diff --git a/esphomeyaml/__main__.py b/esphomeyaml/__main__.py
index 94ac0c30ea..aea995a142 100644
--- a/esphomeyaml/__main__.py
+++ b/esphomeyaml/__main__.py
@@ -139,7 +139,7 @@ def write_cpp(config):
     ini_path = os.path.join(get_base_path(config), 'platformio.ini')
     writer.write_platformio_ini(platformio_ini_s, ini_path)
 
-    code_s = indent('\n'.join(all_code))
+    code_s = indent('\n'.join(line.rstrip() for line in all_code))
     cpp_path = os.path.join(get_base_path(config), 'src', 'main.cpp')
     writer.write_cpp(code_s, cpp_path)
     return 0
diff --git a/esphomeyaml/components/ads1115.py b/esphomeyaml/components/ads1115.py
index 7204ca6cf4..bee0d1191f 100644
--- a/esphomeyaml/components/ads1115.py
+++ b/esphomeyaml/components/ads1115.py
@@ -37,5 +37,4 @@ def to_code(config):
             add(ads1115.set_rate(RawExpression(RATES[conf[CONF_RATE]])))
 
 
-def build_flags(config):
-    return '-DUSE_ADS1115_SENSOR'
+BUILD_FLAGS = '-DUSE_ADS1115_SENSOR'
diff --git a/esphomeyaml/components/binary_sensor/__init__.py b/esphomeyaml/components/binary_sensor/__init__.py
index 05371135f7..b8449353c2 100644
--- a/esphomeyaml/components/binary_sensor/__init__.py
+++ b/esphomeyaml/components/binary_sensor/__init__.py
@@ -35,5 +35,4 @@ def setup_mqtt_binary_sensor(obj, config):
     setup_mqtt_component(obj, config)
 
 
-def build_flags(config):
-    return '-DUSE_BINARY_SENSOR'
+BUILD_FLAGS = '-DUSE_BINARY_SENSOR'
diff --git a/esphomeyaml/components/binary_sensor/gpio.py b/esphomeyaml/components/binary_sensor/gpio.py
index 20ccb31814..c4e362aa13 100644
--- a/esphomeyaml/components/binary_sensor/gpio.py
+++ b/esphomeyaml/components/binary_sensor/gpio.py
@@ -21,5 +21,4 @@ def to_code(config):
     binary_sensor.setup_mqtt_binary_sensor(gpio.Pmqtt, config)
 
 
-def build_flags(config):
-    return '-DUSE_GPIO_BINARY_SENSOR'
+BUILD_FLAGS = '-DUSE_GPIO_BINARY_SENSOR'
diff --git a/esphomeyaml/components/binary_sensor/status.py b/esphomeyaml/components/binary_sensor/status.py
index 749f0f72dc..5a48e1e674 100644
--- a/esphomeyaml/components/binary_sensor/status.py
+++ b/esphomeyaml/components/binary_sensor/status.py
@@ -17,5 +17,4 @@ def to_code(config):
     binary_sensor.setup_mqtt_binary_sensor(status.Pmqtt, config)
 
 
-def build_flags(config):
-    return '-DUSE_STATUS_BINARY_SENSOR'
+BUILD_FLAGS = '-DUSE_STATUS_BINARY_SENSOR'
diff --git a/esphomeyaml/components/dallas.py b/esphomeyaml/components/dallas.py
index 752c0ce7e6..850aaafd15 100644
--- a/esphomeyaml/components/dallas.py
+++ b/esphomeyaml/components/dallas.py
@@ -20,5 +20,4 @@ def to_code(config):
         Pvariable(DALLAS_COMPONENT_CLASS, conf[CONF_ID], rhs)
 
 
-def build_flags(config):
-    return '-DUSE_DALLAS_SENSOR'
+BUILD_FLAGS = '-DUSE_DALLAS_SENSOR'
diff --git a/esphomeyaml/components/debug.py b/esphomeyaml/components/debug.py
index c20969dc4c..533ffb8114 100644
--- a/esphomeyaml/components/debug.py
+++ b/esphomeyaml/components/debug.py
@@ -11,5 +11,4 @@ def to_code(config):
     add(App.make_debug_component())
 
 
-def build_flags(config):
-    return '-DUSE_DEBUG_COMPONENT'
+BUILD_FLAGS = '-DUSE_DEBUG_COMPONENT'
diff --git a/esphomeyaml/components/deep_sleep.py b/esphomeyaml/components/deep_sleep.py
index c89db90457..c76205dd8d 100644
--- a/esphomeyaml/components/deep_sleep.py
+++ b/esphomeyaml/components/deep_sleep.py
@@ -38,5 +38,4 @@ def to_code(config):
         add(deep_sleep.set_run_duration(config[CONF_RUN_DURATION]))
 
 
-def build_flags(config):
-    return '-DUSE_DEEP_SLEEP'
+BUILD_FLAGS = '-DUSE_DEEP_SLEEP'
diff --git a/esphomeyaml/components/fan/__init__.py b/esphomeyaml/components/fan/__init__.py
index ddf4861da4..ef25200267 100644
--- a/esphomeyaml/components/fan/__init__.py
+++ b/esphomeyaml/components/fan/__init__.py
@@ -23,5 +23,4 @@ def setup_mqtt_fan(obj, config):
     setup_mqtt_component(obj, config)
 
 
-def build_flags(config):
-    return '-DUSE_FAN'
+BUILD_FLAGS = '-DUSE_FAN'
diff --git a/esphomeyaml/components/i2c.py b/esphomeyaml/components/i2c.py
index 459f29e7c2..870ff6efca 100644
--- a/esphomeyaml/components/i2c.py
+++ b/esphomeyaml/components/i2c.py
@@ -2,19 +2,23 @@ import voluptuous as vol
 
 import esphomeyaml.config_validation as cv
 from esphomeyaml import pins
-from esphomeyaml.const import CONF_FREQUENCY, CONF_SCL, CONF_SDA
-from esphomeyaml.helpers import App, add
+from esphomeyaml.const import CONF_FREQUENCY, CONF_SCL, CONF_SDA, CONF_SCAN, CONF_ID
+from esphomeyaml.helpers import App, add, Pvariable
 
 CONFIG_SCHEMA = vol.Schema({
+    cv.GenerateID('i2c'): cv.register_variable_id,
     vol.Required(CONF_SDA, default='SDA'): pins.input_output_pin,
     vol.Required(CONF_SCL, default='SCL'): pins.input_output_pin,
     vol.Optional(CONF_FREQUENCY): vol.All(cv.only_on_esp32, cv.positive_int),
+    vol.Optional(CONF_SCAN): cv.boolean,
 })
 
 
 def to_code(config):
-    add(App.init_i2c(config[CONF_SDA], config[CONF_SCL], config.get(CONF_FREQUENCY)))
+    rhs = App.init_i2c(config[CONF_SDA], config[CONF_SCL], config.get(CONF_SCAN))
+    i2c = Pvariable('I2CComponent', config[CONF_ID], rhs)
+    if CONF_FREQUENCY in config:
+        add(i2c.set_frequency(config[CONF_FREQUENCY]))
 
