diff --git a/main/CMakeLists.txt b/main/CMakeLists.txt
index 30cf37b..4544650 100644
--- a/main/CMakeLists.txt
+++ b/main/CMakeLists.txt
@@ -2,6 +2,7 @@ idf_component_register(SRCS
     "main.c"
     "app_task_led.c"
     "app_task_epd.c"
+    "app_task_battery.c"
     "app_lib_i2c_system.c"
     "app_lib_bat_impl.c"
     "app_lib_epd_impl.c"
diff --git a/main/app_lib_bat_impl.c b/main/app_lib_bat_impl.c
index ac6b40f..b9bdbe1 100644
--- a/main/app_lib_bat_impl.c
+++ b/main/app_lib_bat_impl.c
@@ -1,15 +1,52 @@
 #include "esp_log.h"
-#include "driver/i2c.h"
+
+#include "user_board.h"
 
 #include "app_lib_bat_impl.h"
 
 #define LTC2941_ADDR 0x64 // Unshifted
 
-static const char *TAG = "BAT_IMPL"
+static const char *TAG = "BAT_IMPL";
 
 ltc2941_ret_t app_lib_bat_read_register(app_lib_bat_impl_t *impl, uint8_t reg, uint8_t *value) {
+    ESP_LOGD(TAG, "Read register: %d", reg);
 
+    i2c_cmd_handle_t cmd = i2c_cmd_link_create();
+    i2c_master_start(cmd);
+    i2c_master_write_byte(cmd, LTC2941_ADDR << 1 | I2C_MASTER_WRITE, true);
+    i2c_master_write_byte(cmd, reg, true);
+    i2c_master_start(cmd);
+    i2c_master_write_byte(cmd, LTC2941_ADDR << 1 | I2C_MASTER_READ, true);
+    i2c_master_read_byte(cmd, value, I2C_MASTER_LAST_NACK);
+    i2c_master_stop(cmd);
+
+    esp_err_t err = i2c_master_cmd_begin(impl->i2c_num, cmd, pdMS_TO_TICKS(1000));
+    i2c_cmd_link_delete(cmd);
+
+    if(err != ESP_OK) {
+        ESP_LOGE(TAG, "Read register reported error, %s", esp_err_to_name(err));
+        return LTC2941_ERROR;
+    }
+
+    return LTC2941_OK;
 }
 ltc2941_ret_t app_lib_bat_write_register(app_lib_bat_impl_t *impl, uint8_t reg, uint8_t value) {
+    ESP_LOGD(TAG, "Write register: %d", reg);
 
+    i2c_cmd_handle_t cmd = i2c_cmd_link_create();
+    i2c_master_start(cmd);
+    i2c_master_write_byte(cmd, LTC2941_ADDR << 1 | I2C_MASTER_WRITE, true);
+    i2c_master_write_byte(cmd, reg, true);
+    i2c_master_write_byte(cmd, value, true);
+    i2c_master_stop(cmd);
+
+    esp_err_t err = i2c_master_cmd_begin(impl->i2c_num, cmd, pdMS_TO_TICKS(1000));
+    i2c_cmd_link_delete(cmd);
+
+    if(err != ESP_OK) {
+        ESP_LOGE(TAG, "Write register reported error, %s", esp_err_to_name(err));
+        return LTC2941_ERROR;
+    }
+
+    return LTC2941_OK;
 }
\ No newline at end of file
diff --git a/main/app_lib_bat_impl.h b/main/app_lib_bat_impl.h
index 56969ac..81bd510 100644
--- a/main/app_lib_bat_impl.h
+++ b/main/app_lib_bat_impl.h
@@ -1,10 +1,12 @@
 #ifndef __APP_LIB_BAT_IMPL_H
 #define __APP_LIB_BAT_IMPL_H
 
