Add PZEM004T/PZEMAC/PZEMDC Support (#587)

* Add PZEM004T Support

* Don't flush as much

* Update pzem004t.cpp

* Add generalized modbus

* Add PZEMAC

* Add PZEMDC

* Fix file modes

* Lint

* Fix

* Fix

* Add check_uart_settings

esphome/components/pzem004t/sensor.py

@@ -0,0 +1,37 @@
+import esphome.codegen as cg
+import esphome.config_validation as cv
+from esphome.components import sensor, uart
+from esphome.const import CONF_CURRENT, CONF_ID, CONF_POWER, CONF_VOLTAGE, \
+    UNIT_VOLT, ICON_FLASH, UNIT_AMPERE, UNIT_WATT
+
+DEPENDENCIES = ['uart']
+
+pzem004t_ns = cg.esphome_ns.namespace('pzem004t')
+PZEM004T = pzem004t_ns.class_('PZEM004T', cg.PollingComponent, uart.UARTDevice)
+
+CONFIG_SCHEMA = cv.Schema({
+    cv.GenerateID(): cv.declare_id(PZEM004T),
+
+    cv.Optional(CONF_VOLTAGE): sensor.sensor_schema(UNIT_VOLT, ICON_FLASH, 1),
+    cv.Optional(CONF_CURRENT): sensor.sensor_schema(UNIT_AMPERE, ICON_FLASH, 2),
+    cv.Optional(CONF_POWER): sensor.sensor_schema(UNIT_WATT, ICON_FLASH, 0),
+}).extend(cv.polling_component_schema('60s')).extend(uart.UART_DEVICE_SCHEMA)
+
+
+def to_code(config):
+    var = cg.new_Pvariable(config[CONF_ID])
+    yield cg.register_component(var, config)
+    yield uart.register_uart_device(var, config)
+
+    if CONF_VOLTAGE in config:
+        conf = config[CONF_VOLTAGE]
+        sens = yield sensor.new_sensor(conf)
+        cg.add(var.set_voltage_sensor(sens))
+    if CONF_CURRENT in config:
+        conf = config[CONF_CURRENT]
+        sens = yield sensor.new_sensor(conf)
+        cg.add(var.set_current_sensor(sens))
+    if CONF_POWER in config:
+        conf = config[CONF_POWER]
+        sens = yield sensor.new_sensor(conf)
+        cg.add(var.set_power_sensor(sens))