 
-def build_flags(config):
-    return '-DUSE_I2C'
+BUILD_FLAGS = '-DUSE_I2C'
diff --git a/esphomeyaml/components/ir_transmitter.py b/esphomeyaml/components/ir_transmitter.py
index b1be71bf29..4d9f972380 100644
--- a/esphomeyaml/components/ir_transmitter.py
+++ b/esphomeyaml/components/ir_transmitter.py
@@ -23,5 +23,4 @@ def to_code(config):
         Pvariable(IR_TRANSMITTER_COMPONENT_CLASS, conf[CONF_ID], rhs)
 
 
-def build_flags(config):
-    return '-DUSE_IR_TRANSMITTER'
+BUILD_FLAGS = '-DUSE_IR_TRANSMITTER'
diff --git a/esphomeyaml/components/light/__init__.py b/esphomeyaml/components/light/__init__.py
index 8ac678537a..1675a56292 100644
--- a/esphomeyaml/components/light/__init__.py
+++ b/esphomeyaml/components/light/__init__.py
@@ -12,5 +12,4 @@ def setup_light_component(obj, config):
         add(obj.set_default_transition_length(config[CONF_DEFAULT_TRANSITION_LENGTH]))
 
 
-def build_flags(config):
-    return '-DUSE_LIGHT'
+BUILD_FLAGS = '-DUSE_LIGHT'
diff --git a/esphomeyaml/components/mqtt.py b/esphomeyaml/components/mqtt.py
index ee216da8da..2ba4d42b1e 100644
--- a/esphomeyaml/components/mqtt.py
+++ b/esphomeyaml/components/mqtt.py
@@ -6,15 +6,26 @@ import esphomeyaml.config_validation as cv
 from esphomeyaml.const import CONF_BIRTH_MESSAGE, CONF_BROKER, CONF_CLIENT_ID, CONF_DISCOVERY, \
     CONF_DISCOVERY_PREFIX, CONF_DISCOVERY_RETAIN, CONF_SSL_FINGERPRINTS, CONF_ID, CONF_LOG_TOPIC, \
     CONF_MQTT, CONF_PASSWORD, CONF_PAYLOAD, CONF_PORT, CONF_QOS, CONF_RETAIN, CONF_TOPIC, \
-    CONF_TOPIC_PREFIX, CONF_USERNAME, CONF_WILL_MESSAGE
+    CONF_TOPIC_PREFIX, CONF_USERNAME, CONF_WILL_MESSAGE, CONF_KEEPALIVE
 from esphomeyaml.helpers import App, ArrayInitializer, Pvariable, StructInitializer, add, \
     exp_empty_optional, RawExpression
 
-MQTT_WILL_BIRTH_SCHEMA = vol.Any(None, vol.Schema({
+
+def validate_message_just_topic(value):
+    value = cv.publish_topic(value)
+    return {CONF_TOPIC: value}
+
+
+MQTT_MESSAGE_BASE = vol.Schema({
     vol.Required(CONF_TOPIC): cv.publish_topic,
-    vol.Required(CONF_PAYLOAD): cv.mqtt_payload,
     vol.Optional(CONF_QOS, default=0): vol.All(vol.Coerce(int), vol.In([0, 1, 2])),
     vol.Optional(CONF_RETAIN, default=True): cv.boolean,
+})
+
+MQTT_MESSAGE_TEMPLATE_SCHEMA = vol.Any(None, MQTT_MESSAGE_BASE, validate_message_just_topic)
+
+MQTT_MESSAGE_SCHEMA = vol.Any(None, MQTT_MESSAGE_BASE.extend({
+    vol.Required(CONF_PAYLOAD): cv.mqtt_payload,
 }))
 
 
@@ -47,12 +58,13 @@ CONFIG_SCHEMA = vol.Schema({
     vol.Optional(CONF_DISCOVERY): cv.boolean,
     vol.Optional(CONF_DISCOVERY_RETAIN): cv.boolean,
     vol.Optional(CONF_DISCOVERY_PREFIX): cv.publish_topic,
-    vol.Optional(CONF_BIRTH_MESSAGE): MQTT_WILL_BIRTH_SCHEMA,
-    vol.Optional(CONF_WILL_MESSAGE): MQTT_WILL_BIRTH_SCHEMA,
+    vol.Optional(CONF_BIRTH_MESSAGE): MQTT_MESSAGE_SCHEMA,
+    vol.Optional(CONF_WILL_MESSAGE): MQTT_MESSAGE_SCHEMA,
     vol.Optional(CONF_TOPIC_PREFIX): cv.publish_topic,
-    vol.Optional(CONF_LOG_TOPIC): cv.publish_topic,
+    vol.Optional(CONF_LOG_TOPIC): MQTT_MESSAGE_TEMPLATE_SCHEMA,
     vol.Optional(CONF_SSL_FINGERPRINTS): vol.All(cv.only_on_esp8266,
                                                  cv.ensure_list, [validate_fingerprint]),
+    vol.Optional(CONF_KEEPALIVE): vol.All(cv.positive_time_period, cv.time_period_to_seconds)
 })
 
 
@@ -62,7 +74,7 @@ def exp_mqtt_message(config):
     exp = StructInitializer(
         'mqtt::MQTTMessage',
         ('topic', config[CONF_TOPIC]),
-        ('payload', config[CONF_PAYLOAD]),
+        ('payload', config.get(CONF_PAYLOAD, "")),
         ('qos', config[CONF_QOS]),
         ('retain', config[CONF_RETAIN])
     )
@@ -79,20 +91,34 @@ def to_code(config):
         discovery_retain = config.get(CONF_DISCOVERY_RETAIN, True)
         discovery_prefix = config.get(CONF_DISCOVERY_PREFIX, 'homeassistant')
         add(mqtt.set_discovery_info(discovery_prefix, discovery_retain))
-    if CONF_BIRTH_MESSAGE in config:
-        add(mqtt.set_birth_message(config[CONF_BIRTH_MESSAGE]))
-    if CONF_WILL_MESSAGE in config:
-        add(mqtt.set_last_will(config[CONF_WILL_MESSAGE]))
     if CONF_TOPIC_PREFIX in config:
         add(mqtt.set_topic_prefix(config[CONF_TOPIC_PREFIX]))
+    if CONF_BIRTH_MESSAGE in config:
+        birth_message = config[CONF_BIRTH_MESSAGE]
+        if birth_message is None:
+            add(mqtt.disable_birth_message())
+        else:
+            add(mqtt.set_birth_message(exp_mqtt_message(birth_message)))
+    if CONF_WILL_MESSAGE in config:
+        will_message = config[CONF_WILL_MESSAGE]
+        if will_message is None:
+            add(mqtt.disable_last_will())
+        else:
+            add(mqtt.set_last_will(exp_mqtt_message(will_message)))
     if CONF_CLIENT_ID in config:
         add(mqtt.set_client_id(config[CONF_CLIENT_ID]))
     if CONF_LOG_TOPIC in config:
-        add(mqtt.set_log_topic(config[CONF_LOG_TOPIC]))
+        log_topic = config[CONF_LOG_TOPIC]
+        if log_topic is None:
+            add(mqtt.disable_log_message())
+        else:
+            add(mqtt.set_log_topic(exp_mqtt_message(log_topic)))
     if CONF_SSL_FINGERPRINTS in config:
         for fingerprint in config[CONF_SSL_FINGERPRINTS]:
             arr = [RawExpression("0x{}".format(fingerprint[i:i + 2])) for i in range(0, 40, 2)]
             add(mqtt.add_ssl_fingerprint(ArrayInitializer(*arr, multiline=False)))
+    if CONF_KEEPALIVE in config:
+        add(mqtt.set_keep_alive(config[CONF_KEEPALIVE]))
 
