factor out adc battery measurement

idk if this should be classy or if this is fine. maybe should just pick
a convention at some point?

1 files changed, 31 insertions, 0 deletions

diff --git a/main/battery.cpp b/main/battery.cpp
new file mode 100644
index 00000000..ef23bfc0
--- /dev/null
+++ b/main/battery.cpp
@@ -0,0 +1,31 @@
+#include "battery.c"
+
+#include "driver/adc.h"
+#include "esp_adc_cal.h"
+#include "hal/adc_types.h"
+
+namespace gay_ipod {
+
+static esp_adc_cal_characteristics_t calibration;
+
+esp_error_t init_adc(void) {
+  // Calibration should already be fused into the chip from the factory, so
+  // we should only need to read it back out again.
+  esp_adc_cal_characterize(
+      ADC_UNIT_1, ADC_ATTEN_DB_11, ADC_WIDTH_BIT_12, 0, &calibration);
+
+  // 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.
+  adc1_config_width(ADC_WIDTH_BIT_12);
+  adc1_config_channel_atten(ADC1_CHANNEL_6, ADC_ATTEN_DB_11);
+
+  return ESP_OK;
+}
+
+uint32_t read_battery_voltage(void) {
+  // GPIO 34
+  int raw = adc1_get_raw(ADC1_CHANNEL_6);
+  return esp_adc_cal_raw_to_voltage(raw, &calibration);
+}
+
+} // namespace gay_ipod