From 9a40d6ef50579f07c1119988483cb5390d6fc2b2 Mon Sep 17 00:00:00 2001
From: Otto Winter <otto@otto-winter.com>
Date: Thu, 17 Oct 2019 21:35:31 +0200
Subject: [PATCH] Integration sensor use double precision (#715)

Fixes https://github.com/esphome/issues/issues/534

Kept the RTC value as a float in order not to introduce a breaking preferences change.
---
 esphome/components/integration/integration_sensor.cpp | 10 +++++-----
 esphome/components/integration/integration_sensor.h   |  7 ++++---
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/esphome/components/integration/integration_sensor.cpp b/esphome/components/integration/integration_sensor.cpp
index 22fab290dd..f9b5a43870 100644
--- a/esphome/components/integration/integration_sensor.cpp
+++ b/esphome/components/integration/integration_sensor.cpp
@@ -45,14 +45,14 @@ std::string IntegrationSensor::unit_of_measurement() {
 }
 void IntegrationSensor::process_sensor_value_(float value) {
   const uint32_t now = millis();
-  const float old_value = this->last_value_;
-  const float new_value = value;
+  const double old_value = this->last_value_;
+  const double new_value = value;
   const uint32_t dt_ms = now - this->last_update_;
-  const float dt = dt_ms * this->get_time_factor_();
-  float area = 0.0f;
+  const double dt = dt_ms * this->get_time_factor_();
+  double area = 0.0f;
   switch (this->method_) {
     case INTEGRATION_METHOD_TRAPEZOID:
-      area = dt * (old_value + new_value) / 2.0f;
+      area = dt * (old_value + new_value) / 2.0;
       break;
     case INTEGRATION_METHOD_LEFT:
       area = dt * old_value;
diff --git a/esphome/components/integration/integration_sensor.h b/esphome/components/integration/integration_sensor.h
index 6b1f4ccf1b..2fcec069b2 100644
--- a/esphome/components/integration/integration_sensor.h
+++ b/esphome/components/integration/integration_sensor.h
@@ -51,10 +51,11 @@ class IntegrationSensor : public sensor::Sensor, public Component {
         return 0.0f;
     }
   }
-  void publish_and_save_(float result) {
+  void publish_and_save_(double result) {
     this->result_ = result;
     this->publish_state(result);
-    this->rtc_.save(&result);
+    float result_f = result;
+    this->rtc_.save(&result_f);
   }
   std::string unit_of_measurement() override;
   std::string icon() override { return this->sensor_->get_icon(); }
@@ -67,7 +68,7 @@ class IntegrationSensor : public sensor::Sensor, public Component {
   ESPPreferenceObject rtc_;
 
   uint32_t last_update_;
-  float result_{0.0f};
+  double result_{0.0f};
   float last_value_{0.0f};
 };