 
 def required_build_flags(config):
diff --git a/esphomeyaml/components/ota.py b/esphomeyaml/components/ota.py
index dd50810de9..59f14b1970 100644
--- a/esphomeyaml/components/ota.py
+++ b/esphomeyaml/components/ota.py
@@ -45,5 +45,4 @@ def get_auth(config):
     return config[CONF_OTA].get(CONF_PASSWORD, '')
 
 
-def build_flags(config):
-    return '-DUSE_OTA'
+BUILD_FLAGS = '-DUSE_OTA'
diff --git a/esphomeyaml/components/output/__init__.py b/esphomeyaml/components/output/__init__.py
index 2cc957d243..c4f29fd6b1 100644
--- a/esphomeyaml/components/output/__init__.py
+++ b/esphomeyaml/components/output/__init__.py
@@ -25,5 +25,4 @@ def setup_output_platform(obj, config, skip_power_supply=False):
         add(obj.set_max_power(config[CONF_MAX_POWER]))
 
 
-def build_flags(config):
-    return '-DUSE_OUTPUT'
+BUILD_FLAGS = '-DUSE_OUTPUT'
diff --git a/esphomeyaml/components/output/esp8266_pwm.py b/esphomeyaml/components/output/esp8266_pwm.py
index 4d299d4e62..c89db95604 100644
--- a/esphomeyaml/components/output/esp8266_pwm.py
+++ b/esphomeyaml/components/output/esp8266_pwm.py
@@ -28,5 +28,4 @@ def to_code(config):
     output.setup_output_platform(gpio, config)
 
 
-def build_flags(config):
-    return '-DUSE_ESP8266_PWM_OUTPUT'
+BUILD_FLAGS = '-DUSE_ESP8266_PWM_OUTPUT'
diff --git a/esphomeyaml/components/output/gpio.py b/esphomeyaml/components/output/gpio.py
index 82f250c4cb..0a4d11248d 100644
--- a/esphomeyaml/components/output/gpio.py
+++ b/esphomeyaml/components/output/gpio.py
@@ -17,5 +17,4 @@ def to_code(config):
     output.setup_output_platform(gpio, config)
 
 
-def build_flags(config):
-    return '-DUSE_GPIO_OUTPUT'
+BUILD_FLAGS = '-DUSE_GPIO_OUTPUT'
diff --git a/esphomeyaml/components/output/ledc.py b/esphomeyaml/components/output/ledc.py
index f4076fd0fb..f6c8dd5c01 100644
--- a/esphomeyaml/components/output/ledc.py
+++ b/esphomeyaml/components/output/ledc.py
@@ -38,5 +38,4 @@ def to_code(config):
     output.setup_output_platform(ledc, config)
 
 
-def build_flags(config):
-    return '-DUSE_LEDC_OUTPUT'
+BUILD_FLAGS = '-DUSE_LEDC_OUTPUT'
diff --git a/esphomeyaml/components/output/pca9685.py b/esphomeyaml/components/output/pca9685.py
index fd29bc85c8..ffa8453280 100644
--- a/esphomeyaml/components/output/pca9685.py
+++ b/esphomeyaml/components/output/pca9685.py
@@ -25,5 +25,4 @@ def to_code(config):
     output.setup_output_platform(out, config, skip_power_supply=True)
 
 
-def build_flags(config):
-    return '-DUSE_PCA9685_OUTPUT'
+BUILD_FLAGS = '-DUSE_PCA9685_OUTPUT'
diff --git a/esphomeyaml/components/pca9685.py b/esphomeyaml/components/pca9685.py
index 5d40b8918f..5db5c065a1 100644
--- a/esphomeyaml/components/pca9685.py
+++ b/esphomeyaml/components/pca9685.py
@@ -33,5 +33,4 @@ def to_code(config):
             add(pca9685.set_phase_balancer(phase_balancer))
 
 
-def build_flags(config):
-    return '-DUSE_PCA9685_OUTPUT'
+BUILD_FLAGS = '-DUSE_PCA9685_OUTPUT'
diff --git a/esphomeyaml/components/pcf8574.py b/esphomeyaml/components/pcf8574.py
new file mode 100644
index 0000000000..82be871292
--- /dev/null
+++ b/esphomeyaml/components/pcf8574.py
@@ -0,0 +1,24 @@
+import voluptuous as vol
+
+import esphomeyaml.config_validation as cv
+from esphomeyaml.const import CONF_ADDRESS, CONF_ID, CONF_PCF8575
+from esphomeyaml.helpers import App, Pvariable
+
+DEPENDENCIES = ['i2c']
+
+PCF8574_SCHEMA = vol.Schema({
+    vol.Required(CONF_ID): cv.register_variable_id,
+    vol.Optional(CONF_ADDRESS, default=0x21): cv.i2c_address,
+    vol.Optional(CONF_PCF8575, default=False): cv.boolean,
+})
+
+CONFIG_SCHEMA = vol.All(cv.ensure_list, [PCF8574_SCHEMA])
+
+
+def to_code(config):
+    for conf in config:
+        rhs = App.make_pcf8574_component(conf[CONF_ADDRESS], conf[CONF_PCF8575])
+        Pvariable('io::PCF8574Component', conf[CONF_ID], rhs)
+
+
+BUILD_FLAGS = '-DUSE_PCF8574'
diff --git a/esphomeyaml/components/power_supply.py b/esphomeyaml/components/power_supply.py
index 7cf8496210..8e06a16758 100644
--- a/esphomeyaml/components/power_supply.py
+++ b/esphomeyaml/components/power_supply.py
@@ -25,5 +25,4 @@ def to_code(config):
             add(psu.set_keep_on_time(conf[CONF_KEEP_ON_TIME]))
 
 
-def build_flags(config):
-    return '-DUSE_OUTPUT'
+BUILD_FLAGS = '-DUSE_OUTPUT'
diff --git a/esphomeyaml/components/sensor/__init__.py b/esphomeyaml/components/sensor/__init__.py
index 870fdb1a72..c72add513e 100644
--- a/esphomeyaml/components/sensor/__init__.py
+++ b/esphomeyaml/components/sensor/__init__.py
@@ -104,5 +104,4 @@ def register_sensor(var, config):
     setup_mqtt_sensor_component(mqtt_sensor, config)
 
