From e525a823dc70f9421a78782c4dc1ae0ffad75be4 Mon Sep 17 00:00:00 2001
From: Austin Morlan <mail@austinmorlan.com>
Date: Thu, 21 May 2020 21:44:29 -0700
Subject: [PATCH] Part 5: Battery

---
 src/CMakeLists.txt   |  1 +
 src/main.c           | 16 ++++++++++
 src/odroid/battery.c | 73 ++++++++++++++++++++++++++++++++++++++++++++
 src/odroid/battery.h | 10 ++++++
 4 files changed, 100 insertions(+)
 create mode 100644 src/odroid/battery.c
 create mode 100644 src/odroid/battery.h

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 80e9f56..53ac103 100644
--- a/src/CMakeLists.txt
+++ b/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"
diff --git a/src/main.c b/src/main.c
index 6fc69c8..1b8e607 100644
--- a/src/main.c
+++ b/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);
 	}
 
diff --git a/src/odroid/battery.c b/src/odroid/battery.c
new file mode 100644
index 0000000..b06f23b
--- /dev/null
+++ b/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);
+}
+
diff --git a/src/odroid/battery.h b/src/odroid/battery.h
new file mode 100644
index 0000000..607fe46
--- /dev/null
+++ b/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);
+