+#include "driver/i2c.h"
+
 #include "ltc2941_battery.h"
 
 typedef struct {
-
+    int i2c_num;
 } app_lib_bat_impl_t;
 
 ltc2941_ret_t app_lib_bat_read_register(app_lib_bat_impl_t *impl, uint8_t reg, uint8_t *value);
diff --git a/main/app_lib_epd_impl.c b/main/app_lib_epd_impl.c
index e69de29..e902a6f 100644
--- a/main/app_lib_epd_impl.c
+++ b/main/app_lib_epd_impl.c
@@ -0,0 +1,114 @@
+#include "freertos/FreeRTOS.h"
+#include "freertos/task.h"
+
+#include "user_board.h"
+
+#include "app_lib_epd_impl.h"
+
+#define MAXIMUM_XFER_SIZE 400 * 300 / 8 // FULL fb.
+#define MAX_BUSY_POLL_COUNT 10
+
+static void _spi_pre_transfere_callback(spi_transaction_t *txn) {
+    gpio_set_level(BOARD_EPD_DC_PIN, (int)txn->user);
+}
+
+void app_lib_epd_impl_init(app_lib_epd_impl_t *impl) {
+    gpio_config_t io_config = {
+        .intr_type = GPIO_INTR_DISABLE,
+        .mode = GPIO_MODE_OUTPUT_OD,
+        .pin_bit_mask = (1 << BOARD_EPD_RES_PIN),
+        .pull_up_en = GPIO_PULLUP_ENABLE,
+        .pull_down_en = GPIO_PULLDOWN_DISABLE
+    };
+    gpio_config(&io_config);
+
+    io_config.pin_bit_mask = (1 << BOARD_EPD_DC_PIN);
+    io_config.pull_up_en = GPIO_PULLUP_DISABLE;
+    io_config.mode = GPIO_MODE_OUTPUT;
+    gpio_config(&io_config);
+
+    io_config.pin_bit_mask = (1 << BOARD_EPD_BUSY_PIN);
+    io_config.mode = GPIO_MODE_INPUT;
+    gpio_config(&io_config);
+
+    spi_bus_config_t bus_cfg = {
+        .mosi_io_num = BOARD_EPD_SPI_MOSI_PIN,
+        .sclk_io_num = BOARD_EPD_SPI_SCK_PIN,
+        .miso_io_num = -1,
+        .quadhd_io_num = -1,
+        .quadwp_io_num = -1,
+        .max_transfer_sz = MAXIMUM_XFER_SIZE
+    };
+
+    spi_device_interface_config_t interface_config = {
+        .clock_speed_hz = 8 * 1000 * 1000,
+        .mode = 0,
+        .spics_io_num = BOARD_EPD_SPI_CS_PIN,
+        .queue_size = 7,
+        .pre_cb = _spi_pre_transfere_callback,
+    };
+
+    ESP_ERROR_CHECK(spi_bus_initialize(SPI2_HOST, &bus_cfg, SPI_DMA_CH_AUTO));
+    ESP_ERROR_CHECK(spi_bus_add_device(SPI2_HOST, &interface_config, &impl->spi_handle));
+}
+
+gd_epd_042_ret_t app_lib_epd_impl_reset(app_lib_epd_impl_t *impl) {
+    gpio_set_level(BOARD_EPD_RES_PIN, 1);
+    vTaskDelay(10);
+    gpio_set_level(BOARD_EPD_RES_PIN, 0);
+    vTaskDelay(10);
+    gpio_set_level(BOARD_EPD_RES_PIN, 1);
+    vTaskDelay(10);
+
+    return EPD_OK;
+}
+
+gd_epd_042_ret_t app_lib_epd_impl_write_cmd(app_lib_epd_impl_t *impl, uint8_t *cmd, uint8_t len) {
+    esp_err_t ret;
+    spi_transaction_t txn = {
+        .length = 8,
+        .tx_buffer = cmd,
+        .user = (void *)0
+    };
+
+    ret = spi_device_polling_transmit(impl->spi_handle, &txn);
+    if(ret != ESP_OK) return EPD_ERR;
+
+    if(len > 1) {
+        txn.length = 8 * len - 1;
+        txn.tx_buffer = &cmd[1];
+
+        ret = spi_device_polling_transmit(impl->spi_handle, &txn);
+        if(ret != ESP_OK) return EPD_ERR;
+    }
+
+    return EPD_OK;
+}
+
+gd_epd_042_ret_t app_lib_epd_impl_write_data(app_lib_epd_impl_t *impl, uint8_t *data, uint32_t len) {
+    esp_err_t ret;
+    spi_transaction_t txn = {
+        .length = 8 * len,
+        .tx_buffer = data,
+        .user = (void *)1
+    };
+
+    ret = spi_device_polling_transmit(impl->spi_handle, &txn);
+
+    if(ret != ESP_OK) return EPD_ERR;
+    return EPD_OK;
+}
+
+gd_epd_042_ret_t app_lib_epd_impl_poll_busy(app_lib_epd_impl_t *impl) {
+    uint8_t count = MAX_BUSY_POLL_COUNT;
+    while(gpio_get_level(BOARD_EPD_BUSY_PIN) == 0) {
+        vTaskDelay(10);
+        if(count == 0) {
+            return EPD_ERR;
+        }
+        count--;
+    }
+
+    return EPD_OK;
+
+}
\ No newline at end of file
diff --git a/main/app_lib_epd_impl.h b/main/app_lib_epd_impl.h
index f7e4076..03fce9c 100644
--- a/main/app_lib_epd_impl.h
+++ b/main/app_lib_epd_impl.h
@@ -1,6 +1,19 @@
 #ifndef __APP_LIB_EPD_IMPL_H
 #define __APP_LIB_EPD_IMPL_H
 
