery() {
xTimerStop(timer_, portMAX_DELAY);
xTimerDelete(timer_, portMAX_DELAY);
}
auto Battery::Update() -> void {
std::lock_guard<std::mutex> lock{state_mutex_};
auto charge_state = samd_.GetChargeStatus();
uint32_t mV = std::max(adc_->Millivolts(), kEmptyChargeMilliVolts);
// Ideally the way you're 'supposed' to measure battery charge percent is to
// keep continuous track of the amps going in and out of it at any point. I'm
// skeptical of this approach, and we're not set up with the hardware needed
// to do it anyway. Instead, we use a piecewise linear formula derived from
// voltage measurements of our actual cells.
uint_fast8_t percent;
if (mV > kCriticalChargeMilliVolts) {
// Above the 'critical' point, the relationship between battery voltage and
// charge percentage is close enough to linear.
percent = ((mV - kCriticalChargeMilliVolts) * 100 /
(kFullChargeMilliVolts - kCriticalChargeMilliVolts)) +
5;
} else {
// Below the 'critical' point, battery voltage drops very very quickly.
// Give this part of the curve the lowest 5% to work with.
percent = (mV - kEmptyChargeMilliVolts) * 5 /
(kCriticalChargeMilliVolts - kEmptyChargeMilliVolts);
}
// A full charge is always 100%.
if (charge_state == ChargeStatus::kFullCharge) {
percent = 100;
}
// Critical charge is always <= 5%
if (charge_state == ChargeStatus::kBatteryCritical) {
percent = std::min<uint_fast8_t>(percent, 5);
}
// When very close to full, the BMS transitions to a constant-voltage charge
// algorithm. Hold off on reporting 100% charge until this stage is finished.
if (percent >= 95 && charge_state != ChargeStatus::kFullCharge) {
percent = std::min<uint_fast8_t>(percent, 95);
}
bool is_charging;
if (!charge_state) {
is_charging = false;
} else {
is_charging = *charge_state == ChargeStatus::kChargingRegular ||
*charge_state == ChargeStatus::kChargingFast ||
*charge_state == ChargeStatus::kFullCharge ||
// Treat 'no battery' as charging because, for UI purposes,
// we're *kind of* at full charge if u think about it.
*charge_state == ChargeStatus::kNoBattery;
}
if (state_ && state_->is_charging == is_charging &&
state_->percent == percent) {
return;
}
state_ = BatteryState{
.percent = percent,
.millivolts = mV,
.is_charging = is_charging,
.raw_status =
charge_state.value_or(drivers::Samd::ChargeStatus::kUnknown),
};
EmitEvent();
}
auto Battery::State() -> std::optional<BatteryState> {
std::lock_guard<std::mutex> lock{state_mutex_};
return state_;
}
auto Battery::EmitEvent() -> void {
auto state = state_;
if (!state) {
return;
}
system_fsm::BatteryStateChanged ev{
.new_state = *state,
};
events::System().Dispatch(ev);
events::Ui().Dispatch(ev);
}
} // namespace battery
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