 
-def build_flags(config):
-    return '-DUSE_SENSOR'
+BUILD_FLAGS = '-DUSE_SENSOR'
diff --git a/esphomeyaml/components/sensor/adc.py b/esphomeyaml/components/sensor/adc.py
index e11d80b8fb..14d309eb2e 100644
--- a/esphomeyaml/components/sensor/adc.py
+++ b/esphomeyaml/components/sensor/adc.py
@@ -36,5 +36,4 @@ def to_code(config):
     sensor.setup_mqtt_sensor_component(make.Pmqtt, config)
 
 
-def build_flags(config):
-    return '-DUSE_ADC_SENSOR'
+BUILD_FLAGS = '-DUSE_ADC_SENSOR'
diff --git a/esphomeyaml/components/sensor/ads1115.py b/esphomeyaml/components/sensor/ads1115.py
index 5572b73e81..3b663232d7 100644
--- a/esphomeyaml/components/sensor/ads1115.py
+++ b/esphomeyaml/components/sensor/ads1115.py
@@ -59,5 +59,4 @@ def to_code(config):
     sensor.register_sensor(sensor_, config)
 
 
-def build_flags(config):
-    return '-DUSE_ADS1115_SENSOR'
+BUILD_FLAGS = '-DUSE_ADS1115_SENSOR'
diff --git a/esphomeyaml/components/sensor/bmp085.py b/esphomeyaml/components/sensor/bmp085.py
index 50fc5134ce..3dc9b135be 100644
--- a/esphomeyaml/components/sensor/bmp085.py
+++ b/esphomeyaml/components/sensor/bmp085.py
@@ -31,5 +31,4 @@ def to_code(config):
     sensor.setup_mqtt_sensor_component(bmp.Pmqtt_pressure, config[CONF_PRESSURE])
 
 
-def build_flags(config):
-    return '-DUSE_BMP085_SENSOR'
+BUILD_FLAGS = '-DUSE_BMP085_SENSOR'
diff --git a/esphomeyaml/components/sensor/dallas.py b/esphomeyaml/components/sensor/dallas.py
index 83bfb6dd44..3bf4127815 100644
--- a/esphomeyaml/components/sensor/dallas.py
+++ b/esphomeyaml/components/sensor/dallas.py
@@ -34,5 +34,4 @@ def to_code(config):
     sensor.register_sensor(sensor_, config)
 
 
-def build_flags(config):
-    return '-DUSE_DALLAS_SENSOR'
+BUILD_FLAGS = '-DUSE_DALLAS_SENSOR'
diff --git a/esphomeyaml/components/sensor/dht.py b/esphomeyaml/components/sensor/dht.py
index cbccabaab2..9712040c3c 100644
--- a/esphomeyaml/components/sensor/dht.py
+++ b/esphomeyaml/components/sensor/dht.py
@@ -34,5 +34,4 @@ def to_code(config):
     sensor.setup_mqtt_sensor_component(dht.Pmqtt_humidity, config[CONF_HUMIDITY])
 
 
-def build_flags(config):
-    return '-DUSE_DHT_SENSOR'
+BUILD_FLAGS = '-DUSE_DHT_SENSOR'
diff --git a/esphomeyaml/components/sensor/hdc1080.py b/esphomeyaml/components/sensor/hdc1080.py
index 24a45f7af2..3b29bf7e24 100644
--- a/esphomeyaml/components/sensor/hdc1080.py
+++ b/esphomeyaml/components/sensor/hdc1080.py
@@ -28,5 +28,4 @@ def to_code(config):
     sensor.setup_mqtt_sensor_component(hdc1080.Pmqtt_humidity, config[CONF_HUMIDITY])
 
 
-def build_flags(config):
-    return '-DUSE_HDC1080_SENSOR'
+BUILD_FLAGS = '-DUSE_HDC1080_SENSOR'
diff --git a/esphomeyaml/components/sensor/htu21d.py b/esphomeyaml/components/sensor/htu21d.py
index c532060cc7..3ec4e50b32 100644
--- a/esphomeyaml/components/sensor/htu21d.py
+++ b/esphomeyaml/components/sensor/htu21d.py
@@ -28,5 +28,4 @@ def to_code(config):
     sensor.setup_mqtt_sensor_component(htu21d.Pmqtt_humidity, config[CONF_HUMIDITY])
 
