diff --git a/esphome/components/i2c/i2c.cpp b/esphome/components/i2c/i2c.cpp
index 1ead9b85c8..31c21f398c 100644
--- a/esphome/components/i2c/i2c.cpp
+++ b/esphome/components/i2c/i2c.cpp
@@ -44,7 +44,7 @@ ErrorCode I2CDevice::write_register(uint8_t a_register, const uint8_t *data, siz
 
   buffer[0] = a_register;
   std::copy(data, data + len, buffer + 1);
-  return bus_->write_readv(this->address_, buffer, len + 1, nullptr, 0);
+  return this->bus_->write_readv(this->address_, buffer, len + 1, nullptr, 0);
 }
 
 ErrorCode I2CDevice::write_register16(uint16_t a_register, const uint8_t *data, size_t len) const {
@@ -54,7 +54,7 @@ ErrorCode I2CDevice::write_register16(uint16_t a_register, const uint8_t *data,
   buffer[0] = a_register >> 8;
   buffer[1] = a_register;
   std::copy(data, data + len, buffer + 2);
-  return bus_->write_readv(this->address_, buffer, len + 2, nullptr, 0);
+  return this->bus_->write_readv(this->address_, buffer, len + 2, nullptr, 0);
 }
 
 bool I2CDevice::read_bytes_16(uint8_t a_register, uint16_t *data, uint8_t len) {
diff --git a/esphome/components/i2c/i2c_bus.h b/esphome/components/i2c/i2c_bus.h
index c234d99b5f..1acbe506a3 100644
--- a/esphome/components/i2c/i2c_bus.h
+++ b/esphome/components/i2c/i2c_bus.h
@@ -16,10 +16,10 @@ template<size_t STACK_SIZE> class SmallBufferWithHeapFallback {
  public:
   uint8_t *get(size_t size) {
     if (size <= STACK_SIZE) {
-      return stack_buffer_;
+      return this->stack_buffer_;
     }
-    heap_buffer_ = std::unique_ptr<uint8_t[]>(new uint8_t[size]);
-    return heap_buffer_.get();
+    this->heap_buffer_ = std::unique_ptr<uint8_t[]>(new uint8_t[size]);
+    return this->heap_buffer_.get();
   }
 
  private:
diff --git a/esphome/components/mqtt/mqtt_sensor.cpp b/esphome/components/mqtt/mqtt_sensor.cpp
index 2e1db1908f..032dd3b6c6 100644
--- a/esphome/components/mqtt/mqtt_sensor.cpp
+++ b/esphome/components/mqtt/mqtt_sensor.cpp
@@ -58,8 +58,13 @@ void MQTTSensorComponent::send_discovery(JsonObject root, mqtt::SendDiscoveryCon
   if (this->sensor_->get_force_update())
     root[MQTT_FORCE_UPDATE] = true;
 
-  if (this->sensor_->get_state_class() != STATE_CLASS_NONE)
+  if (this->sensor_->get_state_class() != STATE_CLASS_NONE) {
+#ifdef USE_STORE_LOG_STR_IN_FLASH
+    root[MQTT_STATE_CLASS] = (const __FlashStringHelper *) state_class_to_string(this->sensor_->get_state_class());
+#else
     root[MQTT_STATE_CLASS] = state_class_to_string(this->sensor_->get_state_class());
+#endif
+  }
 
   config.command_topic = false;
 }
diff --git a/esphome/components/sen5x/sen5x.cpp b/esphome/components/sen5x/sen5x.cpp
index 0f27ec1b10..f3222221a2 100644
--- a/esphome/components/sen5x/sen5x.cpp
+++ b/esphome/components/sen5x/sen5x.cpp
@@ -38,6 +38,7 @@ void SEN5XComponent::setup() {
       this->mark_failed();
       return;
     }
+    delay(20);  // per datasheet
 
     uint16_t raw_read_status;
     if (!this->read_data(raw_read_status)) {
diff --git a/esphome/components/sensor/sensor.cpp b/esphome/components/sensor/sensor.cpp
index e2e8302d8b..4292b8c0bc 100644
--- a/esphome/components/sensor/sensor.cpp
+++ b/esphome/components/sensor/sensor.cpp
@@ -17,7 +17,8 @@ void log_sensor(const char *tag, const char *prefix, const char *type, Sensor *o
                 "%s  State Class: '%s'\n"
                 "%s  Unit of Measurement: '%s'\n"
                 "%s  Accuracy Decimals: %d",
-                prefix, type, obj->get_name().c_str(), prefix, state_class_to_string(obj->get_state_class()), prefix,
+                prefix, type, obj->get_name().c_str(), prefix,
+                LOG_STR_ARG(state_class_to_string(obj->get_state_class())), prefix,
                 obj->get_unit_of_measurement_ref().c_str(), prefix, obj->get_accuracy_decimals());
 
   if (!obj->get_device_class_ref().empty()) {
@@ -33,17 +34,17 @@ void log_sensor(const char *tag, const char *prefix, const char *type, Sensor *o
   }
 }
 
-const char *state_class_to_string(StateClass state_class) {
+const LogString *state_class_to_string(StateClass state_class) {
   switch (state_class) {
     case STATE_CLASS_MEASUREMENT:
-      return "measurement";
+      return LOG_STR("measurement");
     case STATE_CLASS_TOTAL_INCREASING:
-      return "total_increasing";
+      return LOG_STR("total_increasing");
     case STATE_CLASS_TOTAL:
-      return "total";
+      return LOG_STR("total");
     case STATE_CLASS_NONE:
     default:
-      return "";
+      return LOG_STR("");
   }
 }
 
diff --git a/esphome/components/sensor/sensor.h b/esphome/components/sensor/sensor.h
index 507cb326b2..f3fa601a5e 100644
--- a/esphome/components/sensor/sensor.h
+++ b/esphome/components/sensor/sensor.h
@@ -33,7 +33,7 @@ enum StateClass : uint8_t {
   STATE_CLASS_TOTAL = 3,
 };
 
-const char *state_class_to_string(StateClass state_class);
+const LogString *state_class_to_string(StateClass state_class);
 
 /** Base-class for all sensors.
  *