+#include "driver/spi_master.h"
+#include "driver/gpio.h"
 
+#include "gdew042t2_epd.h"
+
+typedef struct {
+    spi_device_handle_t spi_handle;
+} app_lib_epd_impl_t;
+
+void app_lib_epd_impl_init(app_lib_epd_impl_t *impl);
+gd_epd_042_ret_t app_lib_epd_impl_reset(app_lib_epd_impl_t *impl);
+gd_epd_042_ret_t app_lib_epd_impl_write_cmd(app_lib_epd_impl_t *impl, uint8_t *cmd, uint8_t len);
+gd_epd_042_ret_t app_lib_epd_impl_write_data(app_lib_epd_impl_t *impl, uint8_t *data, uint32_t len);
+gd_epd_042_ret_t app_lib_epd_impl_poll_busy(app_lib_epd_impl_t *impl);
 
 #endif
\ No newline at end of file
diff --git a/main/app_lib_i2c_system.c b/main/app_lib_i2c_system.c
index 8ad08ee..a377e4a 100644
--- a/main/app_lib_i2c_system.c
+++ b/main/app_lib_i2c_system.c
@@ -8,9 +8,9 @@ void app_lib_i2c_system_init(void) {
         .mode = I2C_MODE_MASTER,
         .sda_io_num = BOARD_SYSTEM_I2C_SDA_PIN,
         .scl_io_num = BOARD_SYSTEM_I2C_SCL_PIN,
-        .sda_pullup_en = GPIO_PULLUP_DISABLE,
-        .scl_pullup_en = GPIO_PULLUP_DISABLE,
-        .master.clk_speed = 400000
+        .sda_pullup_en = GPIO_PULLUP_ENABLE,
+        .scl_pullup_en = GPIO_PULLUP_ENABLE,
+        .master.clk_speed = 100000
     };
 