 
-def build_flags(config):
-    return '-DUSE_HTU21D_SENSOR'
+BUILD_FLAGS = '-DUSE_HTU21D_SENSOR'
diff --git a/esphomeyaml/components/sensor/mpu6050.py b/esphomeyaml/components/sensor/mpu6050.py
new file mode 100644
index 0000000000..38d63c3861
--- /dev/null
+++ b/esphomeyaml/components/sensor/mpu6050.py
@@ -0,0 +1,73 @@
+import voluptuous as vol
+
+import esphomeyaml.config_validation as cv
+from esphomeyaml.components import sensor
+from esphomeyaml.components.sensor import MQTT_SENSOR_ID_SCHEMA
+from esphomeyaml.const import CONF_ADDRESS, CONF_ID, CONF_MQTT_ID, CONF_NAME, CONF_TEMPERATURE, \
+    CONF_UPDATE_INTERVAL
+from esphomeyaml.helpers import App, Pvariable
+
+DEPENDENCIES = ['i2c']
+
+CONF_ACCEL_X = 'accel_x'
+CONF_ACCEL_Y = 'accel_y'
+CONF_ACCEL_Z = 'accel_z'
+CONF_GYRO_X = 'gyro_x'
+CONF_GYRO_Y = 'gyro_y'
+CONF_GYRO_Z = 'gyro_z'
+
+PLATFORM_SCHEMA = sensor.PLATFORM_SCHEMA.extend({
+    cv.GenerateID('mpu6050'): cv.register_variable_id,
+    vol.Optional(CONF_ADDRESS, default=0x68): cv.i2c_address,
+    vol.Optional(CONF_ACCEL_X): MQTT_SENSOR_ID_SCHEMA,
+    vol.Optional(CONF_ACCEL_Y): MQTT_SENSOR_ID_SCHEMA,
+    vol.Optional(CONF_ACCEL_Z): MQTT_SENSOR_ID_SCHEMA,
+    vol.Optional(CONF_GYRO_X): MQTT_SENSOR_ID_SCHEMA,
+    vol.Optional(CONF_GYRO_Y): MQTT_SENSOR_ID_SCHEMA,
+    vol.Optional(CONF_GYRO_Z): MQTT_SENSOR_ID_SCHEMA,
+    vol.Optional(CONF_TEMPERATURE): MQTT_SENSOR_ID_SCHEMA,
+    vol.Optional(CONF_UPDATE_INTERVAL): cv.positive_not_null_time_period,
+})
+
+
+def to_code(config):
+    rhs = App.make_mpu6050_sensor(config[CONF_ADDRESS], config.get(CONF_UPDATE_INTERVAL))
+    mpu = Pvariable('sensor::MPU6050Component', config[CONF_ID], rhs)
+    if CONF_ACCEL_X in config:
+        conf = config[CONF_ACCEL_X]
+        rhs = mpu.Pmake_accel_x_sensor(conf[CONF_NAME])
+        sensor_ = Pvariable('sensor::MPU6050AccelSensor', conf[CONF_MQTT_ID], rhs)
+        sensor.register_sensor(sensor_, conf)
+    if CONF_ACCEL_Y in config:
+        conf = config[CONF_ACCEL_Y]
+        rhs = mpu.Pmake_accel_y_sensor(conf[CONF_NAME])
+        sensor_ = Pvariable('sensor::MPU6050AccelSensor', conf[CONF_MQTT_ID], rhs)
+        sensor.register_sensor(sensor_, conf)
+    if CONF_ACCEL_Z in config:
+        conf = config[CONF_ACCEL_Z]
+        rhs = mpu.Pmake_accel_z_sensor(conf[CONF_NAME])
+        sensor_ = Pvariable('sensor::MPU6050AccelSensor', conf[CONF_MQTT_ID], rhs)
+        sensor.register_sensor(sensor_, conf)
+    if CONF_GYRO_X in config:
+        conf = config[CONF_GYRO_X]
+        rhs = mpu.Pmake_gyro_x_sensor(conf[CONF_NAME])
+        sensor_ = Pvariable('sensor::MPU6050GyroSensor', conf[CONF_MQTT_ID], rhs)
+        sensor.register_sensor(sensor_, conf)
+    if CONF_GYRO_Y in config:
+        conf = config[CONF_GYRO_Y]
+        rhs = mpu.Pmake_gyro_y_sensor(conf[CONF_NAME])
+        sensor_ = Pvariable('sensor::MPU6050GyroSensor', conf[CONF_MQTT_ID], rhs)
+        sensor.register_sensor(sensor_, conf)
+    if CONF_GYRO_Z in config:
+        conf = config[CONF_GYRO_Z]
+        rhs = mpu.Pmake_gyro_z_sensor(conf[CONF_NAME])
+        sensor_ = Pvariable('sensor::MPU6050GyroSensor', conf[CONF_MQTT_ID], rhs)
+        sensor.register_sensor(sensor_, conf)
+    if CONF_TEMPERATURE in config:
+        conf = config[CONF_TEMPERATURE]
+        rhs = mpu.Pmake_temperature_sensor(conf[CONF_NAME])
+        sensor_ = Pvariable('sensor::MPU6050TemperatureSensor', conf[CONF_MQTT_ID], rhs)
+        sensor.register_sensor(sensor_, conf)
+
+
+BUILD_FLAGS = '-DUSE_MPU6050'
diff --git a/esphomeyaml/components/sensor/pulse_counter.py b/esphomeyaml/components/sensor/pulse_counter.py
index 38027f9963..3329f3ce25 100644
--- a/esphomeyaml/components/sensor/pulse_counter.py
+++ b/esphomeyaml/components/sensor/pulse_counter.py
@@ -59,5 +59,4 @@ def to_code(config):
     sensor.setup_mqtt_sensor_component(make.Pmqtt, config)
 
 
-def build_flags(config):
-    return '-DUSE_PULSE_COUNTER_SENSOR'
+BUILD_FLAGS = '-DUSE_PULSE_COUNTER_SENSOR'
diff --git a/esphomeyaml/components/sensor/ultrasonic.py b/esphomeyaml/components/sensor/ultrasonic.py
index f227cd918d..357b771e5f 100644
--- a/esphomeyaml/components/sensor/ultrasonic.py
+++ b/esphomeyaml/components/sensor/ultrasonic.py
@@ -33,5 +33,4 @@ def to_code(config):
     sensor.setup_mqtt_sensor_component(make.Pmqtt, config)
 
 
-def build_flags(config):
-    return '-DUSE_ULTRASONIC_SENSOR'
+BUILD_FLAGS = '-DUSE_ULTRASONIC_SENSOR'
diff --git a/esphomeyaml/components/switch/__init__.py b/esphomeyaml/components/switch/__init__.py
index 234a4964bb..2ff6f13786 100644
--- a/esphomeyaml/components/switch/__init__.py
+++ b/esphomeyaml/components/switch/__init__.py
@@ -33,5 +33,4 @@ def register_switch(var, config):
     setup_mqtt_switch(mqtt_switch, config)
 
 
-def build_flags(config):
-    return '-DUSE_SWITCH'
+BUILD_FLAGS = '-DUSE_SWITCH'
diff --git a/esphomeyaml/components/switch/gpio.py b/esphomeyaml/components/switch/gpio.py
index 6b2eaf7294..e37872c6c8 100644
--- a/esphomeyaml/components/switch/gpio.py
+++ b/esphomeyaml/components/switch/gpio.py
@@ -19,5 +19,4 @@ def to_code(config):
     switch.setup_mqtt_switch(gpio.Pmqtt, config)
 
 
-def build_flags(config):
-    return '-DUSE_GPIO_SWITCH'
+BUILD_FLAGS = '-DUSE_GPIO_SWITCH'
diff --git a/esphomeyaml/components/switch/ir_transmitter.py b/esphomeyaml/components/switch/ir_transmitter.py
index fa5f31907f..d73e4e83dc 100644
--- a/esphomeyaml/components/switch/ir_transmitter.py
+++ b/esphomeyaml/components/switch/ir_transmitter.py
@@ -92,5 +92,4 @@ def to_code(config):
     switch.register_switch(switch_, config)
 
 
-def build_flags(config):
-    return '-DUSE_IR_TRANSMITTER'
+BUILD_FLAGS = '-DUSE_IR_TRANSMITTER'
diff --git a/esphomeyaml/components/switch/output.py b/esphomeyaml/components/switch/output.py
new file mode 100644
index 0000000000..863e11a3e1
--- /dev/null
+++ b/esphomeyaml/components/switch/output.py
@@ -0,0 +1,22 @@
+import voluptuous as vol
+
+import esphomeyaml.config_validation as cv
+from esphomeyaml.components import switch
+from esphomeyaml.const import CONF_ID, CONF_NAME
+from esphomeyaml.helpers import App, get_variable, variable
+
+PLATFORM_SCHEMA = switch.PLATFORM_SCHEMA.extend({
+    cv.GenerateID('output_switch'): cv.register_variable_id,
+    vol.Required(CONF_ID): cv.variable_id,
+}).extend(switch.MQTT_SWITCH_SCHEMA.schema)
+
+
+def to_code(config):
+    output = get_variable(config[CONF_ID])
+    rhs = App.make_simple_switch(config[CONF_NAME], output)
+    gpio = variable('Application::MakeSimpleSwitch', config[CONF_ID], rhs)
+    switch.setup_switch(gpio.Pswitch_, config)
+    switch.setup_mqtt_switch(gpio.Pmqtt, config)
+
+
+BUILD_FLAGS = '-DUSE_SIMPLE_SWITCH'
diff --git a/esphomeyaml/components/switch/restart.py b/esphomeyaml/components/switch/restart.py
index a21fc716e2..57f53a4e87 100644
--- a/esphomeyaml/components/switch/restart.py
+++ b/esphomeyaml/components/switch/restart.py
@@ -15,5 +15,4 @@ def to_code(config):
     switch.setup_mqtt_switch(restart.Pmqtt, config)
 
