From 6b65efd3d60bbfbac3adb0bcb73d826877f4437d Mon Sep 17 00:00:00 2001
From: Phat Nguyen <phat.nt@hotmail.com>
Date: Mon, 26 Aug 2024 20:43:48 +0700
Subject: [PATCH 1/3] fix pm2.5 compensated formula, #225

---
 src/PMS/PMS.cpp | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/src/PMS/PMS.cpp b/src/PMS/PMS.cpp
index 1d1ad1c..6bcd8ad 100644
--- a/src/PMS/PMS.cpp
+++ b/src/PMS/PMS.cpp
@@ -295,29 +295,32 @@ int PMSBase::pm25ToAQI(int pm02) {
 /**
  * @brief Correction PM2.5
  * 
+ * Formula: https://github.com/airgradienthq/arduino/issues/182
+ * 
  * @param pm25 Raw PM2.5 value
  * @param humidity Humidity value (%)
  * @return int 
  */
 int PMSBase::compensated(int pm25, float humidity) {
   float value;
+  float fpm25 = pm25;
   if (humidity < 0) {
     humidity = 0;
   }
   if (humidity > 100) {
-    humidity = 100;
+    humidity = 100.0f;
   }
 
-  if(pm25 < 30) {
-    value = (pm25 * 0.524f) - (humidity * 0.0862f) + 5.75f;
-  } else if(pm25 < 50) {
-    value = (0.786f * (pm25 / 20 - 3 / 2) + 0.524f * (1 - (pm25 / 20 - 3 / 2))) * pm25 - (0.0862f * humidity) + 5.75f;
-  } else if(pm25 < 210) {
-    value = (0.786f * pm25) - (0.0862f * humidity) + 5.75f;
-  } else if(pm25 < 260) {
-    value = (0.69f * (pm25/50 - 21/5) + 0.786f * (1 - (pm25/50 - 21/5))) * pm25 - (0.0862f * humidity * (1 - (pm25/50 - 21/5))) + (2.966f * (pm25/50 -21/5)) + (5.75f * (1 - (pm25/50 - 21/5))) + (8.84f * (1.e-4) * pm25* (pm25/50 - 21/5));
-  } else {
-    value = 2.966f + (0.69f * pm25) + (8.84f * (1.e-4) * pm25);
+  if(pm25 < 30) { /** pm2.5 < 30 */
+    value = (fpm25 * 0.524f) - (humidity * 0.0862f) + 5.75f;
+  } else if(pm25 < 50) { /** 30 <= pm2.5 < 50 */
+    value = (0.786f * (fpm25 * 0.05f - 1.5f) + 0.524f * (1 - (fpm25 * 0.05f - 1.5f))) * fpm25 - (0.0862f * humidity) + 5.75f;
+  } else if(pm25 < 210) { /** 50 <= pm2.5 < 210 */
+    value = (0.786f * fpm25) - (0.0862f * humidity) + 5.75f;
+  } else if(pm25 < 260) { /** 210 <= pm2.5 < 260 */
+    value = (0.69f * (fpm25 * 0.02f - 4.2f) + 0.786f * (1 - (fpm25 * 0.02f - 4.2f))) * fpm25 - (0.0862f * humidity * (1 - (fpm25 * 0.02f - 4.2f))) + (2.966f * (fpm25 * 0.02f - 4.2f)) + (5.75f * (1 - (fpm25 * 0.02f - 4.2f))) + (8.84f * (1.e-4) * fpm25 * fpm25 * (fpm25 * 0.02f - 4.2f));
+  } else { /** 260 <= pm2.5 */
+    value = 2.966f + (0.69f * fpm25) + (8.84f * (1.e-4) * fpm25 * fpm25);
   }
 
   if(value < 0) {

From c52962d6285a7ed2729ff43f423a803892f10553 Mon Sep 17 00:00:00 2001
From: Phat Nguyen <phat.nt@hotmail.com>
Date: Mon, 26 Aug 2024 20:47:48 +0700
Subject: [PATCH 2/3] Update float constant

---
 src/PMS/PMS.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/PMS/PMS.cpp b/src/PMS/PMS.cpp
index 6bcd8ad..450d128 100644
--- a/src/PMS/PMS.cpp
+++ b/src/PMS/PMS.cpp
@@ -314,11 +314,11 @@ int PMSBase::compensated(int pm25, float humidity) {
   if(pm25 < 30) { /** pm2.5 < 30 */
     value = (fpm25 * 0.524f) - (humidity * 0.0862f) + 5.75f;
   } else if(pm25 < 50) { /** 30 <= pm2.5 < 50 */
-    value = (0.786f * (fpm25 * 0.05f - 1.5f) + 0.524f * (1 - (fpm25 * 0.05f - 1.5f))) * fpm25 - (0.0862f * humidity) + 5.75f;
+    value = (0.786f * (fpm25 * 0.05f - 1.5f) + 0.524f * (1.0f - (fpm25 * 0.05f - 1.5f))) * fpm25 - (0.0862f * humidity) + 5.75f;
   } else if(pm25 < 210) { /** 50 <= pm2.5 < 210 */
     value = (0.786f * fpm25) - (0.0862f * humidity) + 5.75f;
   } else if(pm25 < 260) { /** 210 <= pm2.5 < 260 */
-    value = (0.69f * (fpm25 * 0.02f - 4.2f) + 0.786f * (1 - (fpm25 * 0.02f - 4.2f))) * fpm25 - (0.0862f * humidity * (1 - (fpm25 * 0.02f - 4.2f))) + (2.966f * (fpm25 * 0.02f - 4.2f)) + (5.75f * (1 - (fpm25 * 0.02f - 4.2f))) + (8.84f * (1.e-4) * fpm25 * fpm25 * (fpm25 * 0.02f - 4.2f));
+    value = (0.69f * (fpm25 * 0.02f - 4.2f) + 0.786f * (1.0f - (fpm25 * 0.02f - 4.2f))) * fpm25 - (0.0862f * humidity * (1.0f - (fpm25 * 0.02f - 4.2f))) + (2.966f * (fpm25 * 0.02f - 4.2f)) + (5.75f * (1.0f - (fpm25 * 0.02f - 4.2f))) + (8.84f * (1.e-4) * fpm25 * fpm25 * (fpm25 * 0.02f - 4.2f));
   } else { /** 260 <= pm2.5 */
     value = 2.966f + (0.69f * fpm25) + (8.84f * (1.e-4) * fpm25 * fpm25);
   }

From aafaa42a6869f9e0700f8032746fc4ec793c8de7 Mon Sep 17 00:00:00 2001
From: Phat Nguyen <phat.nt@hotmail.com>
Date: Sun, 1 Sep 2024 19:56:11 +0700
Subject: [PATCH 3/3] Update formula link

---
 src/PMS/PMS.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/PMS/PMS.cpp b/src/PMS/PMS.cpp
index 450d128..977e174 100644
--- a/src/PMS/PMS.cpp
+++ b/src/PMS/PMS.cpp
@@ -295,7 +295,7 @@ int PMSBase::pm25ToAQI(int pm02) {
 /**
  * @brief Correction PM2.5
  * 
- * Formula: https://github.com/airgradienthq/arduino/issues/182
+ * Formula: https://www.airgradient.com/documentation/correction-algorithms/
  * 
  * @param pm25 Raw PM2.5 value
  * @param humidity Humidity value (%)