Part 5: Battery

src/CMakeLists.txt

@@ -1,6 +1,7 @@
 idf_component_register(
 	SRCS
 	"main.c"
+	"odroid/battery.c"
 	"odroid/display.c"
 	"odroid/input.c"
 	"odroid/sdcard.c"

src/main.c

@@ -1,3 +1,4 @@
+#include "odroid/battery.h"
 #include "odroid/display.h"
 #include "odroid/input.h"
 #include "odroid/sdcard.h"
@@ -16,6 +17,7 @@ void app_main(void)
 	Odroid_InitializeInput();
 	Odroid_InitializeDisplay();
 	Odroid_InitializeSdcard();
+	Odroid_InitializeBatteryReader();
 
 	// Load sprite
 	uint16_t* sprite = (uint16_t*)malloc(64 * 64 * sizeof(uint16_t));
@@ -95,6 +97,20 @@ void app_main(void)
 			fclose(snapFile);
 		}
 
+
+		uint32_t batteryLevel = Odroid_ReadBatteryLevel();
+		ESP_LOGI(LOG_TAG, "Battery level: %u\n", batteryLevel);
+
+		if (batteryLevel < 3600)
+		{
+			Odroid_EnableBatteryLight();
+		}
+		else
+		{
+			Odroid_DisableBatteryLight();
+		}
+
+
 		Odroid_DrawFrame(gFramebuffer);
 	}
 

src/odroid/battery.c

@@ -0,0 +1,73 @@
+#include "battery.h"
+#include <driver/adc.h>
+#include <esp_adc_cal.h>
+#include <esp_log.h>
+#include <soc/adc_channel.h>
+
+
+static const char* LOG_TAG = "OdroidBattery";
+
+static const adc1_channel_t BATTERY_READ_PIN = ADC1_GPIO36_CHANNEL;
+static const gpio_num_t BATTERY_LED_PIN = GPIO_NUM_2;
+
+static esp_adc_cal_characteristics_t gCharacteristics;
+
+void Odroid_InitializeBatteryReader()
+{
+	// Configure LED
+	{
+		gpio_config_t gpioConfig = {};
+
+		gpioConfig.mode = GPIO_MODE_OUTPUT;
+		gpioConfig.pin_bit_mask = 1ULL << BATTERY_LED_PIN;
+
+		ESP_ERROR_CHECK(gpio_config(&gpioConfig));
+	}
+
+	// Configure ADC
+	{
+		adc1_config_width(ADC_WIDTH_BIT_12);
+		adc1_config_channel_atten(BATTERY_READ_PIN, ADC_ATTEN_DB_11);
+		adc1_config_channel_atten(BATTERY_READ_PIN, ADC_ATTEN_DB_11);
+
+		esp_adc_cal_value_t type = esp_adc_cal_characterize(
+			ADC_UNIT_1, ADC_ATTEN_DB_11, ADC_WIDTH_BIT_12, 1100, &gCharacteristics);
+
+		// The ESP32 in the Odroid Go should have its fuse set with a pre-calibrated vref
+		assert(type == ESP_ADC_CAL_VAL_EFUSE_VREF);
+	}
+
+	ESP_LOGI(LOG_TAG, "Battery reader initialized");
+}
+
+uint32_t Odroid_ReadBatteryLevel(void)
+{
+	const int SAMPLE_COUNT = 20;
+
+
+	uint32_t raw = 0;
+
+	for (int sampleIndex = 0; sampleIndex < SAMPLE_COUNT; ++sampleIndex)
+	{
+		raw += adc1_get_raw(BATTERY_READ_PIN);
+	}
+
+	raw /= SAMPLE_COUNT;
+
+
+	// Voltage divider reports half actual voltage
+	uint32_t voltage = 2 * esp_adc_cal_raw_to_voltage(raw, &gCharacteristics);
+
+	return voltage;
+}
+
+void Odroid_EnableBatteryLight(void)
+{
+	gpio_set_level(BATTERY_LED_PIN, 1);
+}
+
+void Odroid_DisableBatteryLight(void)
+{
+	gpio_set_level(BATTERY_LED_PIN, 0);
+}
+

src/odroid/battery.h

@@ -0,0 +1,10 @@
+#pragma once
+
+#include <stdint.h>
+
+
+void Odroid_InitializeBatteryReader(void);
+uint32_t Odroid_ReadBatteryLevel(void);
+void Odroid_EnableBatteryLight(void);
+void Odroid_DisableBatteryLight(void);
+