feat: Add nrf VDDH battery driver

Added a driver which uses the nRF52's ADC channel on the VDDH pin to
read the battery voltage when using high voltage mode.

1 files changed, 116 insertions, 0 deletions

diff --git a/app/drivers/sensor/battery/battery_nrf_vddh.c b/app/drivers/sensor/battery/battery_nrf_vddh.c
new file mode 100644
index 0000000..9089034
--- /dev/null
+++ b/app/drivers/sensor/battery/battery_nrf_vddh.c
@@ -0,0 +1,116 @@
+/*
+ * Copyright (c) 2021 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * This is a simplified version of battery_voltage_divider.c which always reads
+ * the VDDHDIV5 channel of the &adc node and multiplies it by 5.
+ */
+
+#define DT_DRV_COMPAT zmk_battery_nrf_vddh
+
+#include <device.h>
+#include <devicetree.h>
+#include <drivers/adc.h>
+#include <drivers/sensor.h>
+#include <logging/log.h>
+
+#include "battery_common.h"
+
+LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
+
+#define VDDHDIV (5)
+
+static const struct device *adc = DEVICE_DT_GET(DT_NODELABEL(adc));
+
+struct vddh_data {
+    struct adc_channel_cfg acc;
+    struct adc_sequence as;
+    struct battery_value value;
+};
+
+static int vddh_sample_fetch(const struct device *dev, enum sensor_channel chan) {
+    // Make sure selected channel is supported
+    if (chan != SENSOR_CHAN_GAUGE_VOLTAGE && chan != SENSOR_CHAN_GAUGE_STATE_OF_CHARGE &&
+        chan != SENSOR_CHAN_ALL) {
+        LOG_DBG("Selected channel is not supported: %d.", chan);
+        return -ENOTSUP;
+    }
+
+    struct vddh_data *drv_data = dev->data;
+    struct adc_sequence *as = &drv_data->as;
+
+    int rc = adc_read(adc, as);
+    as->calibrate = false;
+
+    if (rc != 0) {
+        LOG_ERR("Failed to read ADC: %d", rc);
+        return rc;
+    }
+
+    int32_t val = drv_data->value.adc_raw;
+    rc = adc_raw_to_millivolts(adc_ref_internal(adc), drv_data->acc.gain, as->resolution, &val);
+    if (rc != 0) {
+        LOG_ERR("Failed to convert raw ADC to mV: %d", rc);
+        return rc;
+    }
+
+    drv_data->value.millivolts = val * VDDHDIV;
+    drv_data->value.state_of_charge = lithium_ion_mv_to_pct(drv_data->value.millivolts);
+
+    LOG_DBG("ADC raw %d ~ %d mV => %d%%", drv_data->value.adc_raw, drv_data->value.millivolts,
+            drv_data->value.state_of_charge);
+
+    return rc;
+}
+
+static int vddh_channel_get(const struct device *dev, enum sensor_channel chan,
+                            struct sensor_value *val) {
+    struct vddh_data const *drv_data = dev->data;
+    return battery_channel_get(&drv_data->value, chan, val);
+}
+
+static const struct sensor_driver_api vddh_api = {
+    .sample_fetch = vddh_sample_fetch,
+    .channel_get = vddh_channel_get,
+};
+
+static int vddh_init(const struct device *dev) {
+    struct vddh_data *drv_data = dev->data;
+
+    if (!device_is_ready(adc)) {
+        LOG_ERR("ADC device is not ready %s", adc->name);
+        return -ENODEV;
+    }
+
+    drv_data->as = (struct adc_sequence){
+        .channels = BIT(0),
+        .buffer = &drv_data->value.adc_raw,
+        .buffer_size = sizeof(drv_data->value.adc_raw),
+        .oversampling = 4,
+        .calibrate = true,
+    };
+
+#ifdef CONFIG_ADC_NRFX_SAADC
+    drv_data->acc = (struct adc_channel_cfg){
+        .gain = ADC_GAIN_1_5,
+        .reference = ADC_REF_INTERNAL,
+        .acquisition_time = ADC_ACQ_TIME(ADC_ACQ_TIME_MICROSECONDS, 40),
+        .input_positive = SAADC_CH_PSELN_PSELN_VDDHDIV5,
+    };
+
+    drv_data->as.resolution = 12;
+#else
+#error Unsupported ADC
+#endif
+
+    const int rc = adc_channel_setup(adc, &drv_data->acc);
+    LOG_DBG("VDDHDIV5 setup returned %d", rc);
+
+    return rc;
+}
+
+static struct vddh_data vddh_data;
+
+DEVICE_DT_INST_DEFINE(0, &vddh_init, device_pm_control_nop, &vddh_data, NULL, POST_KERNEL,
+                      CONFIG_SENSOR_INIT_PRIORITY, &vddh_api);