65 lines
1.9 KiB
C
65 lines
1.9 KiB
C
/*
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* Copyright (c) 2021 The ZMK Contributors
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*
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* SPDX-License-Identifier: MIT
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*/
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#include <errno.h>
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#include <zephyr/drivers/sensor.h>
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#include "battery_common.h"
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int battery_channel_get(const struct battery_value *value, enum sensor_channel chan,
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struct sensor_value *val_out) {
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switch (chan) {
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case SENSOR_CHAN_GAUGE_VOLTAGE:
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val_out->val1 = value->millivolts / 1000;
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val_out->val2 = (value->millivolts % 1000) * 1000U;
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break;
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case SENSOR_CHAN_GAUGE_STATE_OF_CHARGE:
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val_out->val1 = value->state_of_charge;
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val_out->val2 = 0;
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break;
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default:
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return -ENOTSUP;
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}
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return 0;
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}
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uint8_t lithium_ion_mv_to_pct(int16_t batt_mv) {
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// Lookup table of slope formulas for calculating remaining battery capacity.
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// The original values used to calculate slopes come from:
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//
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// https://blog.ampow.com/lipo-voltage-chart/
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//
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struct lookup_point {
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int16_t millivolts;
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int16_t percent;
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};
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static const struct lookup_point battery_lookup[] = {
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{.millivolts = 4200, .percent = 100}, {.millivolts = 3870, .percent = 60},
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{.millivolts = 3690, .percent = 10}, {.millivolts = 3610, .percent = 5},
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{.millivolts = 3270, .percent = 0},
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};
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if (batt_mv > battery_lookup[0].millivolts) {
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return battery_lookup[0].percent;
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}
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for (int i = 0; i < ARRAY_SIZE(battery_lookup); i++) {
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struct lookup_point one = battery_lookup[i - 1];
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struct lookup_point two = battery_lookup[i];
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if (batt_mv >= two.millivolts) {
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const int t = batt_mv - one.millivolts;
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const int dx = two.millivolts - one.millivolts;
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const int dy = two.percent - one.percent;
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return one.percent + dy * t / dx;
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}
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}
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return battery_lookup[ARRAY_SIZE(battery_lookup) - 1].percent;
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}
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