 
-def build_flags(config):
-    return '-DUSE_RESTART_SWITCH'
+BUILD_FLAGS = '-DUSE_RESTART_SWITCH'
diff --git a/esphomeyaml/components/switch/shutdown.py b/esphomeyaml/components/switch/shutdown.py
new file mode 100644
index 0000000000..0f451ea6e8
--- /dev/null
+++ b/esphomeyaml/components/switch/shutdown.py
@@ -0,0 +1,19 @@
+import esphomeyaml.config_validation as cv
+from esphomeyaml.components import switch
+from esphomeyaml.const import CONF_ID, CONF_NAME
+from esphomeyaml.helpers import App, variable
+
+PLATFORM_SCHEMA = switch.PLATFORM_SCHEMA.extend({
+    cv.GenerateID('shutdown_switch'): cv.register_variable_id,
+}).extend(switch.MQTT_SWITCH_SCHEMA.schema)
+
+
+def to_code(config):
+    rhs = App.make_shutdown_switch(config[CONF_NAME])
+    shutdown = variable('Application::MakeShutdownSwitch', config[CONF_ID],
+                        rhs)
+    switch.setup_switch(shutdown.Pshutdown, config)
+    switch.setup_mqtt_switch(shutdown.Pmqtt, config)
+
+
+BUILD_FLAGS = '-DUSE_SHUTDOWN_SWITCH'
diff --git a/esphomeyaml/components/web_server.py b/esphomeyaml/components/web_server.py
index 3eff1b8160..486ebfdc85 100644
--- a/esphomeyaml/components/web_server.py
+++ b/esphomeyaml/components/web_server.py
@@ -25,5 +25,4 @@ def to_code(config):
         add(web_server.set_js_url(config[CONF_JS_URL]))
 
 
-def build_flags(config):
-    return '-DUSE_WEB_SERVER'
+BUILD_FLAGS = '-DUSE_WEB_SERVER'
diff --git a/esphomeyaml/config.py b/esphomeyaml/config.py
index 75b789f901..e7a4850c4f 100644
--- a/esphomeyaml/config.py
+++ b/esphomeyaml/config.py
@@ -190,6 +190,9 @@ def _format_config_error(ex, domain, config):
     else:
         message += u'{}.'.format(humanize_error(config, ex))
 
+    if isinstance(config, list):
+        return message
+
     domain_config = config.get(domain, config)
     message += u" (See {}, line {}). ".format(
         getattr(domain_config, '__config_file__', '?'),
@@ -203,6 +206,7 @@ def load_config(path):
         config = yaml_util.load_yaml(path)
     except OSError:
         raise ESPHomeYAMLError(u"Could not read configuration file at {}".format(path))
+    core.RAW_CONFIG = config
 
     if CONF_ESPHOMEYAML not in config:
         raise ESPHomeYAMLError(u"No esphomeyaml section in config")
diff --git a/esphomeyaml/config_validation.py b/esphomeyaml/config_validation.py
index 8b9f4fd9fc..c1c9f1b211 100644
--- a/esphomeyaml/config_validation.py
+++ b/esphomeyaml/config_validation.py
@@ -3,6 +3,7 @@
 from __future__ import print_function
 
 import logging
+import re
 from datetime import timedelta
 
 import voluptuous as vol
@@ -192,30 +193,65 @@ time_period_dict = vol.All(
     lambda value: timedelta(**value))
 
 
-def time_period_str(value):
-    """Validate and transform time offset."""
+def time_period_str_colon(value):
+    """Validate and transform time offset with format HH:MM[:SS]."""
     if isinstance(value, int):
-        raise vol.Invalid("Make sure you wrap time values in quotes")
-    elif not isinstance(value, (str, unicode)):
+        raise vol.Invalid('Make sure you wrap time values in quotes')
+    elif not isinstance(value, str):
         raise vol.Invalid(TIME_PERIOD_ERROR.format(value))
 
-    value = unicode(value)
-    if value.endswith(u'ms'):
-        return vol.Coerce(int)(value[:-2])
-    elif value.endswith(u's'):
-        return vol.Coerce(float)(value[:-1]) * 1000
-    elif value.endswith(u'min'):
-        return vol.Coerce(float)(value[:-3]) * 1000 * 60
-    elif value.endswith(u'h'):
-        return vol.Coerce(float)(value[:-1]) * 1000 * 60 * 60
-    raise vol.Invalid(TIME_PERIOD_ERROR.format(value))
+    negative_offset = False
+    if value.startswith('-'):
+        negative_offset = True
+        value = value[1:]
+    elif value.startswith('+'):
+        value = value[1:]
 
-
-def time_period_milliseconds(value):
     try:
-        return timedelta(milliseconds=int(value))
-    except (ValueError, TypeError):
-        raise vol.Invalid('Expected milliseconds, got {}'.format(value))
+        parsed = [int(x) for x in value.split(':')]
+    except ValueError:
+        raise vol.Invalid(TIME_PERIOD_ERROR.format(value))
+
+    if len(parsed) == 2:
+        hour, minute = parsed
+        second = 0
+    elif len(parsed) == 3:
+        hour, minute, second = parsed
+    else:
+        raise vol.Invalid(TIME_PERIOD_ERROR.format(value))
+
+    offset = timedelta(hours=hour, minutes=minute, seconds=second)
+
+    if negative_offset:
+        offset *= -1
+
+    return offset
+
+
+def time_period_str_unit(value):
+    """Validate and transform time period with time unit and integer value."""
+    if isinstance(value, int):
+        value = str(value)
+    elif not isinstance(value, str):
+        raise vol.Invalid("Expected string for time period with unit.")
+
+    unit_to_kwarg = {
+        'ms': 'milliseconds',
+        's': 'seconds',
+        'sec': 'seconds',
+        'min': 'minutes',
+        'h': 'hours',
+        'd': 'days',
+    }
+
+    match = re.match(r"^([-+]?\d+)\s*(\w*)$", value)
+
+    if match is None or match.group(2) not in unit_to_kwarg:
+        raise vol.Invalid(u"Expected time period with unit, "
+                          u"got {}".format(value))
+
+    kwarg = unit_to_kwarg[match.group(2)]
+    return timedelta(**{kwarg: int(match.group(1))})
 
 
 def time_period_to_milliseconds(value):
@@ -223,11 +259,18 @@ def time_period_to_milliseconds(value):
         return value
     if isinstance(value, float):
         return int(value)
-    return value / timedelta(milliseconds=1)
+    return int(value.total_seconds() * 1000)
 
 
-time_period = vol.All(vol.Any(time_period_str, timedelta, time_period_dict,
-                              time_period_milliseconds), time_period_to_milliseconds)
+def time_period_to_seconds(value):
+    if value / 1000 != value // 1000:
+        raise vol.Invalid("Fractions of seconds are not supported here.")
+    return value / 1000
+
+
+time_period = vol.All(vol.Any(time_period_str_colon, time_period_str_unit, timedelta,
+                              time_period_dict),
+                      time_period_to_milliseconds)
 positive_time_period = vol.All(time_period, vol.Range(min=0))
 positive_not_null_time_period = vol.All(time_period, vol.Range(min=0, min_included=False))
 