     esp_err_t err = i2c_param_config(BOARD_SYSTEM_I2C_NUM, &conf);
diff --git a/main/app_task_battery.c b/main/app_task_battery.c
new file mode 100644
index 0000000..96317b6
--- /dev/null
+++ b/main/app_task_battery.c
@@ -0,0 +1,48 @@
+#include "freertos/FreeRTOS.h"
+#include "freertos/task.h"
+#include "freertos/queue.h"
+
+#include "esp_log.h"
+
+#include "user_board.h"
+
+#include "app_lib_bat_impl.h"
+
+#define BATTERY_CAP 3000.0
+#define MAH_LSB 0.053125 // Shunt 20mR
+#define PRESCALER_M LTC2941_PRE_32
+
+const static char *TAG = "TASK_BAT";
+
+TaskHandle_t xTaskBatteryExampleHandle = NULL;
+void vTasBatteryExample(void *pvParameters) {
+    app_lib_bat_impl_t impl = {
+        .i2c_num = BOARD_SYSTEM_I2C_NUM
+    };
+
+    ltc2941_t battery_fg = {
+        .user_data = &impl,
+        .cb = {
+            .read_register_cb = (ltc2941_ret_t (*)(void *, uint8_t, uint8_t *))app_lib_bat_read_register,
+            .write_register_cb = (ltc2941_ret_t (*)(void *, uint8_t, uint8_t))app_lib_bat_write_register
+        },
+        .config = {
+            .alert_level = LTC2941_ALERT_3_0V,
+            .alert_mode = LTC2941_ALERT_DISABLED,
+            .prescaler = PRESCALER_M
+        }
+    };
+
+    ltc2941_init(&battery_fg);
+
+    for(;;) {
+        uint16_t fg_data = 0x00;
+        ltc2941_read_charge(&battery_fg, &fg_data);
+
+        float percentage = fg_data * MAH_LSB * 100.0 / BATTERY_CAP;
+
+        ESP_LOGI(TAG, "Charge: %.2f", percentage);
+
+        vTaskDelay(pdMS_TO_TICKS(30000));
+    }
+}
\ No newline at end of file
diff --git a/main/app_task_epd.c b/main/app_task_epd.c
index 8e56ea0..0b39a22 100644
--- a/main/app_task_epd.c
+++ b/main/app_task_epd.c
@@ -1,11 +1,39 @@
+#include <string.h>
+
 #include "freertos/FreeRTOS.h"
 #include "freertos/task.h"
 #include "freertos/queue.h"
 
-#include "gdew042t2_epd.h"
+#include "app_lib_epd_impl.h"
 
+static uint8_t frame_data[15000][2];
+static uint8_t current_frame = 0;
+
+TaskHandle_t xTaskEPDExampleHandle = NULL;
 void vTaskEPDExample(void *pvParameters) {
-    for(;;) {
+    app_lib_epd_impl_t epd_impl = {0};
 
+    gd_epd_042_t epd = {
+        .cb = {
+            .write_data_cb = (gd_epd_042_ret_t (*)(void *, uint8_t *, uint32_t))app_lib_epd_impl_write_data,
+            .write_cmd_cb = (gd_epd_042_ret_t (*)(void *, uint8_t *, uint8_t))app_lib_epd_impl_write_cmd,
+            .poll_busy_cb = (gd_epd_042_ret_t (*)(void *))app_lib_epd_impl_poll_busy,
+            .reset_cb = (gd_epd_042_ret_t (*)(void *))app_lib_epd_impl_reset
+        },
+        .user_data = &epd_impl
+    };
+
+    app_lib_epd_impl_init(&epd_impl);
+    gd_epd_042_init(&epd);
+
+    memset(frame_data[current_frame], 0xFF, 15000);
+    memset(frame_data[(~current_frame) & 0x01], 0xFF, 15000);
+
+    gd_epd_042_load(&epd, frame_data[current_frame], frame_data[(~current_frame) & 0x01]);
+    gd_epd_042_update(&epd);
+    gd_epd_042_deepsleep(&epd);
+
+    for(;;) {
+        vTaskDelay(10000);
     }
 }
\ No newline at end of file
diff --git a/main/app_task_led.c b/main/app_task_led.c
index 3bd7539..7371364 100644
--- a/main/app_task_led.c
+++ b/main/app_task_led.c
@@ -8,6 +8,8 @@
 #include "user_board.h"
 
