Move battery measurement to its own class

1 files changed, 67 insertions, 0 deletions

diff --git a/src/drivers/adc.cpp b/src/drivers/adc.cpp
new file mode 100644
index 00000000..56d2cbb4
--- /dev/null
+++ b/src/drivers/adc.cpp
@@ -0,0 +1,67 @@
+/*
+ * Copyright 2023 jacqueline <me@jacqueline.id.au>
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include "adc.hpp"
+#include <cstdint>
+
+#include "esp_adc/adc_cali.h"
+#include "esp_adc/adc_cali_scheme.h"
+#include "esp_adc/adc_oneshot.h"
+#include "hal/adc_types.h"
+
+namespace drivers {
+
+static const adc_bitwidth_t kAdcBitWidth = ADC_BITWIDTH_12;
+static const adc_unit_t kAdcUnit = ADC_UNIT_1;
+// Max battery voltage should be a little over 2V due to our divider, so we need
+// the max attenuation to properly handle the full range.
+static const adc_atten_t kAdcAttenuation = ADC_ATTEN_DB_11;
+// Corresponds to SENSOR_VP.
+static const adc_channel_t kAdcChannel = ADC_CHANNEL_0;
+
+AdcBattery::AdcBattery() {
+  adc_oneshot_unit_init_cfg_t unit_config = {
+      .unit_id = kAdcUnit,
+  };
+  ESP_ERROR_CHECK(adc_oneshot_new_unit(&unit_config, &adc_handle_));
+
+  adc_oneshot_chan_cfg_t channel_config = {
+      .atten = kAdcAttenuation,
+      .bitwidth = kAdcBitWidth,
+  };
+  ESP_ERROR_CHECK(
+      adc_oneshot_config_channel(adc_handle_, kAdcChannel, &channel_config));
+
+  // calibrate
+  // TODO: compile-time assert our scheme is available
+  adc_cali_line_fitting_config_t calibration_config = {
+      .unit_id = kAdcUnit,
+      .atten = kAdcAttenuation,
+      .bitwidth = kAdcBitWidth,
+  };
+  ESP_ERROR_CHECK(adc_cali_create_scheme_line_fitting(
+      &calibration_config, &adc_calibration_handle_));
+}
+
+AdcBattery::~AdcBattery() {
+  adc_cali_delete_scheme_line_fitting(adc_calibration_handle_);
+  ESP_ERROR_CHECK(adc_oneshot_del_unit(adc_handle_));
+}
+
+auto AdcBattery::Millivolts() -> uint32_t {
+  // GPIO 34
+  int raw = 0;
+  ESP_ERROR_CHECK(adc_oneshot_read(adc_handle_, kAdcChannel, &raw));
+
+  int voltage = 0;
+  ESP_ERROR_CHECK(
+      adc_cali_raw_to_voltage(adc_calibration_handle_, raw, &voltage));
+
+  // Voltage divider halves the battery voltage to get it into the ADC's range.
+  return voltage * 2;
+}
+
+}  // namespace drivers