From 87e3dcddb9fde27ed5f057dbe8308a77829c0cd8 Mon Sep 17 00:00:00 2001
From: Johann Weging <johann@weging.com>
Date: Sun, 27 May 2018 14:29:53 +0200
Subject: [PATCH] SDS0X1 take one stable reading every 3 minutes

---
 sonoff/xsns_20_novasds.ino | 37 ++++++++++++++++++++++++++++++++-----
 1 file changed, 32 insertions(+), 5 deletions(-)

diff --git a/sonoff/xsns_20_novasds.ino b/sonoff/xsns_20_novasds.ino
index 03b4965f8..a9dd180b6 100644
--- a/sonoff/xsns_20_novasds.ino
+++ b/sonoff/xsns_20_novasds.ino
@@ -31,6 +31,10 @@ TasmotaSerial *NovaSdsSerial;
 
 uint8_t novasds_type = 1;
 uint8_t novasds_valid = 0;
+uint8_t novasds_running = 1;
+uint8_t novasds_read_tick = 30;
+uint8_t novasds_wakup_tick = 179;
+uint8_t novasds_ticker = 0;
 
 struct sds011data {
   uint16_t pm100;
@@ -69,12 +73,35 @@ bool NovaSdsReadData(bool publish)
 
 void NovaSdsSecond()                 // Every second
 {
-  if (NovaSdsReadData()) {
-    novasds_valid = 10;
-  } else {
-    if (novasds_valid) {
-      novasds_valid--;
+  if (novasds_ticker < novasds_read_tick) {
+    // wake up the sensor and wait read ticks to stabalize the sensor
+    if (!novasds_running) {
+      NovaSdsStart();
+      novasds_running = 1;
     }
+
+    // drain the serial without publishing data
+    NovaSdsReadData(false);
+    novasds_ticker++;
+
+  } else if (novasds_ticker == novasds_read_tick) {
+
+    // try to take a single stable reading and sleep the sensor
+    if (NovaSdsReadData(true)) {
+      novasds_valid = 1;
+      NovaSdsStop();
+      novasds_running = 0;
+      novasds_ticker++;
+    } else {
+      novasds_valid = 0;
+    }
+
+  } else if (novasds_ticker >= novasds_wakup_tick) {
+    // reset the counter
+    novasds_ticker = 0;
+  } else {
+    // sensor is sleeping keep waiting
+    novasds_ticker++;
   }
 }