 #define BREATHE_LED_NUM 3
+#define BREATHE_LED_MAXIMUM_BRIGHTNESS 512
+#define BREATHE_LED_CYCLE 2500
 
 TaskHandle_t xTaskLEDsHandle = NULL;
 void vTaskLEDs(void *pvParameters) {
@@ -85,16 +87,17 @@ void vTaskLEDs(void *pvParameters) {
     ledc_fade_func_install(0);
 
     for(;;) {
+        vTaskDelay(pdMS_TO_TICKS(BREATHE_LED_CYCLE));
         ledc_set_fade_with_time(ledc_channels[BREATHE_LED_NUM].speed_mode,
-            ledc_channels[BREATHE_LED_NUM].channel, 1023, 2500);
+            ledc_channels[BREATHE_LED_NUM].channel, BREATHE_LED_MAXIMUM_BRIGHTNESS, BREATHE_LED_CYCLE);
         ledc_fade_start(ledc_channels[BREATHE_LED_NUM].speed_mode,
             ledc_channels[BREATHE_LED_NUM].channel, LEDC_FADE_NO_WAIT);
-        vTaskDelay(pdMS_TO_TICKS(2500));
+        vTaskDelay(pdMS_TO_TICKS(BREATHE_LED_CYCLE));
 
         ledc_set_fade_with_time(ledc_channels[BREATHE_LED_NUM].speed_mode,
-            ledc_channels[BREATHE_LED_NUM].channel, 0, 2500);
+            ledc_channels[BREATHE_LED_NUM].channel, 0, BREATHE_LED_CYCLE);
         ledc_fade_start(ledc_channels[BREATHE_LED_NUM].speed_mode,
             ledc_channels[BREATHE_LED_NUM].channel, LEDC_FADE_NO_WAIT);
-        vTaskDelay(pdMS_TO_TICKS(2500));
+        vTaskDelay(pdMS_TO_TICKS(BREATHE_LED_CYCLE));
     }
 }
\ No newline at end of file
diff --git a/main/lib/gdew042t2_epd.c b/main/lib/gdew042t2_epd.c
index 783762d..394cf0f 100644
--- a/main/lib/gdew042t2_epd.c
+++ b/main/lib/gdew042t2_epd.c
@@ -51,4 +51,4 @@ gd_epd_042_ret_t gd_epd_042_update(gd_epd_042_t *epd) {
 
     epd->cb.poll_busy_cb(epd->user_data);
     return EPD_OK;
-}
\ No newline at end of file
+}
diff --git a/main/lib/gdew042t2_epd.h b/main/lib/gdew042t2_epd.h
index 5818def..064d749 100644
--- a/main/lib/gdew042t2_epd.h
+++ b/main/lib/gdew042t2_epd.h
@@ -21,5 +21,8 @@ typedef struct {
 } gd_epd_042_t;
 
 gd_epd_042_ret_t gd_epd_042_init(gd_epd_042_t *epd);
+gd_epd_042_ret_t gd_epd_042_load(gd_epd_042_t *epd, uint8_t *old_data, uint8_t *new_data);
+gd_epd_042_ret_t gd_epd_042_update(gd_epd_042_t *epd);
+gd_epd_042_ret_t gd_epd_042_deepsleep(gd_epd_042_t *epd);
 