@@ -294,17 +337,62 @@ def ipv4(value):
     return IPAddress(*parts_)
 
 
-def publish_topic(value):
-    value = string_strict(value)
-    if value.endswith('/'):
-        raise vol.Invalid("Publish topic can't end with '/'")
-    if '+' in value or '#' in value:
-        raise vol.Invalid("Publish topic can't contain '+' or '#'")
+def _valid_topic(value):
+    """Validate that this is a valid topic name/filter."""
+    if isinstance(value, dict):
+        raise vol.Invalid("Can't use dictionary with topic")
+    value = string(value)
+    try:
+        raw_value = value.encode('utf-8')
+    except UnicodeError:
+        raise vol.Invalid("MQTT topic name/filter must be valid UTF-8 string.")
+    if not raw_value:
+        raise vol.Invalid("MQTT topic name/filter must not be empty.")
+    if len(raw_value) > 65535:
+        raise vol.Invalid("MQTT topic name/filter must not be longer than "
+                          "65535 encoded bytes.")
+    if '\0' in value:
+        raise vol.Invalid("MQTT topic name/filter must not contain null "
+                          "character.")
     return value
 
 
-subscribe_topic = string_strict  # TODO improve this
-mqtt_payload = string  # TODO improve this
+def subscribe_topic(value):
+    """Validate that we can subscribe using this MQTT topic."""
+    value = _valid_topic(value)
+    for i in (i for i, c in enumerate(value) if c == '+'):
+        if (i > 0 and value[i - 1] != '/') or \
+                (i < len(value) - 1 and value[i + 1] != '/'):
+            raise vol.Invalid("Single-level wildcard must occupy an entire "
+                              "level of the filter")
+
+    index = value.find('#')
+    if index != -1:
+        if index != len(value) - 1:
+            # If there are multiple wildcards, this will also trigger
+            raise vol.Invalid("Multi-level wildcard must be the last "
+                              "character in the topic filter.")
+        if len(value) > 1 and value[index - 1] != '/':
+            raise vol.Invalid("Multi-level wildcard must be after a topic "
+                              "level separator.")
+
+    return value
+
+
+def publish_topic(value):
+    """Validate that we can publish using this MQTT topic."""
+    value = _valid_topic(value)
+    if '+' in value or '#' in value:
+        raise vol.Invalid("Wildcards can not be used in topic names")
+    return value
+
+
+def mqtt_payload(value):
+    if value is None:
+        return ''
+    return string(value)
+
+
 uint8_t = vol.All(int_, vol.Range(min=0, max=255))
 uint16_t = vol.All(int_, vol.Range(min=0, max=65535))
 uint32_t = vol.All(int_, vol.Range(min=0, max=4294967295))
diff --git a/esphomeyaml/const.py b/esphomeyaml/const.py
index 52d0453ea9..565d263273 100644
--- a/esphomeyaml/const.py
+++ b/esphomeyaml/const.py
@@ -161,6 +161,9 @@ CONF_AP = 'ap'
 CONF_CSS_URL = 'css_url'
 CONF_JS_URL = 'js_url'
 CONF_SSL_FINGERPRINTS = 'ssl_fingerprints'
+CONF_PCF8575 = 'pcf8575'
+CONF_SCAN = 'scan'
+CONF_KEEPALIVE = 'keepalive'
 
 ESP32_BOARDS = [
     'featheresp32', 'node32s', 'espea32', 'firebeetle32', 'esp32doit-devkit-v1',
diff --git a/esphomeyaml/core.py b/esphomeyaml/core.py
index 087e4ebcaf..2e696c285a 100644
--- a/esphomeyaml/core.py
+++ b/esphomeyaml/core.py
@@ -22,3 +22,4 @@ CONFIG_PATH = None
 SIMPLIFY = True
 ESP_PLATFORM = ''
 BOARD = ''
+RAW_CONFIG = None
diff --git a/esphomeyaml/helpers.py b/esphomeyaml/helpers.py
index dc8c993142..bc69279f6a 100644
--- a/esphomeyaml/helpers.py
+++ b/esphomeyaml/helpers.py
@@ -370,6 +370,18 @@ def get_gpio_pin_number(conf):
 def exp_gpio_pin_(obj, conf, default_mode):
     if isinstance(conf, int):
         return conf
+
+    if 'pcf8574' in conf:
+        hub = get_variable(conf['pcf8574'])
+        if default_mode == u'INPUT':
+            return hub.make_input_pin(conf[CONF_NUMBER],
+                                      RawExpression('PCF8574_' + conf[CONF_MODE]),
+                                      conf[CONF_INVERTED])
+        elif default_mode == u'OUTPUT':
+            return hub.make_output_pin(conf[CONF_NUMBER], conf[CONF_INVERTED])
+        else:
+            raise ESPHomeYAMLError(u"Unknown default mode {}".format(default_mode))
+
     if conf.get(CONF_INVERTED) is None:
         return obj(conf[CONF_NUMBER], conf.get(CONF_MODE))
     return obj(conf[CONF_NUMBER], RawExpression(conf.get(CONF_MODE, default_mode)),
diff --git a/esphomeyaml/pins.py b/esphomeyaml/pins.py
index f39fbe5ff4..99ccfa97f1 100644
--- a/esphomeyaml/pins.py
+++ b/esphomeyaml/pins.py
@@ -5,7 +5,7 @@ import voluptuous as vol
 import esphomeyaml.config_validation as cv
 from esphomeyaml import core
 from esphomeyaml.const import ESP_PLATFORM_ESP32, ESP_PLATFORM_ESP8266, CONF_NUMBER, CONF_MODE, \
-    CONF_INVERTED
+    CONF_INVERTED, CONF_ID, CONF_PCF8575
 
 _LOGGER = logging.getLogger(__name__)
 
@@ -72,7 +72,7 @@ def _translate_pin(value):
     except ValueError:
         pass
     if value.startswith('GPIO'):
-        return vol.Coerce(int)(value[len('GPIO'):])
+        return vol.Coerce(int)(value[len('GPIO'):].strip())
     if core.ESP_PLATFORM == ESP_PLATFORM_ESP32:
         if value in ESP32_PINS:
             return ESP32_PINS[value]
@@ -80,7 +80,7 @@ def _translate_pin(value):
             raise vol.Invalid(u"ESP32: Unknown board {} with unknown "
                               u"pin {}.".format(core.BOARD, value))
         if value not in ESP32_BOARD_TO_PINS[core.BOARD]:
-            raise vol.Invalid(u"ESP32: Board {} doesn't have"
+            raise vol.Invalid(u"ESP32: Board {} doesn't have "
                               u"pin {}".format(core.BOARD, value))
         return ESP32_BOARD_TO_PINS[core.BOARD][value]
     elif core.ESP_PLATFORM == ESP_PLATFORM_ESP8266:
@@ -90,7 +90,7 @@ def _translate_pin(value):
             raise vol.Invalid(u"ESP8266: Unknown board {} with unknown "
                               u"pin {}.".format(core.BOARD, value))
         if value not in ESP8266_BOARD_TO_PINS[core.BOARD]:
-            raise vol.Invalid(u"ESP8266: Board {} doesn't have"
+            raise vol.Invalid(u"ESP8266: Board {} doesn't have "
                               u"pin {}".format(core.BOARD, value))
         return ESP8266_BOARD_TO_PINS[core.BOARD][value]
     raise vol.Invalid(u"Invalid ESP platform.")
@@ -179,19 +179,57 @@ def pin_mode(value):
     raise vol.Invalid(u"Invalid ESP platform.")
 
