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/*
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* Copyright (c) 2020 The ZMK Contributors
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*
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* SPDX-License-Identifier: MIT
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*/
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#define DT_DRV_COMPAT zmk_battery_voltage_divider
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#include <device.h>
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#include <drivers/kscan.h>
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#include <drivers/gpio.h>
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#include <drivers/adc.h>
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#include <drivers/sensor.h>
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#include <logging/log.h>
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#include <math.h>
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LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
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#if DT_HAS_COMPAT_STATUS_OKAY(DT_DRV_COMPAT)
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#define VBATT DT_PATH(vbatt)
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struct battery_config {
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struct device *adc;
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struct adc_channel_cfg acc;
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struct adc_sequence as;
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int16_t adc_raw;
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};
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static struct battery_config battery_config;
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static int lithium_ion_mv_to_pct(int16_t bat_mv) {
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// Magic function that maps mV to this discharge graph from adafruit:
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// https://learn.adafruit.com/li-ion-and-lipoly-batteries/voltages
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return round(106.818 +
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(-0.032685 - 106.818) / pow(1 + pow(bat_mv / 3679.35, 58.979), 0.347386));
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}
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static void battery_read(struct k_work *workd) {
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struct battery_config *cfg = &battery_config;
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struct adc_sequence *as = &cfg->as;
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int rc = adc_read(cfg->adc, as);
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as->calibrate = false;
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if (rc == 0) {
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int32_t val = cfg->adc_raw;
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adc_raw_to_millivolts(adc_ref_internal(cfg->adc), cfg->acc.gain, as->resolution, &val);
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rc = val * (uint64_t)DT_PROP(VBATT, full_ohms) / DT_PROP(VBATT, output_ohms);
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LOG_DBG("ADC raw %d ~ %d mV => %d mV\n", cfg->adc_raw, val, rc);
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int percent = lithium_ion_mv_to_pct(rc);
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LOG_DBG("Percent: %d", percent);
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} else {
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LOG_DBG("Failed to read ADC: %d", rc);
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}
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}
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K_WORK_DEFINE(battery_work, battery_read);
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static void battery_handler(struct k_timer *timer) { k_work_submit(&battery_work); }
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K_TIMER_DEFINE(battery_tick, battery_handler, NULL);
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static int battery_setup(struct device *_arg) {
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struct battery_config *cfg = &battery_config;
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struct adc_sequence *as = &cfg->as;
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struct adc_channel_cfg *acc = &cfg->acc;
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cfg->adc = device_get_binding(DT_IO_CHANNELS_LABEL(VBATT));
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if (cfg->adc == NULL) {
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LOG_ERR("ADC %s failed to retrieve", DT_IO_CHANNELS_LABEL(VBATT));
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return -ENOENT;
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}
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*as = (struct adc_sequence){
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.channels = BIT(0),
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.buffer = &cfg->adc_raw,
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.buffer_size = sizeof(cfg->adc_raw),
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.oversampling = 4,
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.calibrate = true,
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};
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#ifdef CONFIG_ADC_NRFX_SAADC
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*acc = (struct adc_channel_cfg){
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.gain = ADC_GAIN_1_5,
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.reference = ADC_REF_INTERNAL,
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.acquisition_time = ADC_ACQ_TIME(ADC_ACQ_TIME_MICROSECONDS, 40),
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.input_positive = SAADC_CH_PSELP_PSELP_AnalogInput0 + DT_IO_CHANNELS_INPUT(VBATT),
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};
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as->resolution = 12;
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#else
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#error Unsupported ADC
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#endif
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int adc_rc = adc_channel_setup(cfg->adc, acc);
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LOG_DBG("AIN%u setup returned %d", DT_IO_CHANNELS_INPUT(VBATT), adc_rc);
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if (adc_rc != 0) {
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return adc_rc;
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}
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k_timer_start(&battery_tick, K_NO_WAIT, K_SECONDS(5));
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return 0;
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}
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SYS_INIT(battery_setup, APPLICATION, CONFIG_APPLICATION_INIT_PRIORITY);
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#endif /* DT_HAS_COMPAT_STATUS_OKAY(DT_DRV_COMPAT) */
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