 #endif
\ No newline at end of file
diff --git a/main/lib/htu21d_dht.c b/main/lib/htu21d_dht.c
new file mode 100644
index 0000000..f9ceb1c
--- /dev/null
+++ b/main/lib/htu21d_dht.c
@@ -0,0 +1,6 @@
+#include "htu21d_dht.h"
+
+htu21d_ret_t htu21d_init(htu21d_t *htu) {
+    htu->cb.write_command_cb(htu->user_data, 0xFE, 0x00);
+    return HTU21D_OK;
+}
\ No newline at end of file
diff --git a/main/lib/htu21d_dht.h b/main/lib/htu21d_dht.h
new file mode 100644
index 0000000..246ff80
--- /dev/null
+++ b/main/lib/htu21d_dht.h
@@ -0,0 +1,21 @@
+#ifndef __HTU21D_DHT_H
+#define __HTU21D_DHT_H
+
+#include <stdint.h>
+
+typedef enum {
+    HTU21D_OK,
+    HTU21D_ERROR
+} htu21d_ret_t;
+
+typedef struct {
+    htu21d_ret_t (*write_command_cb)(void * handle, uint8_t reg, uint8_t value);
+    htu21d_ret_t (*read_data_cb)(void *handle, uint8_t reg, uint8_t *value);
+} htu21d_cb_t;
+
+typedef struct {
+    htu21d_cb_t cb;
+    void *user_data;
+} htu21d_t;
+
+#endif
\ No newline at end of file
diff --git a/main/lib/ltc2941_battery.h b/main/lib/ltc2941_battery.h
index 0d3d659..dcca6fb 100644
--- a/main/lib/ltc2941_battery.h
+++ b/main/lib/ltc2941_battery.h
@@ -56,4 +56,8 @@ typedef struct {
 #define LTC2941_STATUS_ALRT_VBAT (1 << 1U)
 #define LTC2941_STATUS_ALRT_UVLO 1U
 
+ltc2941_ret_t ltc2941_init(ltc2941_t *bat);
+ltc2941_ret_t ltc2941_read_status(ltc2941_t *bat, uint8_t *status);
+ltc2941_ret_t ltc2941_read_charge(ltc2941_t *bat, uint16_t *charge);
+
 #endif
\ No newline at end of file
diff --git a/main/main.c b/main/main.c
index 9ee8142..986d75b 100644
--- a/main/main.c
+++ b/main/main.c
@@ -4,16 +4,34 @@
 #include "freertos/task.h"
 #include "freertos/queue.h"
 
+#include "esp_log.h"
+
 #include "driver/gpio.h"
+#include "driver/i2c.h"
+
+#include "user_board.h"
 
 void vTaskLEDs(void *pvParameters);
 extern TaskHandle_t xTaskLEDsHandle;
 
+void vTasBatteryExample(void *pvParameters);
+extern TaskHandle_t xTaskBatteryExampleHandle;
+
+extern TaskHandle_t xTaskEPDExampleHandle;
+void vTaskEPDExample(void *pvParameters);
+
 void app_lib_i2c_system_init(void);
 
+static const char *TAG = "APP_MAIN";
+
 void app_main(void) {
+    // Init system peripherals.
     app_lib_i2c_system_init();
+
+    // Init tasks
     xTaskCreate(vTaskLEDs, "TASK_LEDs", 1024, NULL, 4, &xTaskLEDsHandle);
+    xTaskCreate(vTasBatteryExample, "TASK_BAT", 2048, NULL, 4, &xTaskBatteryExampleHandle);
+    xTaskCreate(vTaskEPDExample, "TASK_EPD", 2048, NULL, 4, &xTaskEPDExampleHandle);
 
     for(;;) {
         vTaskSuspend(NULL);
diff --git a/main/user_board.h b/main/user_board.h
index 3e2e40a..3c7b03e 100644
--- a/main/user_board.h
+++ b/main/user_board.h
@@ -16,4 +16,11 @@
 #define BOARD_SYSTEM_I2C_SDA_PIN GPIO_NUM_39
 #define BOARD_SYSTEM_I2C_SCL_PIN GPIO_NUM_40
 
+#define BOARD_EPD_SPI_CS_PIN   GPIO_NUM_13
+#define BOARD_EPD_SPI_MOSI_PIN GPIO_NUM_15
+#define BOARD_EPD_SPI_SCK_PIN  GPIO_NUM_14
+#define BOARD_EPD_RES_PIN      GPIO_NUM_10
+#define BOARD_EPD_DC_PIN       GPIO_NUM_12
+#define BOARD_EPD_BUSY_PIN     GPIO_NUM_11
+
 #endif
\ No newline at end of file