 
-GPIO_PIN_SCHEMA = vol.Schema({
-    vol.Required(CONF_NUMBER): gpio_pin,
-    vol.Required(CONF_MODE): pin_mode,
-    vol.Optional(CONF_INVERTED): cv.boolean,
-})
+def pcf8574_pin(value, default_mode):
+    if 'pcf8574' not in core.RAW_CONFIG:
+        raise vol.Invalid("PCF8574 not loaded, ignore this.")
 
-GPIO_OUTPUT_PIN_SCHEMA = vol.Any(output_pin, vol.Schema({
+    if isinstance(value, (str, unicode)):
+        value = {CONF_NUMBER: value}
+
+    if not isinstance(value, dict) or not isinstance(value.get(CONF_NUMBER), (str, unicode)) or \
+            value[CONF_NUMBER].count('.') != 1:
+        raise vol.Invalid("Not PCF8574 pin")
+
+    pcf_id, pin = value[CONF_NUMBER].split('.')
+    pin = vol.Coerce(int)(pin)
+
+    pcf_conf = cv.ensure_list(core.RAW_CONFIG['pcf8574'])
+    pcf = next((conf for conf in pcf_conf if conf[CONF_ID] == pcf_id), None)
+    if pcf is None:
+        raise vol.Invalid("Unknown PCF8574 id: {}".format(pcf_id))
+
+    if pcf.get(CONF_PCF8575, False):
+        pin = vol.Range(min=0, max=15)(pin)
+    else:
+        pin = vol.Range(min=0, max=7)(pin)
+
+    mode = vol.All(vol.Coerce(str), vol.Upper)(value.get(CONF_MODE, default_mode))
+    if mode not in ['INPUT', 'INPUT_PULLUP', 'OUTPUT']:
+        raise vol.Invalid("Invalid pin mode for PCF8575: {}".format(mode))
+
+    return {
+        'pcf8574': pcf[CONF_ID],
+        CONF_NUMBER: pin,
+        CONF_INVERTED: value.get(CONF_INVERTED, False),
+        CONF_MODE: mode
+    }
+
+
+def pcf8574_output_pin(value):
+    return pcf8574_pin(value, 'OUTPUT')
+
+
+def pcf8574_input_pin(value):
+    return pcf8574_pin(value, 'INPUT')
+
+
+GPIO_OUTPUT_PIN_SCHEMA = vol.Any(output_pin, pcf8574_output_pin, vol.Schema({
     vol.Required(CONF_NUMBER): output_pin,
     vol.Optional(CONF_MODE): pin_mode,
     vol.Optional(CONF_INVERTED): cv.boolean,
 }))
 
-GPIO_INPUT_PIN_SCHEMA = vol.Any(input_pin, vol.Schema({
+GPIO_INPUT_PIN_SCHEMA = vol.Any(input_pin, pcf8574_input_pin, vol.Schema({
     vol.Required(CONF_NUMBER): input_pin,
     vol.Optional(CONF_MODE): pin_mode,
     vol.Optional(CONF_INVERTED): cv.boolean,
diff --git a/esphomeyaml/writer.py b/esphomeyaml/writer.py
index 24053715e7..769dbc628c 100644
--- a/esphomeyaml/writer.py
+++ b/esphomeyaml/writer.py
@@ -4,6 +4,7 @@ import codecs
 import errno
 import os
 
+from esphomeyaml import core
 from esphomeyaml.config import iter_components
 from esphomeyaml.const import CONF_BOARD, CONF_ESPHOMEYAML, CONF_LIBRARY_URI, CONF_NAME, \
     CONF_PLATFORM, CONF_USE_BUILD_FLAGS, ESP_PLATFORM_ESP32, ESP_PLATFORM_ESP8266
@@ -50,7 +51,7 @@ platform = {platform}
 board = {board}
 framework = arduino
 lib_deps =
-    {esphomeyaml_uri}
+    {lib_deps}
     ${{common.lib_deps}}
 build_flags =
     {build_flags}
@@ -68,7 +69,9 @@ def get_build_flags(config, key):
     for _, component, conf in iter_components(config):
         if not hasattr(component, key):
             continue
-        flags = getattr(component, key)(conf)
+        flags = getattr(component, key)
+        if callable(flags):
+            flags = flags(conf)
         if flags is None:
             continue
         if isinstance(flags, (str, unicode)):
@@ -85,12 +88,12 @@ def get_ini_content(config):
         u'env': config[CONF_ESPHOMEYAML][CONF_NAME],
         u'platform': platform,
         u'board': config[CONF_ESPHOMEYAML][CONF_BOARD],
-        u'esphomeyaml_uri': config[CONF_ESPHOMEYAML][CONF_LIBRARY_URI],
         u'build_flags': u'',
     }
     build_flags = set()
     if config[CONF_ESPHOMEYAML][CONF_USE_BUILD_FLAGS]:
         build_flags |= get_build_flags(config, 'build_flags')
+        build_flags |= get_build_flags(config, 'BUILD_FLAGS')
         build_flags.add(u"-DESPHOMEYAML_USE")
     build_flags |= get_build_flags(config, 'required_build_flags')
 
@@ -98,6 +101,31 @@ def get_ini_content(config):
     build_flags = sorted(list(build_flags))
     if build_flags:
         options[u'build_flags'] = u'\n    '.join(build_flags)
+
+    lib_deps = set()
+    lib_deps.add(config[CONF_ESPHOMEYAML][CONF_LIBRARY_URI])
+    if core.ESP_PLATFORM == ESP_PLATFORM_ESP32:
+        lib_deps |= {
+            'ArduinoOTA',
+            'Update',
+            'ESPmDNS',
+            'Wire',
+            'FS',
+            'Preferences',
+
+        }
+    elif core.ESP_PLATFORM == ESP_PLATFORM_ESP8266:
+        lib_deps |= {
+            'ESP8266WiFi',
+            'Wire',
+            'Hash',
+            'ESP8266mDNS',
+            'ArduinoOTA',
+        }
+    else:
+        raise ESPHomeYAMLError("Unsupported platform {}".format(core.ESP_PLATFORM))
+    options[u'lib_deps'] = u'\n    '.join(sorted(list(lib_deps)))
+
     return INI_CONTENT_FORMAT.format(**options)